Biología funcional

Despite the fact that most industrial processes for secondary metabolite production are performed with submerged cultures, a reliable developmental model for Streptomyces under these culture conditions is lacking. With the exception of a few species which sporulate under these conditions, it is assumed that no morphological differentiation processes take place. In this work, we describe new developmental features of Streptomyces coelicolor A3(2) grown in liquid cultures and integrate them into a developmental model analogous to the one previously described for surface cultures. Spores germinate as a compartmentalized mycelium (first mycelium). These young compartmentalized hyphae start to form pellets which grow in a radial pattern. Death processes take place in the center of the pellets, followed by growth arrest. A new multinucleated mycelium with sporadic septa (second mycelium) develops inside the pellets and along the periphery, giving rise to a second growth phase. Undecylprodigiosin and actinorhodin antibiotics are produced by this second mycelium but not by the first one. Cell density dictates how the culture will behave in terms of differentiation processes and antibiotic production. When diluted inocula are used, the growth arrest phase, emergence of a second mycelium, and antibiotic production are delayed. Moreover, pellets are less abundant and have larger diameters than in dense cultures. This work is the first to report on the relationship between differentiation processes and secondary metabolite production in submerged Streptomyces cultures.

Vital stains were used in combination with fluorimetry for the elaboration of a new method to quantify Streptomyces programmed cell death, one of the key events in Streptomyces differentiation. The experimental approach described opens the possibility of designing online protocols for automatic monitoring of industrial fermentations.

Bacteria of the genus Streptomyces are a model system for bacterial multicellularity. Their mycelial life style involves the formation of long multinucleated hyphae during vegetative growth, with occasional cross-walls separating long compartments. Reproduction occurs by
specialized aerial hyphae, which differentiate into chains of uninucleoid spores. While the tubulin-like FtsZ protein is required for the formation of all peptidoglycan-based septa in Streptomyces, canonical divisome-dependent cell division only occurs during sporulation. Here we report extensive subcompartmentalization in young vegetative hyphae of Streptomyces coelicolor, whereby 1 mm compartments are formed by nucleic acid stain-impermeable barriers. These barriers possess the permeability properties of membranes and at least some of them are cross-membranes without detectable peptidoglycan. Z-ladders form during the early growth, but cross-membrane formation does not depend on FtsZ. Thus, a new level of hyphal organization is presented involving unprecedented high-frequency compartmentalization,
which changes the old dogma that Streptomyces vegetative hyphae have scarce compartmentalization.

Atlantic salmon stocks in northern Spain are at the southern range of the species distribution. As such they are likely more vulnerable to environmental change and human disturbance. The Nalon-Narcea River salmon is one such population in Asturias, Spain. The river is dammed throughout the watershed with few fish passage facilities. However, angling data show that salmon returns are consistent although the population is relatively small. We have employed one tributary as a model, the River Trubia. Although some problems of agriculture and industrial pollution have been detected downstream, an upstream habitat evaluation suggests that adequate spawning and juvenile habitat exists. The regional Government has proposed to construct fishways for allowing upstream passage of salmon. This would potentially increase salmon production, but there are also some concerns like increased hybridization of salmon and trout which is already evident downriver and which previous work suggests will increase as salmon colonize new habitat, and potential changes in fishing regulations as salmon distributions shift upriver and away from traditional angling areas. Here, we present an overview of ecological and social aspects of salmon habitat restoration in the River Nalon-Narcea that we hope will provide solutions that balance costs and benefits and may be applicable to other anadromous populations.

DNA analyses using four restriction enzymes (AvaIl, EcoRI, BamHI and XbaI) have been carried out to evaluate stocking success and to assess the amount and distribution of genetic variation among different populations of Spanish brown trout collected in rivers flowing to the Mediterranean and Cantabrian seas, and to the Atlantic Ocean. The hatchery stock was conspicuously different from the wild populations. mtDNA variation provided useful genetic markers to evaluate the success of stocking procedures in Spanish rivers. A relationship was found between population size and mtDNA variation. Between-population haplotype differences found in this work support the hypothesis of a recent divergence of all the Spanish brown trout from a common ancestral genotype.

We report a practical class designed for undergraduate students of Marine Sciences as a part of the Genetics course. The class can also be included in undergraduate studies of food technology. The exercise was designed to emphasize the application of molecular biology techniques to fish species authentication and traceability. After a simple and rapid protocol for DNA extraction, PCR was used to analyze variation in size of individual 5S ribosomal gene spacer sequences in eight commercially important fishes. The resulting fragments containing these sequences were separated on agarose gels and visualized under a UV lamp. Differences in fragment length can be used to differentiate between species. This method is particularly useful in the identification of larvae, eggs, and processed food including frozen and canned products.

. Genetic identification of hake and megrim eggs in formaldehyde-fixed plankton samples. e ICES Journal of Marine Science, 62: 908e914. Spawning of European hake (Merluccius merluccius) and megrim (Lepidorhombus whiffiagonis and L. boscii) overlap in time and space. Their eggs are morphologically similar, so genetic identification is needed for purposes of stock assessment based on plankton surveys. Amplification fragment sizes of a partial sequence within the 16S rRNA genes are different for Merluccius merluccius, Lepidorhombus boscii, and L. whiffiagonis. Species-specificity of the pattern was confirmed after analysing adult individuals from all distribution areas of the three species. After Chelex-based DNA extraction and PCR amplification, fragment sizes at this gene were successfully determined from 85% formaldehyde-fixed eggs and larvae recovered from plankton samples. Species-specificity was resolved using an ABI genetic analyser. The results were 100% reproducible. This methodology for genetic identification of hake and megrim eggs can be very useful for stock assessment of these three commercially important fish species.

DNA analyses using four restriction enzymes (AvaIl, EcoRI, BamHI and XbaI) have been carried out to evaluate stocking success and to assess the amount and distribution of genetic variation among different populations of Spanish brown trout collected in rivers flowing to the Mediterranean and Cantabrian seas, and to the Atlantic Ocean. The hatchery stock was conspicuously different from the wild populations. mtDNA variation provided useful genetic markers to evaluate the success of stocking procedures in Spanish rivers. A relationship was found between population size and mtDNA variation. Between-population haplotype differences found in this work support the hypothesis of a recent divergence of all the Spanish brown trout from a common ancestral genotype.

Atlantic salmon fry from nine offspring belonging to individual spawnings were karyotyped. Different patterns of Robertsonian chromosome polymorphism were obtained. A theoretical model is developed to explain the different chromosome polymorphism patterns in Salmo salar offspring in terms of the chromosome numbers of the parents.

Two stocks of brown trout employed in repopulating the rivers of Asturias (northern Spain) were morphologically and karyotypically analysed. Both stocks were significantly different. The foreign stock was less adequate for repopulation than the autochthonous stock.

We report a practical class designed for undergraduate students of Marine Sciences as a part of the Genetics course. The class can also be included in undergraduate studies of food technology. The exercise was designed to emphasize the application of molecular biology techniques to fish species authentication and traceability. After a simple and rapid protocol for DNA extraction, PCR was used to analyze variation in size of individual 5S ribosomal gene spacer sequences in eight commercially important fishes. The resulting fragments containing these sequences were separated on agarose gels and visualized under a UV lamp. Differences in fragment length can be used to differentiate between species. This method is particularly useful in the identification of larvae, eggs, and processed food including frozen and canned products.

. Genetic identification of hake and megrim eggs in formaldehyde-fixed plankton samples. e ICES Journal of Marine Science, 62: 908e914. Spawning of European hake (Merluccius merluccius) and megrim (Lepidorhombus whiffiagonis and L. boscii) overlap in time and space. Their eggs are morphologically similar, so genetic identification is needed for purposes of stock assessment based on plankton surveys. Amplification fragment sizes of a partial sequence within the 16S rRNA genes are different for Merluccius merluccius, Lepidorhombus boscii, and L. whiffiagonis. Species-specificity of the pattern was confirmed after analysing adult individuals from all distribution areas of the three species. After Chelex-based DNA extraction and PCR amplification, fragment sizes at this gene were successfully determined from 85% formaldehyde-fixed eggs and larvae recovered from plankton samples. Species-specificity was resolved using an ABI genetic analyser. The results were 100% reproducible. This methodology for genetic identification of hake and megrim eggs can be very useful for stock assessment of these three commercially important fish species.

Mussels Mytilus edulis were sampled at increasing distances from urban effluents in two very different locations, Gijon (northern Spain, Europe, 431N) and Puerto Madryn (Argentina, South America, 431S), and from an industry effluent in Puerto Madryn. The micronucleus test was performed on branchial cells. For the three situations, a statistically significant negative association was found between the distance of sampling site from the effluent and the mean number of micronuclei per 1000 cell counts, in a range of distances as short as 300 m. The micronucleus test in Mytilidae, here revealed to be sensitive enough to monitor urban pollution, is proposed for routine surveys of pollution as a bioindicator of choice for coastal ecosystems. r

Atlantic salmon fry from nine offspring belonging to individual spawnings were karyotyped. Different patterns of Robertsonian chromosome polymorphism were obtained. A theoretical model is developed to explain the different chromosome polymorphism patterns in Salmo salar offspring in terms of the chromosome numbers of the parents.

Two stocks of brown trout employed in repopulating the rivers of Asturias (northern Spain) were morphologically and karyotypically analysed. Both stocks were significantly different. The foreign stock was less adequate for repopulation than the autochthonous stock.

Two brown trout Salmo trutta stocks of different origin (wild Polish, domestic commercial) came into secondary contact after deliberate releases conducted in virgin rivers systems of the Subantarctic Kerguelen Islands (70° E 49° S). Samples obtained in 2001–2003 and a historical sample from 1993 were analysed for genetic variation at seven microsatellite loci and one allozyme locus (LDH-C1*). Bayesian clustering analysis demonstrated that rapid genetic differentiation formed separate genetic units in neighbouring rivers in less than 20 years. These genetic units were characterized by a large proportion of Polish genotypes mixed with some genomes of domestic origin (up to 30%). A different colonization strategy of the naturalized stocks, likely related with differential performance, was identified as a cause of rapid population differentiation in this area.

Mussels Mytilus edulis were sampled at increasing distances from urban effluents in two very different locations, Gijon (northern Spain, Europe, 431N) and Puerto Madryn (Argentina, South America, 431S), and from an industry effluent in Puerto Madryn. The micronucleus test was performed on branchial cells. For the three situations, a statistically significant negative association was found between the distance of sampling site from the effluent and the mean number of micronuclei per 1000 cell counts, in a range of distances as short as 300 m. The micronucleus test in Mytilidae, here revealed to be sensitive enough to monitor urban pollution, is proposed for routine surveys of pollution as a bioindicator of choice for coastal ecosystems. r