Effects of the kinetics of water potential variation on bacteria viability

Poirier, Isabelle; Marechal, Pierre-André; Gervais, Patrick

doi:10.1111/j.1365-2672.1997.tb03303.x

Cited by 41 publications

(18 citation statements)

References 20 publications

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“…For example, the inactivation of MscS channels in patch clamp measurements can be observed only when the pressure is applied gradually (7) over tens of seconds. Finally, there are studies that demonstrate that cell survival depends on the time scale over which the external water potential is changed (10)(11)(12). However, to our knowledge, no work has analyzed how the presence or absence of various MS channels impacts cell survival under time-dependent conditions.…”

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confidence: 99%

The Rate of Osmotic Downshock Determines the Survival Probability of Bacterial Mechanosensitive Channel Mutants

2015

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Mechanosensitive (MS) channels allow cells to sense and respond to environmental changes. In bacteria, these channels are believed to protect against an osmotic shock. The physiological function of these channels has been characterized primarily by a standardized assay, where aliquots of batch-cultured cells are rapidly pipetted into a hypotonic medium. Under this method, it has been inferred many types of MS channels (MscS homologs in Escherichia coli) demonstrate limited effectiveness against shock, typically rescuing less than 10% of the cells when expressed at native levels. We introduce a single-cell-based assay which allows us to control how fast the osmolarity changes, over time scales ranging from a fraction of a second to several minutes. We find that the protection provided by MS channels depends strongly on the rate of osmotic change, revealing that, under a slow enough osmotic drop, MscS homologs can lead to survival rates comparable to those found in wild-type strains. Further, after the osmotic downshift, we observe multiple death phenotypes, which are inconsistent with the prevailing paradigm of how cells lyse. Both of these findings require a reevaluation of our basic understanding of the physiology of MS channels. Mechanosensation is a ubiquitous phenomenon found across all domains of life. In bacteria, one of the manifestations of such processes is in the context of osmoprotection, where it has been proposed that the presence of mechanosensitive (MS) channels in the cell membrane allows these cells to survive immersion into hypotonic environments. These channels gate in response to an increase in membrane tension and prevent membrane rupture by mediating net flux of water and small molecules. The first bacterial mechanosensitive channels were discovered in 1987 (1), and in the intervening period several more channels have been discovered. For example, seven different types (MscL and 6 MscS homologs) have been demonstrated in Escherichia coli (2). More generally, the trend of having multiple MscS homologs seems to occur in many other bacterial species as well (3, 4). One of the puzzles left unresolved in the wake of the discovery of this mechanosensitive protein diversity is why there are so many distinct mechanosensitive channels and the nature of their significance for cell physiology. Perhaps cues can be taken from examining the cell's native environment, but at present, it is not known (at least to the authors) which environmental factors are crucial.The physiology of MS channels has been studied extensively over the past 20 years. Specifically, until now, the in vivo function of these channels has been characterized mainly by "hypo-osmotic challenge" assays, where an aliquot from batch culture is suddenly diluted into a lower-osmolarity medium, typically by hand pipetting. The resulting survival fraction is inferred several hours after the shock by counting colonies of plated dilutions or monitoring the optical density from the resulting mixture. The comparison of the batch survival rate fo...

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confidence: 99%

The Rate of Osmotic Downshock Determines the Survival Probability of Bacterial Mechanosensitive Channel Mutants

2015

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“…For example, survival of Salmonella may be greater when dehydration is gradual. 39 Poirier et al 40 showed that decreasing the rate of change in water potential increased the viability of several bacterial cells likely due to associated reductions in water flow rates across cell membranes. 40 Down-or upregulation of biological processes, such as metabolic rates, DNA repair capabilities, or systems to scavenge reactive oxygen species, during slow dehydration can influence bacterial survival.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…39 Poirier et al 40 showed that decreasing the rate of change in water potential increased the viability of several bacterial cells likely due to associated reductions in water flow rates across cell membranes. 40 Down-or upregulation of biological processes, such as metabolic rates, DNA repair capabilities, or systems to scavenge reactive oxygen species, during slow dehydration can influence bacterial survival. 37,41 However, high relative humidity can also lead to more efficient inactivation of dehydration tolerant bacteria, as shown for Deinococcus radiodurans cells.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Bacteria Inactivation during the Drying of Struvite Fertilizers Produced from Stored Urine

Bischel

Schindelholz

Schoger

et al. 2016

Environ. Sci. Technol.

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Human urine can be processed into market-attractive fertilizers like struvite; however, concerns regarding the microbial safety of such products remain. The present study evaluated the inactivation of in situ heterotrophs, total bacteria as observed by flow cytometry, and inoculated Enterococcus spp. and Salmonella typhimurium during the drying of struvite under controlled temperature (from 5 to 35°C) and relative humidity (approximately 40 and 80%) as well as dynamic field conditions. Bacteria accumulated in the struvite cake during struvite filtration. Despite the use of sublethal temperatures, all bacteria types were subsequently inactivated to some degree during struvite drying, and the inactivation typically increased with increasing drying temperature for a given relative humidity. Heterotrophic bacteria inactivation mirrored the trend in total bacteria during struvite drying. A linear relationship was observed between inactivation and sample moisture content. However, bacteria survivor curves were typically nonlinear when struvite was dried at low relative humidity, indicating bacterial persistence. Weibull model survivor curve fits indicated that a shift in the mechanism of inactivation may occur with changing humidity. For increased efficiency of bacterial inactivation during the production of struvite, initial heating under moist conditions is recommended followed by desiccation.

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“…La mesure de la viabilité cellulaire est réa-lisée par la méthode UFC, comme décrit par Poirier et al [8]. …”

Section: Mesure De La Viabilité Cellulaireunclassified

“…L'existence de ces cinétiques optimales peut être expliquée par l'opposition de deux actions sur la viabilité cellulaire. Premièrement, une action positive qui est la diminution lente du potentiel hydrique et deuxièmement, une action négative qui est le temps de résidence des cellules dans une zone critique de potentiel hydrique [8].…”

Section: éTude De Conservation Des éChantillons Déshydratésunclassified

Survie des bactéries lactiques soumises à la déshydratation : importance de la cinétique de déshydratation

Poirier

Marechal

Gervais

1998

Lait

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Abstract-Viability of lactic bacteria submitted to dehydration: Importance of the dehydration kinetics. Dehydration of Lactobacillus plantarum by glycerol addition (water depressor) has allowed to show the great importance of the kinetics of water potential decrease on cell viability. Thus, wathever the final water potential was, an optimal kinetics of water potential variation was detennined which allow to maintain a viability higher than 80%. Decreasing rate and level of water potential have been proved to influence cell viability in the same way during air drying at 25 oc. In this case, optimal kinetics of dehydration preserved 40% of viable cells. This viabilit Y was higher than 80% when a nutritional stress was realised before dehydration and when cells were rehydrated at 37 oc. A high preservation of dehydrated cells was observed for 3 months at -317.9 MPa (~= 0.100); and after rehydration, stressed cells exhibited an acid production similar to a control. © Inra/Elsevier, Paris. Lactobacillus plantarum

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Effects of the kinetics of water potential variation on bacteria viability

Cited by 41 publications

References 20 publications

The Rate of Osmotic Downshock Determines the Survival Probability of Bacterial Mechanosensitive Channel Mutants

The Rate of Osmotic Downshock Determines the Survival Probability of Bacterial Mechanosensitive Channel Mutants

Bacteria Inactivation during the Drying of Struvite Fertilizers Produced from Stored Urine

Survie des bactéries lactiques soumises à la déshydratation : importance de la cinétique de déshydratation

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