Microbial lag phase can be indicative of, or independent from, cellular stress

Microbial lag phase can be indicative of, or independent from, cellular stress

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...

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Published in:Scientific reports Vol. 10; no. 1; p. 5948
Main Authors: Hamill, Philip G., Stevenson, Andrew, McMullan, Phillip E., Williams, James P., Lewis, Abiann D. R., S, Sudharsan, Stevenson, Kath E., Farnsworth, Keith D., Khroustalyova, Galina, Takemoto, Jon Y., Quinn, John P., Rapoport, Alexander, Hallsworth, John E.
Format: Journal Article
Language:English
Published: London Nature Publishing Group UK 03-04-2020
Nature Publishing Group
Subjects:
631/326
631/61
Aspergillus
Aspergillus - physiology
Bacillus subtilis - physiology
Cell Growth Processes - physiology
Cell Survival
Culture Media
Dehydration
E coli
Escherichia coli - physiology
Food spoilage
Fungi
Germination
Glycerol
Humanities and Social Sciences
Lag phase
Lipoxygenase
multidisciplinary
Polyethylene glycol
Rehydration
Science
Science (multidisciplinary)
Stress, Physiological - physiology
Temperature
Water activity
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Summary: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 dehydration-rehydration 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 polyethylene-glycol 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. sclerotiicarbonariu s); 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.
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ISSN:2045-2322
2045-2322
DOI:10.1038/s41598-020-62552-4