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

Abstract

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,...

Symbiosis between nanohaloarchaeon and haloarchaeon is based on utilization of different polysaccharides

“…In contrast, none of the low-molecular-weight chitodextrin oligomers, (GlcNAc) 2-6 , was detected. The presence of the ectosymbiont in a coculture slightly prolonged the growth lag phase of the host, a phenomenon that implies an adaptation period although not necessarily (biotic or abiotic) stress (38). Indeed, neither the maximum specific growth rates (0.028 to 0.035 h −1 ) nor the yield of the host biomass were affected (Fig.…”

Organic Nutrients Induced Coupled C- and P-Cycling Enzyme Activities During Microbial Growth in Forest Soils

“…By the addition of glucose + yeast extract, the lag phase of growing microorganisms shortened irrespective of the initial nutrient content (Table 2), reflecting an advanced adaptation to the newly available resources, fueling a balanced, and less stressed metabolic network (Hamill et al, 2020). However, the substrate turnover time of C-, N-, and P-cycling extracellular enzymes during lag phase and exponential growth of microorganisms was stable in nutrient-rich soil, whereas the substrate turnover time of enzymes was strongly shortened in nutrient-poor soil (Figure 8).…”

“…These growth curves show different phases of microbial growth, namely (1) lag, (2) exponential, (3) stationary and 4) death phase (Figure 1). In general, the lag phase metabolism may include the activation of signaling pathways and specific transcriptional changes which might lead to the upregulation of protein assembly, nucleotide metabolism, lipopolysaccharide biosynthesis, respiration, and other processes which are needed for differentiation and multiplication (Hamill et al, 2020). These processes occur during lag phase, initiate exponential growth and cell divisions (Panikov, 1991).…”

Long-Term Adaption to High Osmotic Stress as a Tool for Improving Enological Characteristics in Industrial Wine Yeast

“…After the end of the ALE experiment, we assessed an effect of 2M KCl-induced osmotic stress on the growth phenotype of the analyzed strains by using a spot test assay, which is a standard method to evaluate the growth phenotype [35][36][37]. We showed that KCl-evolved derivatives of strains 2 and 3 (2_KCl_a, 2_KCl_b as well as 3_KCl_a, and 3_KCl_b, respectively) significantly increased their fitness to high osmotic pressure.…”

“…In fact, there are several reports showing that the mRNAs of genes engaged in the stress response are regulated differently in comparison to other [50,51]. Examples include the upregulation of synthesis, the extension of the transcript half-lives [36], and finally selective mRNAs stabilization (or degradation) that, in turn, are dependent on the stress response phase [51].…”