Heterotrophic Bacteria

1. To reveal the role of aquatic heterotrophic bacteria in the process of development of Microcystis blooms in natural waters, we cocultured unicellular Microcystis aeruginosa with a natural Microcystis-associated heterotrophic bacterial community. 2. Unicellular M. aeruginosa at different initial cell densities aggregated into colonies in the presence of heterotrophic bacteria, while axenic Microcystis continued to grow as single cells. The specific growth rate, the chl a content, the maximum electron transport rate (ETR max ) and the synthesis and secretion of extracellular polysaccharide (EPS) were higher in non-axenic M. aeruginosa than in axenic M. aeruginosa after cell aggregation, whereas axenic and non-axenic M. aeruginosa displayed the same physiological characteristic before aggregation. 3. Heterotrophic bacterial community composition was analysed by PCR-denaturing gradient gel electrophoresis (PCR-DGGE) fingerprinting. The biomass of heterotrophic bacteria strongly increased in the coinoculated cultures, but the DGGE banding patterns in coinoculated cultures were distinctly dissimilar to those in control cultures with only heterotrophic bacteria. Sequencing of DGGE bands suggested that Porphyrobacter, Flavobacteriaceae and one uncultured bacterium could be specialist bacteria responsible for the aggregation of M. aeruginosa. 4. The production of EPS in non-axenic M. aeruginosa created microenvironments that probably served to link both cyanobacterial cells and their associated bacterial cells into mutually beneficial colonies. Microcystis colony formation facilitates the maintenance of high biomass for a long time, and the growth of heterotrophic bacteria was enhanced by EPS secretion from M. aeruginosa. 5. The results from our study suggest that natural heterotrophic bacterial communities have a role in the development of Microcystis blooms in natural waters. The mechanisms behind the changes of the bacterial community and interaction between cyanobacteria and heterotrophic bacteria need further investigations.

Anaerobic methanogenic consortia have a considerable resistance to oxygen exposure. Yet, most research has been focused on the study of the tolerance to oxygen of anaerobic immobilized biomass. Less is known on the potential of the anaerobic suspended biomass for withstanding exposure to oxygen and the effect of a primary degradable substrate on such resistance. Thus, the objective of this work was to determine the effect of the amount of a primary degradable substrate (sucrose) on the resistance of a methanogenic suspended biomass to oxygen exposure. It was found that the inhibition of disperse anaerobic sludge by oxygen exposure decreases when the concentration of the supplemented carbon source increases. This is in agreement with the fact that aerobic respiration of the added substrate by the facultative heterotrophic bacteria, always present in this type of sludge, has been found in previous studies as one of the main mechanisms protecting methanogens against O2. From a practica...

In this work, the density of bacterioplankton and environmental parameters were monitored over a 11 month period (July 1999-June 2000), and also during one tidal cycle (15 June 2000), at two sampling stations, in the estuary of River Mondego. These data were treated by multivariate analyses methods in order to identify the key factors that control the dynamics of the bacterioplankton in the estuary. Bacterial dynamics were dominated by temporal gradients (annual seasons and tide-related) and less by the spatial structure of the estuary. Three main metabolic groups of bacterioplankton-aerobic heterotrophic bacteria, sulphate-reducing bacteria (SRB) and nitrate-reducing bacteria (NRB)-involved in the cycling of organic matter, were present in the water column of the estuary. Their relative abundance depended on the particular physical, chemical and biological environment. The abundance of aerobic heterotrophic bacteria, during the 11 month study, was modelled as a function of nitrate (the most important variable, with a negative effect), temperature, salinity and pH (with positive effects). SRB appeared to be limited to the water-sediment interface, where concentrations of sulphate and POM were greater. A competition between SRB and NRB for carbon has also been suggested.

An on-board microcosm experiment was set up to test the hypothesis that the observed lack of phytoplankton biomass increase response to a mesoscale in situ P-enrichment experiment in the P-limited Eastern Mediterranean (Krom et al., 2005a) was a consequence of co-limitation by P and N availability in this ultraoligotrophic environment. Six microcosms were filled with subsurface seawater (ambient DIN: 90-100 nM) taken from inside a P-enriched patch (IN), which in the absence of biological activity would have had ca. 22 nM of PO 4 . Another six microcosms were filled with unfertilized (o2 nM PO 4 À3 ) subsurface seawater from outside the patch (OUT). The bottles were either supplemented with 1600 nM NH 4 + or not, incubated on-deck and subsampled daily, or at the first and last (fourth) day of the experiment, for a suite of biological parameters. The addition of N to OUT water did not induce cell abundance increases in either the phototrophic or heterotrophic sides of the food chain, in line with previous assessments that the Eastern Mediterranean is not purely Nlimited. The IN and OUT treatments, to which no NH 4 + was added, mimicked the behavior of the in situ experiment, with an order of magnitude higher bacterial production of IN vs. OUT water, but no noticeable phytoplankton response. The addition of N to IN water, previously exposed to P, led to substantial responses of the entire microbial community, including 4 to 80-fold increases in chlorophyll, other pigments, bacterial activity, and the abundance of ciliates-relative to IN water to which N was not added. The ca. 10-fold increase in chlorophyll within 4 days was mostly due to a major increase in both abundance ( Â 4) and fluorescence per cell ( Â 17) of Synechococcus, whereas Prochlorococcus disappeared. These changes were accompanied by removal from the water of 570 nM of the added NH 4 + , equivalent to 570/22 or N : P ratio of 26 : 1, similar to the ratio measured for POM in the area. Possibly, non-Redfield ratios were maintained, still leaving by day 4 some 1100 nM of N that could not be used due to the lack of P. These results support our hypothesis that the lack of response of phytoplankton to the mesoscale P-enrichment was due to their concurrent N-starvation, i.e. N and

Heterotrophic plate count (HPC) constitutes a common indicator for monitoring of microbiological water quality in distribution systems (DS). This paper aims to identify factors explaining the spatiotemporal distribution of heterotrophic bacteria and model their occurrence in the distribution system. The case under study is the DS of Quebec City, Canada. The study is based on a robust database resulting from a sampling campaign carried out in about 50 DS locations, monitored bi-weekly over a three-year period. Models for explaining and predicting HPC levels were based on both one-level and multi-level Poisson regression techniques. The latter take into account the nested structure of data, the possible spatiotemporal correlation among HPC observations and the fact that sampling points, months and/or distribution sub-systems may represent clusters. Models show that the best predictors for spatiotemporal occurrence of HPC in the DS are: free residual chlorine that has an inverse relation with the HPC levels, water temperature and water ultraviolet absorbance, both having a positive impact on HPC levels. A sensitivity analysis based on the best performing model (two-level model) allowed for the identification of seasonal-based strategies to reduce HPC levels.

Heterotrophic plate count (HPC) constitutes a common indicator for monitoring of microbiological water quality in distribution systems (DS). This paper aims to identify factors explaining the spatiotemporal distribution of heterotrophic bacteria and model their occurrence in the distribution system. The case under study is the DS of Quebec City, Canada. The study is based on a robust database resulting from a sampling campaign carried out in about 50 DS locations, monitored bi-weekly over a three-year period. Models for explaining and predicting HPC levels were based on both one-level and multi-level Poisson regression techniques. The latter take into account the nested structure of data, the possible spatiotemporal correlation among HPC observations and the fact that sampling points, months and/or distribution sub-systems may represent clusters. Models show that the best predictors for spatiotemporal occurrence of HPC in the DS are: free residual chlorine that has an inverse relation with the HPC levels, water temperature and water ultraviolet absorbance, both having a positive impact on HPC levels. A sensitivity analysis based on the best performing model (two-level model) allowed for the identification of seasonal-based strategies to reduce HPC levels.

Aims: This study aims at isolating/enumerating microorganisms present in the plant root environment of Calopogonium mucunoides and to examine the biodiversity of rhizosphere/rhizoplane flora in different soil samples of the legume. Original Research Article Mucor spp., Penicillium spp, and Rhizopus spp. Conclusion, Significance and Impact of Study: The microorganisms seen in the rhizosphere of the plant could be used for both microbiological and biotechnological research at the University.

In this study, we determine differences in total biomass of soil microorganisms and community structure (using the most probable number of bacteria (MPN) and the number of fungal genera) in patterned ground features (PGF) and adjacent vegetated soils (AVS) in mesic sites from three High Arctic islands in order to characterize microbial dynamics as affected by cryoturbation, and a broad bioclimatic gradient. We also characterize total biomass of soil microorganisms and the most probable number of bacteria along a topographic gradient within each bioclimatic subzone to evaluate whether differences in topography lead to differences in microbial dynamics at a smaller scale. We found total microbial biomass C, the most probable number of heterotrophic bacteria, and fungal genera vary along this bioclimatic gradient. Microbial biomass C decreased with increasing latitude. Overall, microbial biomass C, MPN and the number of fungal isolates were higher in AVS than in PGFs. The effects which topographic position had on microbial biomass C varied across the bioclimatic gradient as there was no effect of topographic position in Isachsen (subzone A) and Mould Bay (subzone B), when compared to Green Cabin (subzone C, warmer site).There was no effect of topographic position on MPN counts at Mould Bay and Green Cabin. However, in Isachsen, MPN counts were highest in the wet topographic position as compared to the mesic and dry. In conclusion, PGFs seem to decouple the effect climate that might have on the total biomass of soil microorganisms along the bioclimatic gradient; and influence gets ameliorated as latitude increases. Similarly, the effect of topography on the total microbial biomass is significant at the warmest bioclimatic zone of the gradient. Thus, climate and topographic effects on total microbial biomass increase with warmer climate.

Microbial activity on food leads to its spoilage. This is usually by enzymatic processes that bring about lost of nutrients experienced on decaying food. Food decay, affect virtually all classes of nutrients in food especially, the organic aspect with proteins and lipids being the most. This study aimed at determinig the nutritional assessment and microbial safety of croaker fish from different frozen food centers. The nutritional assessment was determined through proximate analysis by standard method of AOAC and microbial safety by aerobic count, proteolytic and lipolytic count method using approprioate media. The results for proximate analysis showed moisture (62.

In this study, plastics industry wastewater (PIWW) characterized by high total and soluble chemical oxygen demand (tCOD and sCOD, up to ~2200 and ~1500 mg/L, respectively) and remarkable unbiodegradable soluble COD (usCOD, 508±224 mg/L, 31±14% of tCOD) concentrations was treated at laboratory scale using a hybrid moving bed biofilm reactor (MBBR). Interestingly, the MBBR showed average tCOD, sCOD and usCOD removal efficiencies of 26±6, 32±11 and 36±11%, respectively, which were comparable to those achieved by the coagulation/flocculation pre-treatment currently applied at full-scale. Such results encourage the application of MBBR as a cost-effective option for the removal of recalcitrant soluble organics from PIWW and other similar industrial wastewaters.

Background and Objectives: Water quality is the most important factor affecting fish health and performance in aquaculture production. This research was therefore carried out to evaluate the suitability of Omambala river in Anaku community for aquaculture purposes. Materials and Methods: Physicochemical properties, heavy metals and biological parameters were assessed to determine the suitability of the river water for aquaculture production using three different sampling stations. Data obtained were compared with the permissible limit of World Health Organization. Analytical tools used were T-test and ANOVA with SPSS Version 20. Results: The study revealed that the physiochemical parameters and heavy metal concentration were in the range of temperature, 27.33±0.57 o C, turbidity, 49.80±5.70cm, nitrate, 1.06.00±0.52mg/l, Ammonia, 0.53±0.03mg/l, pH, 6.77±0.06, Dissolved oxygen, 9.33±0.57mg/l, lead, 0.123±0.015ppm, cadmium, 0.133±0.003ppm, mercury, 0.861±0.101ppm, zinc, 0.518±0.03ppm and iron, 7.436±0.58ppm. This study revealed that the physicochemical parameters were within tolerable limit except nitrate while the heavy metals were above the tolerable limits except zinc. There were abundance of phytoplankton and zooplankton in Omambala river. Conclusion: Omambala river in Anaku fishing community is suitable for aquaculture purposes when properly treated to reduce high concentrations of heavy metals and it is recommended that proper environmental impact assessment of industrial, domestic and anthropogenic effluents into Omambala river be carried out to establish adequate detoxification measures.

Microbial communities, where Streptomyces species predominate, were found in association with hydromagnesite, Mg 5 (CO 3 ) 4 (OH)2 ¢4H 2 O, and needle-®ber aragonite deposits in an Altamira cave. The ability to precipitate calcium carbonate in laboratory cultures suggests that these and other bacteria present in the cave may play a role in the formation of moonmilk deposits.

We used a method that combines microautoradiography with hybridization of fluorescent rRNA-targeted oligonucleotide probes to whole cells (MICRO-FISH) to test the hypothesis that the relative contributions of various phylogenetic groups to the utilization of dissolved organic matter (DOM) depend solely on their relative abundance in the bacterial community. We found that utilization of even simple low-molecular-weight DOM components by bacteria differed across the major phylogenetic groups and often did not correlate with the relative abundance of these bacterial groups in estuarine and coastal environments. The Cytophaga-Flavobacter cluster was overrepresented in the portion of the assemblage consuming chitin, N -acetylglucosamine, and protein but was generally underrepresented in the assemblage consuming amino acids. The amino acid-consuming assemblage was usually dominated by the α subclass of the class Proteobacteria , although the representation of α-proteobacteria in the prote...

At this time the European Union regulations require that the heterotrophic plate counts HPC of mineral waters be assessed at two recovery temperatures: 228C for 72 h and 378C for 24 h. This procedure is time consuming and expensive. Development of new rapid methods for microbiological assessment of the microbial flora in the bottled water is an industry-driven need. The objectives of this work were to develop a method for the HPC that utilises only one recovery temperature and one incubation period and evaluate the use of, the LIVErDEAD w BacLighte Bacterial Viability Kit, 5-cyano-2,3-ditotyl Ž . tetrazolium chloride CTC and impedance methods to enumerate viable bacteria in bottled mineral water. Results showed that incubation at 308C could be used instead of incubation at 228C and 378C. Good correlation exists Ž . between counts at 308C and counts at 228C r ) 0.90 and all the pathogens important in mineral water analyses grow similarly at 308C and 378C during 24 h. It was demonstrated that impedance methods might be useful to the mineral water industry as a rapid indicator of microbiological quality of the water. Results obtained with BacLight and CTC were similar to those obtained with plate counts.

The sensitivity of coastal marine bacterioplankton to natural photosynthetically active radiation (PAR, 400-700 nm) and ultraviolet radiation (UVR, 280-400 nm) was evaluated in five experiments over a seasonal cycle in the Blanes Bay, NW Mediterranean Sea. Exposure to natural solar radiation generally inhibited bulk bacterial activities or damaged membrane integrity when irradiances were high (i.e. spring and summer experiments) and, in general, UVB (280-320 nm) accounted for most of the inhibition. When assessing activity ( 3 H-leucine uptake) at the single-cell level by microautoradiography and rRNA gene probing, seasonally varying responses and sensitivities were found among bacterial groups. While autumn and winter irradiances seemed too low to cause changes in activity, variable effects were found in spring and summer. SAR11 was consistently inhibited by UVR and PAR exposure, whereas Gammaproteobacteria and Bacteroidetes showed higher resistance. Roseobacter, Synechococcus and the NOR5 clade were occasionally photostimulated in their activity, mainly because of PAR. Our results indicate that a component of seasonality exists in the bacterial responses to solar radiation, which vary not only depending on the irradiance and the spectral characteristics, but also on the previous light history and the taxonomic composition of the community.

The effects of three selected agrochemicals on bacterial diversity in cultivated soil have been studied. The selected agrochemicals are Cerox (an insecticide), Ceresate and Paraquat (both herbicides). The effect on bacterial population was studied by looking at the total heterotrophic bacteria presence and the effect of the agrochemicals on some selected soil microbes. The soil type used was loamy with pH of 6.0-7.0. The soil was placed in opaque pots and bambara bean (Vigna subterranean) seeds cultivated in them. The agrochemicals were applied two weeks after germination of seeds at concentrations based on manufacturer's recommendation. Plant growth was assessed by weekly measurement of plant height, foliage appearance and number of nodules formed after one month. The results indicated that the diversity index (Di) among the bacteria populations in untreated soil and that of Cerox-treated soils were high with mean diversity index above 0.95. Mean Di for Ceresate-treated soil was 0.88, and that for Paraquattreated soil was 0.85 indicating low bacterial populations in these treatment-type soils. The study also showed that application of the agrochemicals caused reduction in the number of total heterotrophic bacteria population sizes in the soil. Ceresate caused 82.50% reduction in bacteria number from a mean of 40 × 10 5 cfu g -1 of soil sample to 70 × 10 4 cfu g -1 . Paraquat-treated soil showed 92.86% reduction, from a mean of 56 × 10 5 cfu g -1 to 40 × 10 4 cfu g -1 . Application of Cerox to the soil did not have any remarkable reduction in bacterial population number. Total viable cell count studies using Congo red yeast-extract mannitol agar indicated reduction in the number of Rhizobium spp. after application of the agrochemicals. Mean number of Rhizobium population numbers per gram of soil was 180 × 10 4 for the untreated soil. Cerox-treated soil recorded mean number of 138 × 10 4 rhizobial cfu g -1 of soil, a 23.33% reduction. Ceresate-and Paraquat-treated soils recorded 20 × 10 4 and 12 × 10 4 cfu g -1 of soil, respectively, representing 88.89% and 93.33% reduction in Rhizobium population numbers. Correspondingly, the mean number of nodules per plant was 44 for the growth in untreated soil, 30 for the plant in the Cerox-treated soil, 8 for the plant in Paraquat-treated soil and 3 for the plant in Ceresate-treated soil. The study has confi rmed detrimental effect of insecticide on bacterial populations in the soil. Total heterotrophic counts, rhizobial counts as well as the number of nodules of all samples taken from the chemically treated soils were all low as compared to values obtained for the untreated soil. However, the effect of the insecticide was minimal in all cases as compared to the effects of the herbicides on the soil fauna. Indiscriminate use of agrochemicals on farms can therefore affect soil fl ora and subsequently food production.

The contribution of heterotrophic bacteria to paniculate light absorption in the ocean has been traditionally considered insignificant as compared to that of phytoplankton and detritus. This view has been based on the general presumption that heterotrophic marine bacteria do not contain pigments with significant absorption in the visible spectral range. However, there exist heterotrophic bacteria that synthesize carotenoid pigments, and carotenoid-rich strains of bacteria have often been isolated from natural seawater samples taken in the open and coastal ocean. Because carotenoids absorb strongly in the blue spectral region, the heterotrophic bacteria may contribute more to marine light absorption than has been assumed. In order to make preliminary assessment of such a contribution, we measured the absorption of a strain of carotenoid-containing heterotrophic bacteria (CHB) grown in the laboratory under differing conditions of light and nutrient availability. These measurements showed that absorption cross-sections of CHB in the blue could be at least twice, and possibly one order of magnitude, higher than those of non-pigmented heterotrophic bacteria (NHB). In addition, the absorption features of CHB were conserved under the differing light and nutrient conditions. We conclude that the role of heterotrophic bacteria in marine light absorption needs to be re-evaluated. This will require further laboratory studies to quantify the absorption cross-sections of marine bacteria with improved accuracy, as well as the development of a technique for the recognition and enumeration of CHB cells in the ocean.

It has been demonstrated that ELF97-phosphate (ELF-P) is a useful tool to detect and quantify phosphatase activity of phytoplankton populations at a single cell level. Recently, it has been successfully applied to marine heterotrophic bacteria in culture samples, the cells exhibiting phosphatase activity being detected using epifluorescence microscopy. Here, we describe a new protocol that enables the detection of ELF alcohol (ELFA), the product of ELF-P hydrolysis, allowing the detection of phosphatase positive bacteria, using flow cytometry. Bacteria from natural samples must be disaggregated and, in oligotrophic waters, concentrated before they can be analyzed by flow cytometry. The best efficiency for disaggregating/separating bacterial cell clumps was obtained by incubating the sample for 30 min with Tween 80 (10 mg l -1 , final concentration). A centrifugation step (20,000 g; 30 min) was required in order to recover all the cells in the pellet (only 7 ± 2% of the cells were recovered from the supernatant). The cells and the ELFA precipitates were resistant to these treatments. ELFA-labelled samples were stored in liquid nitrogen for up to four months before counting without any significant loss in total or ELFA-labelled bacterial cell abundance or in the ELFA fluorescence intensity. We describe a new flow cytometry protocol for detecting and discriminating the signals from both ELFA and different counterstains (4',6-diamidino-2-phenylindole (DAPI) and propidium iodide (PI)) necessary to distinguish between ELFA-labelled and non ELFA-labelled heterotrophic bacteria. The method has been successfully applied in both freshwater and marine samples. This method promises to improve our understanding of the physiological response of heterotrophic bacteria to P limitation.

The biogeochemistry of carbon and nutrients (N,P) in the surface layer of the ocean strongly depends on the complex interactions between primary producers (phytoplankton) and remineralizers (heterotrophic bacteria). To understand how these interactions impact the overall DOC dynamics in the surface layer of the Mediterranean Sea, we implemented, using Eco3M (Ecological Mechanistic Modular Modelling tool), a multi-element model with a mechanistic description of primary production. We studied the model steady state results under various nutrient conditions and fixed cell abundances. By doing so, we show how the bottom up control of osmotrophs growth can impact the overall DOC dynamics in the system. Based on our set of parameters, the biogeochemical characteristics displayed by the model appear realistic when compared to literature data for the Mediterranean basin. Differences in DOC dynamics between N and P limited systems in the model, lead to the conclusion that the unusually high N:P ratio of the Mediterranean Sea may favour the uncoupling between growth and carbon production leading to higher DOC accumulation compared to systems with lower N:P ratio. Acknowledgements. This is a contribution of the BOUM (Biogeochemistry from the Oligotrophic to the Ultraoligotrophic Mediterranean) experiment () of the french national LEFE-CYBER program, the european IP SESAME and the international IMBER project. The BOUM experiment was coordinated by the

Two adjacent paddies of an experimental rice field, subjected to organic and conventional farming, were characterized aiming the comparative assessment of microbiological variations occurring in the bulk paddy soil over the rice cycle. This study comprehended the simultaneous characterization of general physicochemical soil properties [total carbon and nitrogen, pH (H 2 O and KCl), C:N ratio and water content], biochemical properties [enzymatic activities and Community Level Physiological Profiles (CLPP)], the estimation of cultivable organisms (enumeration of fast growing heterotrophic bacteria, actinomycetes and fungi) and the assessment of bacterial diversity using a culture-independent method (PCR-DGGE fingerprinting). The linkage of the parameters measured was analysed by canonical correspondence analysis (CCA). CCA ordination plots of the CLPP showed a similar pattern of microbial functional activity in both agronomic management systems, except in June. Enzymatic activity, water content and fungi counts were the main factors affecting the observed CLPP time variation. Such a variation was not expressed by the Shannon and evenness indices, which did not evidence significant differences in the bacterial and functional diversity between or within farming type over the analysed period. The cluster and CCA analyses of the DGGE profiles allowed the distinction of the bacterial communities of both paddies, with temporal variations being observed in the organically managed field but not in the conventional paddy. Enzymatic activity, pH and molinate content were the factors which most contributed to the observed variations. Altogether these results underline the functional redundancy of the rice paddy soil and evidence the temporal variations on the metabolic activity of soil, irrespective of farming type.

The ecological role of heterotrophic bacteria in the microbial food web of the Southern Ocean is unresolved. A coupling between phytoplankton and bacterial production is well documented in mid-to low-latitude oceans (e.g., Cole, Findlay and Pace1988) and is thought to result from the heterotrophic uptake of dissolved organic carbon (DOC) released by the primary producers (i.e. the "microbial loop;" Pomeroy 1974; Bjørnsen 1988). In Antarctic waters, however, the extent to which bacteria rely on phytoplankton production, and consequently contribute to total ecosystem production, is disputed. A positive correlation between algal and bacterial biomass has been observed in regions of the Southern Ocean (e.g., . Conversely, variability in the strength of this correlation, and even an uncoupling of algae and bacteria, has also been documented (e.g. . Accurate characterization of the microbial loop in the Southern Ocean requires quantification of algal and bacterial biomass and activity over a seasonal time scale and in the diversity of marine habitats that surround Antarctica. This necessitates that bacteria-algae associations in the pelagic environment should not be studied apart from similar associations in the sea ice that is a prominent feature of most antarctic waters.

Inappropriate dumping of solid waste at unscientific disposal sites poses a significant problem for urban areas in many developing countries. Tebela Town Administration (TTA), located in the Wolaita zone of South Ethiopia, spans 4206.9 ha and had a population of 43,608 in 2018. Currently, TTA lacks a sanitary landfill that meets scientific and environmental standards. As a result, communities have resorted to haphazardly dumping waste around homes, into rivers, ditches, and near roads, leading to serious health and environmental hazards. To address this issue, the study aims to identify suitable solid waste disposal sites using GIS technology, ensuring environmental sustainability and public health protection. Key factors considered in the site selection process include slope, faults, soil classes, and proximity to settlements, roads, rivers, and water surfaces. Weightings were assigned to each criterion based on their relative importance using the Analytic Hierarchy Process (AHP), a multi-criteria evaluation method. These weights were then integrated into GIS for overlay analysis. Results revealed that 2.81 % (118.21 ha) of the area is highly suitable, 18 % (757.20 ha) is suitable, 41.23 % (1734.5 ha) is moderately suitable, while 36.77 % (1546.88 ha) is unsuitable for landfill sites. Four potential sites were identified that meet scientific and environmental criteria, primarily located in the western, northern, northeastern, and southwestern edges of the town.

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Hemodialysis is the treatment of chronic renal failure that can increase patients’ longevity, but the change in lifestyle and various treatments lead to numerous psychological problems, such as anxiety in patients. The purpose of this study was to determine the prevalence of anxiety in patients undergoing hemodialysis in Shohadaye  Ashayer and Shahid Rahimi Hospitals in Khorramabad city. In this descriptive, analytical cross-sectional study, all eligible patients undergoing hemodialysis (n=74) were studied. The data collection tools include Spielbergers' anxiety questionnaire. Data analysis was carried out using chi-square tests, t-test, Pearson correlation, and analysis of variance. The mean state anxiety score was 50.08(10.49) and the mean trait anxiety score was 49.24(11.52). About 44.5% of the patients had severe state anxiety, and 40.5% had severe trait anxiety. The results of this study showed that women have higher levels of trait anxiety than men (p=0.014). The hemodialyzed patients in Khorramabad city had high trait and state anxiety. Therefore, it is suggested that various methods of reducing anxiety in these patients should be used.

Copahue Thermal Center is characterized by the presence of mineromedicinal acidic waters with high temperatures, therapeutic peloids, and relevant consortia of extremophiles species, distributed in small natural pools which cannot be disinfected. The objective of this research was to investigate the survival of SARS-CoV-2 in Copahue’s waters and its remaining infective capacity. In a first assay, a decrease of more than 50% of the initially viral load compared to the initially inoculated positive sample was detected for all the water samples analyzed. After that, two of the Copahue springs, which are used as an immersion bath in closed environments without going through any disinfection treatment, was selected to determine the viral viability. VERO cell infections were performed, with no cytopathic effect detected, but a strikingly high resistance of the virus, detecting its genome by real time PCR, during the seven days of study under laboratory conditions. SARS-CoV-2 survival in a...

It has been hypothesized that, by specifically lysing numerically dominant host strains, the virioplankton may play a role in maintaining clonal diversity of heterotrophic bacteria and phytoplankton populations. If viruses selectively lyse only those host species that are numerically dominant, then the number of a specific virus within the virioplankton would be expected to change dramatically over time and space, in coordination with changes in abundance of the host. In this study, the abundances of specific viruses in Chesapeake Bay water samples were monitored, using nucleic acid probes and hybridization analysis. Total virioplankton in a water sample was separated by pulsed-field gel electrophoresis and hybridized with nucleic acid probes specific to either single viral strains or a group of viruses with similar genome sizes. The abundances of specific viruses were inferred from the intensity of the hybridization signal. By using this technique, a virus comprising 1/1,000 of the...

The e ects of aldrin at rates 10 and 50 mg ml -1 on microbial function were studied under aerobic conditions. Parameters monitored included total culturable population of heterotrophic bacteria, number of culturable phosphate-solubilizing micro ora, number of bacteria which decompose protein with liberation of H2S, nitrifying bacteria, denitrifying bacteria and denitriÿcation activity. Culturable heterotrophic bacteria, phosphate-solubilizing bacteria, bacteria which decompose proteins with liberation of H2S and denitrifying bacteria were signiÿcantly increased at dose rates of 10 and 50 mg ml -1 of aldrin. However, the presence of aldrin decreased denitriÿcation activity at concentration of 50 mg ml -1 . Nitrifying population were not a ected as a consequence of the addition of aldrin, showing that these microorganisms can tolerate the concentrations of aldrin tested.

Microbe-mineral associations in regolith overlying granodiorite bedrock (4.6-4.9 m depth) 1 from the Luquillo Experimental Forest, Puerto Rico, were imaged with confocal scanning 2 laser microscopy at a novel scale of 400X magnification. After adding BacLight™ stain, 3 proportionally more surface area of minerals (quartz, biotite, and mixed opaque 4 kaolinite/goethite) emitted fluorescence from cell-impermeant propidium iodide than from 5 cell-permeant SYTO 9, which suggested greater coverage of minerals by extracellular DNA 6 or DNA in non-intact cells than by intact cells. Microscopic observations of predominantly 7 non-intact cell material in deep saprolite were consistent with the abundance of rRNA 8 sequences related to heterotrophic bacteria in clone libraries prepared from community DNA. 9 A few sequences were affiliated with bacteria recognized to produce siderophores, oxidize 10 Fe(II), or fix N 2 . Bacterial DNA in deep regolith from two boreholes 1.5 m apart yielded 11 libraries with high diversity and taxa specific for each borehole. 12

Rhizospheric soil samples were taken from Puna native grasses along an altitudinal gradient. Biodiversity of arbuscular mycorrhizal fungi (AMF) and associated bacteria was analyzed considering altitude and grasses photosynthetic pathways (metabolic type C 3 , C 4 ). Cultivation-dependent approaches were applied to obtain further information about the phylogeny of the dominating cultivable aerobic-heterotrophic bacteria communities present in rhizospheric soil samples. In average, the bacterial count ranged between 1.30×10 2 and 8.66×10 4 CFU g -1 of dry weight of soil. Individual bacterial colonies of aerobic heterotrophic bacteria grown on R2A medium were morphologically grouped and identified as typical soil bacteria belonging to the genera Bacillus, Pseudomonas, and Arthrobacter.

Mangroves are highly productive marine ecosystems where bacteria (culturable and nonculturable) actively participate in biomineralization of organic matter and biotransformation of minerals. This study explores spatial and seasonal fluctuations of culturable heterotrophic bacteria and Vibrio spp. in the sediments of an intact mangrove ecosystem and determines the dominant environmental factors that govern these fluctuations. Sediment samples were collected monthly from three stations in the mangroves of Laguna de Balandra, Baja California Sur, Mexico, through an annual cycle. Physicochemical parameters included seawater temperature, salinity, and concentration of dissolved oxygen. Viable counts of culturable heterotrophic bacteria and Vibrio spp. were made. In one sample (March 2003), nutrient concentrations (ammonium, nitrites, nitrates, and phosphates), organic matter, pH and sediment texture were also determined. General cluster analyses, analysis of variance of specific variables, and several principal component analyses demonstrated that seawater temperature is the principal determinant of seasonal distribution of culturable heterotrophic bacteria and Vibrio spp. in mangrove sediments. Soil texture, concentration of nutrients, and organic matter concentration contribute to heterogenicity to a lesser extent. A large spatial variation in bacterial populations was observed over short distances ($1 m) in sampling areas within the same site. These analyses show that the culturable bacterial distribution in sediments of mangroves has high spatial and temporal heterogeneity.

The use of riverine dissolved organic matter by the heterotrophic bacteria associated with a culture of the cyanobacterium Microcystis aeruginosa and release of simple nitrogen compounds were studied in an experimental series. Bacteria reduced the bulk of dissolved organic nitrogen (DON) by half, but when associated with M. aeruginosa, DON was excreted and its concentration rose by 13%. During the stationary growth phase bacteria released ammonium, doubling the concentration of ammonia as well as of nitrates. Bacteria associated with M. aeruginosa consumed riverine DON and joined the ammonification and nitrification process, supplying cyanobacteria with simple nitrogen compounds.

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Water samples were collected in August 2001 and 2002 from the eutrophic Lake Joutikas during cyanobacterial blooms. DNA and RNA were isolated from size fractionated samples and the diversity of the bacteria present in each fraction was studied by PCR amplification of partial 16S rRNA and denaturing gradient gel electrophoresis (DGGE) fingerprinting. Major bands from the gels were sequenced for further identification. Cyanobacteria were also identified and counted under the microscope. Anabaena/Aphanizomenon were the most abundant cyanobacteria in both years, although the dominant species was different each year. When comparing the 2 techniques, equal numbers of abundant Anabaena/Aphanizomenon morphotypes were detected by microscopy and phylotypes by DGGE. The genera Microcystis and Synechococcus appeared more abundant in the DGGE analysis than under the microscope. In the heterotrophic bacterial community variation was observed between the bloom samples from the 2 years. Verrucomicrobia was the most abundant group in both years in both DNA-and RNA-derived profiles. Otherwise the patterns based on DNAand RNA-derived DGGE-profiles differed, especially in 2002. The presence of Actinobacteria and Chloroflexi was less pronounced in RNA-based than in DNA-based analysis. This indicates that their relative biomass was smaller than estimated by DNA-analysis. It might also indicate that they were metabolically inactive. In contrast, in 2002, the CFB group (Cytophaga-Flavobacterium-Bacteroides) and δ-Proteobacteria were more prominent in the RNA-based than in the DNA-based profiles. Thus they probably formed a substantial fraction of biomass and/or were active members in the blooms.

Antibiotic-resistant bacteria and genes enter the environment in different ways. The release of these factors into the environment has increased concerns related to public health. The aim of the study was to evaluate the antibiotic resistance genes (ARGs) in the environmental resources. In this systematic review, the data were extracted from valid sources of information including ScienceDirect, PubMed, Google Scholar and SID. Evaluation and selection of articles were conducted on the basis of the PRISMA checklist. A total of 39 articles were included in the study, which were chosen from a total of 1249 papers. The inclusion criterion was the identification of genes encoding antibiotic resistance against the eight important groups of antibiotics determined by using the PCR technique in the environmental sources including municipal and hospital wastewater treatment plants, animal and agricultural wastes, effluents from treatment plants, natural waters, sediments, and drinking waters. ...

The stored metallurgy wastes contain residues from ore processing operations that are characterized by relatively high concentrations of heavy metals. The bioleaching process makes use of bacteria to recover elements from industrial wastes and to decrease potential risk of environmental contamination. Wastes were treated by solutions containing bacteria. In this work, the optimized six-stage sequential extraction procedure was applied for the fractionation of Ni, Cr, Fe, Mn, Cu and Zn in iron-nickel metallurgy wastes deposited in Southern Poland (Szklary). Fractionation and total concentrations of elements in wastes before and after various bioleaching treatments were studied. Analyses of the extracts were performed by ICP-MS and FAAS. To achieve the most effective bioleaching of Zn, Cr, Ni, Cu, Mn, Fe the usage of both autotrophic and heterotrophic bacteria in sequence, combined with flushing of the residue after bioleaching is required. 80-100% of total metal concentrations were mobilized after the proposed treatment. Wastes treated according to this procedure could be deposited without any risk of environmental contamination and additionally the metals could be recovered for industrial purposes.

Effects of elevated water temperatures and residual chlorine from a thermal discharge at a coastal nuclear power plant on the biomass and productivity of periphyton and phytoplankton were determined in subtropical Taiwan. Phytoplankton chlorophyll a, but not productivity, was significantly lower in the outlet region than in the intake region. Periphyton chlorophyll a was significantly greater in the outlet region than in the intake region. Nevertheless, periphyton productivity was negatively correlated with water temperature in the outlet region. A distinct difference in periphyton community composition was also detected between the two regions. Chlorination experiments showed that a chlorine concentration of 0.2 ppm greatly suppressed phytoplankton productivity, regardless of whether the water temperature was elevated or not. However, periphyton productivity was little influenced by a chlorine concentration of b 0.5 ppm. Our results suggest that phytoplankton productivity was greatly affected by residual chlorine, but periphyton productivity was more affected by elevated water temperatures.

The ammonia-oxidizing prokaryote (AOP) community in three groundwater treatment plants and connected distribution systems was analyzed by quantitative real-time PCR and sequence analysis targeting the amoA gene of ammonia-oxidizing bacteria (AOB) and archaea (AOA). Results demonstrated that AOB and AOA numbers increased during biological filtration of ammonia-rich anoxic groundwater, and AOP were responsible for ammonium removal during treatment. In one of the treatment trains at plant C, ammonia removal correlated significantly with AOA numbers but not with AOB numbers. Thus, AOA were responsible for ammonia removal in water treatment at one of the studied plants. Furthermore, an observed negative correlation between the dissolved organic carbon (DOC) concentration in the water and AOA numbers suggests that high DOC levels might reduce growth of AOA. AOP entered the distribution system in numbers ranging from 1.5 × 10 3 to 6.5 × 10 4 AOPs ml −1 . These numbers did not change during...

Copepod fecal pellet (fp) dissolved organic matter is consumed by free-living bacteria, while particulate matter is degraded by bacteria packed inside the fp ('internal') or attached to the fp surface after colonization from the environment (external). This study analyzed the contribution of 'internal' and external fp bacteria to the active bacterial community associated with the fp from 2 copepod species, Paramphiascella fulvofasciata and Platychelipus littoralis, during 60 h of fp aging in seawater. Despite early colonization (within 20 to 40 h), fp enrichment by seawater bacteria, as deduced from RNA-based DGGE after 60 h, was limited. In contrast, 'internal' bacteria showed high phylotype richness. The majority of 'internal' bacterial phylotypes persisted on aged fp and together represented half of the active bacterial community. Food source strongly impacted 'internal' bacterial diversity, though the exact origin of fp 'internal' bacteria, as either undigested food-associated bacteria or as copepod gut bacteria, could not be unambiguously determined. 'Internal' bacteria of fresh fp showed a high functional diversity (based on Biolog assays) to which Vibrio sp. contributed significantly. In terms of bacterial diversity and functional potential, degradation of copepod fp by 'internal' bacteria is equally as important as degradation by bacteria which colonize fp from the outside.

The predicted rise in anthropogenic CO 2 emissions will increase CO 2 concentrations and decrease seawater pH in the upper ocean. Recent studies have revealed effects of pCO 2 induced changes in seawater chemistry on a variety of marine life forms, in particular calcifying organisms. To test whether the predicted increase in pCO 2 will directly or indirectly (via changes in phytoplankton dynamics) affect abundance, activities, and community composition of heterotrophic bacteria during phytoplankton bloom development, we have aerated mesocosms with CO 2 to obtain triplicates with three different partial pressures of CO 2 (pCO 2 ): 350 µatm (1×CO 2 ), 700 µatm (2×CO 2 ) and 1050 µatm (3×CO 2 ). The development of a phytoplankton bloom was initiated by the addition of nitrate and phosphate. In accordance to an elevated carbon to nitrogen drawdown at increasing pCO 2 , bacterial production (BPP) of free-living and attached bacteria as well as cell-specific BPP (csBPP) of attached bacteria were related to the C:N ratio of suspended matter. These relationships significantly differed among treatments. However, bacterial abundance and activities were not statistically different among treatments. Solely community structure of free-living bacteria changed with pCO 2 whereas that of attached bacteria seemed to be independent of pCO 2 but tightly coupled to phytoplankton bloom development. Our findings imply that changes in pCO 2 , although reflected by changes in community structure of free-living bacteria, do not directly affect bacterial activity. Furthermore, bacterial activity and dynamics of heterotrophic bacteria, especially of attached bacteria, were tightly linked to phytoplankton development and, hence, may also potentially depend on changes in pCO 2 .

In order to recover as many viable bacteria as possible from natural mineral water, in this study we have compared the counts obtained with the standard method (pour plate procedure with Plate Count Agar (PCA)) and counts with alternative test methods (PCA/spread plates, R2A medium/pour plates and R2A medium/spread plates). The results showed that counts with R2A medium/spread plates at

The effects of chloramphenicol and streptomycin/penicillin on the concentration of heterotrophic bacteria in biofilms associated with abalone postlarval culture and on the growth and survival of Haliotis rufescens postlarvae (3-5 days old) were studied under laboratory conditions. Two experiments were carried out in 12-well polystyrene tissue culture plates with 5 mL of 1-mm-filtered autoclaved seawater. Water was changed every other day and antibiotics were added during the water change. Experimental units were previously inoculated with the benthic diatom Navicula incerta. In the first experiment chloramphenicol at 0, 5, 10, and 20 mg L -1 was used and a mixture of streptomycin and penicillin at 0/0, 50/50, 100/100, and 150/150 mg L -1 was tested in the second experiment (in both cases with three replicates). Bacterial counts (Zobell plates) were performed for a period of 4 and 5 wk (experiments 1 and 2, respectively). Bacterial densities decreased 90% in 20 mg L -1 of chloramphenicol during the first 48 h; however, bacterial counts increased in all treatments thereafter and differences were not significant at the end of the experiment. The growth of abalone postlarvae was not significantly different among treatments. In the experiment with antibiotic mixtures, bacterial abundance was reduced 99% at the highest concentration (150/150) in the first 48 h, and remained significantly lower than the control for 2-3 wk. During this period, postlarval growth in this antibiotic treatment was also slower, as well as final survival, suggesting an important role of bacteria in the nutrition and/or digestion of abalone postlarvae. Results of this study also suggest that bacterial resistance to these antibiotics develops fast, discouraging their long-term use in abalone culture.

Pearson's Product-Moment correlation analysis of the relationships between total hydrocarbon content (THC) and hydrocarbon utilizing bacteria population (HUB) in mangrove sediments and overlying water of the Qua Iboe Estuary, Nigeria was carried out. The results show that there was in general a close relationship between the two variables, but also a large amount of variation not explained by the analysis. The strongest positive relationships (p = 0.05) were found for THC in epipellic (intertidal) sediment and water (r = 0.65) while the relationship between THC in benthic (subtidal) sediment and water (r = 0.028) was weak, and positively insignificant (p = 0.05). A correlation of HUB densities on THC in benthic sediment was strong and positive (r = 0.91) but characterized by high HUB/HET ratios. That is, the strength of the relationship with respect to the oil degrading potentials of the bacterial was fairly low. In contrast, the relationships between the two variables in epipellic sediment (r = 0.66) was positively significant (p = 0.05) but with a substantial presence of heterotrophic bacteria. This implies that a quick-analysis of hydrocarbon content in epipellic sediment in relation to hydrocarbon utilizing bacteria densities following an oil spill is reliable. However, such analysis on benthic sediment may not be reliable in estuarine environment with chronic exposure to crude oil pollution. This is despite the wide distribution of HUB (82.4% in benthic sediment, 43.1% in epipellic sediment, and 33.3% in surface water) in the ecosystem as revealed by the coefficient of determinations (R 2

Tolerance to Zn 2+ by pure cultures of Bacillus, Salmonella and Arthrobacter species isolated from New Calabar River sediment was assessed through dehydrogenase assay. The cultures were exposed to Zn 2+ concentrations of 0.2 to 2.0 mM in a nutrient broth-glucose-TTC medium. The responses of the bacterial strains varied with Zn 2+ concentration. In Salmonella sp. SED2, Zn 2+ stimulated dehydrogenase activity at 0.2 mM. In Bacillus sp. SED1 and Arthrobacter sp. SED4, dehydrogenase activity was progressively inhibited with increasing Zn 2+ concentration. The IC 50 ranges from 0.206 ± 0.030 to 0.807 ± 0.066 mM. Total inhibition of dehydrogenase activity was observed at concentrations ranging from 1.199 ± 0.042 to 1.442 ± 0.062. The order of zinc tolerance is: Salmonella sp. SED2 > Arthrobacter sp. SED4 > Bacillus sp. SED1. The result of the in vitro study indicated that Zinc is potentially toxic to sediment bacteria and could pose serious threat to their metabolism in natural environments.

High-nucleic-acid (HNA) and low-nucleic-acid (LNA) bacteria are two operational groups identified by flow cytometry (FCM) in aquatic systems. A number of reports have shown that HNA cell density correlates strongly with heterotrophic production, while LNA cell density does not. However, which taxa are specifically associated with these groups, and by extension, productivity has remained elusive. Here, we addressed this knowledge gap by using a machine learning-based variable selection approach that integrated FCM and 16S rRNA gene sequencing data collected from 14 freshwater lakes spanning a broad range in physicochemical conditions. There was a strong association between bacterial heterotrophic production and HNA absolute cell abundances (R 2 ϭ 0.65), but not with the more abundant LNA cells. This solidifies findings, mainly from marine systems, that HNA and LNA bacteria could be considered separate functional groups, the former contributing a disproportionately large share of carbon cycling. Taxa selected by the models could predict HNA and LNA absolute cell abundances at all taxonomic levels. Selected operational taxonomic units (OTUs) ranged from low to high relative abundance and were mostly lake system specific (89.5% to 99.2%). A subset of selected OTUs was associated with both LNA and HNA groups (12.5% to 33.3%), suggesting either phenotypic plasticity or within-OTU genetic and physiological heterogeneity. These findings may lead to the identification of system-specific putative ecological indicators for heterotrophic productivity. Generally, our approach allows for the association of OTUs with specific functional groups in diverse ecosystems in order to improve our understanding of (microbial) biodiversity-ecosystem functioning relationships. IMPORTANCE A major goal in microbial ecology is to understand how microbial community structure influences ecosystem functioning. Various methods to directly associate bacterial taxa to functional groups in the environment are being developed. In this study, we applied machine learning methods to relate taxonomic data obtained from marker gene surveys to functional groups identified by flow cytometry. This allowed us to identify the taxa that are associated with heterotrophic productivity in freshwater lakes and indicated that the key contributors were highly system specific, regularly rare members of the community, and that some could possibly switch between being low and high contributors. Our approach provides a promising framework to identify taxa that contribute to ecosystem functioning and can be further developed to explore microbial contributions beyond heterotrophic production.