On microbial states of growth†

Acta scientific microbiology, 2024

Antonie van Leeuwenhoek, 1993

Growth is the expression par excellence of the dynamic nature of living organisms. Among the general methods available for the scientific investigation of dynamic phenomena, the most useful ones are those that deal with kinetic aspects. Kinetic investigations on cultures of microorganisms are eminently suited for establishing relationships between growth and environmental factors, especially the nature and amount of nutrients. C.B. van Niel (1949) The study of the growth of bacterial cultures does not constitute a specialised subject of branch of research: it is the basic method of Microbiology. Monod (1949)

Microbiological Quality Assurance, 2018

INTRODUCTION Upon depletion of essential nutrients from the medium, the growth rate of a bacterial culture slows down and evenually reaches zero. At this point the culture has entered stationary phase. The term "stationary phase" should be understood as an operational term indicating that the culture is displaying no net increase in cell number. However, the physiology of cells in a stationary-phase culture is heterogeneous and depends completely on the conditions that resulted in the cessation of growth. Starvation for an essential nutrient, perhaps most often the carbon source, has been used experimentally as a tool to study the physiology of nongrowing cells. Changes resulting from carbon source starvation, however, should not be assumed to hold for other forms of entry into stationary phase. When the term stationary phase is used here, the reader should keep in mind that the observation described may only apply for the particular conditions used in each experiment and that generalizations may not be valid. The transition from rapid growth with a generation time of less than 20 min to stationary phase is accompanied by adaptation of the culture to the new conditions. During growth, energy-demanding processes convert nutrients primarily to nucleic acids, proteins, and other cell constituents to enable cell growth and cell division. Rapidly growing cells rely on inducible responses to express defense mechanisms against particular stress conditions. In stationary phase, energy generation is usually limited (79), making inducible responses less immediate and less effective. It thus makes sense for organisms such as Escherichia coli and Salmonella typhimurium (Salmonella enterica serovar Typhimurium) to develop increased resistances against many potential environmental assaults at the onset of starvation. Such a program is advantageous to the cell because it can cope with environmental stresses instantaneously without requiring new protein synthesis. In this way, precious energy equivalents are preserved and chances for survival are not impaired. A possible consequence of the development of a highly resistant state is that resumption of growth may take more time since the protective measures have to be dismantled. Within a population, cells that have not fully expressed their increased resistances might respond more quickly to conditions supporting growth and could have an advantage in resuming growth. The identification of mutants that take over stationaryphase cultures supports this possibility (178). One potential result is that a culture that is repeatedly switched from starvation to growth conditions loses its clonal identity and evolves into a mixture of cell genotypes. Some conditions appear to select mutants that can take over the population (178), while other conditions select for balanced mixtures of cells that complement each other (135). The observations that starved cultures can quickly lose their clonality should undoubtedly warn workers in this field to exercise extreme care when storing bacterial strains in agar stabs and plates. This chapter describes the changes that E. coli and S. typhimurium undergo when starved. We summarize the changes (schematically represented in Fig. 1) that occur in the different subcellular compartments and in the genome and describe genes that have been found to be essential to survive in stationary phase. Several additional reviews describing bacteria in stationary phase and gene expression in slowly growing cells have appeared recently (65, 72, 81, 101, 102, 145).

Frontiers in Microbiology, 2015

Virtually every microbiological experiment starts with the cultivation of microbes. Consequently, as originally pointed out by Monod (1949), handling microbial cultures is a fundamental methodology of microbiology and mastering different cultivation techniques should be part of every microbiologist's craftsmanship. This is particularly important for research in microbial physiology, as the composition and behavior of microbes is strongly dependent on their growth environment. It has been pointed out repeatedly by eminent microbiologists that we should give more attention to the media and culturing conditions. However, this is obviously not adhered to with sufficient rigor as mistakes in basic cultivation principles are frequently found in the published research literature. The most frequent mistakes are the use of inappropriate growth media and little or no control of the specific growth rate, and some examples will be discussed here in detail. Therefore, this is a call for better microbiological craftsmanship when cultivating microbial cultures for physiological experiments. This call is not only addressed to researchers but it is probably even more important for the teaching of our discipline.

Cells

The growth of bacterial populations has been described as a dynamic process of continuous reproduction and cell death. However, this is far from the reality. In a well fed, growing bacterial population, the stationary phase inevitably occurs, and it is not due to accumulated toxins or cell death. A population spends the most time in the stationary phase, where the phenotype of the cells alters from the proliferating ones, and only the colony forming unit (CFU) decreases after a while, not the total cell concentration. A bacterial population can be considered as a virtual tissue as a result of a specific differentiation process, in which the exponential-phase cells develop to stationary-phase cells and eventually reach the unculturable form. The richness of the nutrient had no effect on growth rate or on stationary cell density. The generation time seems not to be a constant value, but it depended on the concentration of the starter cultures. Inoculations with serial dilutions of sta...

Biochimica Et Biophysica Acta, 1982

Biotechnology and Bioengineering, 1976

One of the main criticisms to the current chemostat theory is that it uses a first order rate expression to describe the microbial growth taking place in the vessel. This rate equation is

Journal of bacteriology, 1982

The Arrhenius Law, which was originally proposed to describe the temperature dependence of the specific reaction rate constant in chemical reactions, does not adequately describe the effect of temperature on bacterial growth. Microbiologists have attempted to apply a modified version of this law to bacterial growth by replacing the reaction rate constant by the growth rate constant, but the modified law relationship fits data poorly, as graphs of the logarithm of the growth rate constant against reciprocal absolute temperature result in curves rather than straight lines. Instead, a linear relationship between in square root of growth rate constant (r) and temperature (T), namely, square root = b (T - T0), where b is the regression coefficient and T0 is a hypothetical temperature which is an intrinsic property of the organism, is proposed and found to apply to the growth of a wide range of bacteria. The relationship is also applicable to nucleotide breakdown and to the growth of yeas...

FEMS Microbiology Letters, 1982