Yeast cells are well adapted to interfacial habitats, such as the surfaces of soil or plants, where they can resist frequent fluctuations between wet and dry conditions. Saccharomyces cerevisiae is recognized as an anhydrobiotic organism, and it has been the subject of numerous studies that aimed to elucidate this ability. Extensive data have been obtained from these studies based on a wide range of experimental approaches, which have added significantly to our understanding of the cellular bases and mechanisms of resistance to desiccation. The aim of this review is to provide an integrated view of these mechanisms in yeast and to describe the survival kit of S. cerevisiae for anhydrobiosis. This kit comprises constitutive and inducible mechanisms that prevent cell damage during dehydration and rehydration. This review also aims to characterize clearly the phenomenon of anhydrobiosis itself based on detailed descriptions of the causes and effects of the constraints imposed on cells by desiccation. These constraints mainly lead to mechanical, structural, and oxidative damage to cell components. Considerations of these constraints and the possible utilization of components of the survival kit could help to improve the survival of sensitive cells of interest during desiccation.
Measures of microbial growth, used as indicators of cellular stress, are sometimes quantified at a single time-point. in reality, these measurements are compound representations of length of lag, exponential growth-rate, and other factors. Here, we investigate whether length of lag phase can act as a proxy for stress, using a number of model systems (Aspergillus penicillioides; Bacillus subtilis; Escherichia coli; Eurotium amstelodami, E. echinulatum, E. halophilicum, and e. repens; Mrakia frigida; Saccharomyces cerevisiae; Xerochrysium xerophilum; Xeromyces bisporus) exposed to mechanistically distinct types of cellular stress including low water activity, other solute-induced stresses, and dehydrationrehydration cycles. Lag phase was neither proportional to germination rate for X. bisporus (FRR3443) in glycerol-supplemented media (r 2 = 0.012), nor to exponential growth-rates for other microbes. In some cases, growth-rates varied greatly with stressor concentration even when lag remained constant. By contrast, there were strong correlations for B. subtilis in media supplemented with polyethyleneglycol 6000 or 600 (r 2 = 0.925 and 0.961), and for other microbial species. We also analysed data from independent studies of food-spoilage fungi under glycerol stress (Aspergillus aculeatinus and A. sclerotiicarbonarius); mesophilic/psychrotolerant bacteria under diverse, solute-induced stresses (Brochothrix thermosphacta, Enterococcus faecalis, Pseudomonas fluorescens, Salmonella typhimurium, Staphylococcus aureus); and fungal enzymes under acid-stress (Terfezia claveryi lipoxygenase and Agaricus bisporus tyrosinase). these datasets also exhibited diversity, with some strong-and moderate correlations between length of lag and exponential growth-rates; and sometimes none. in conclusion, lag phase is not a reliable measure of stress because length of lag and growth-rate inhibition are sometimes highly correlated, and sometimes not at all. Chemical reactions and thermodynamic and biological processes often experience a lag period prior to reaching their maximum rate. This phenomenon that can be observed at various levels; thermodynamic processes (e.g. thermal lag), chemical reactions, biochemical activities 1 , cellular physiology 2 , microbial growth kinetics, and ecosystem functions 3. The term lag, used in English since the early 14 th century, has been applied to biological processes since at least the 1680s 4. In the context of microbial growth kinetics, lag, once known as 'latency' , was studied since the 1800s, including work of Louis Pasteur 5. Despite this long pedigree of research into this phenomenon, however, some aspects of the biology and application of the lag phase are not yet resolved. Accurate assessments of microbial growth must account for the various growth processes, including: mycelial extension, cell division within planktonic populations, increases in the mass of individual cells, accumulation of compatible solutes or other endogenous reserves, cell elongation or growth, sporulation, germination,...
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