Microbial water stress.

Brown, A. D.

doi:10.1128/mmbr.40.4.803-846.1976

Cited by 517 publications

(260 citation statements)

References 82 publications

(153 reference statements)

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“…1A) which indicate considerable breadth of temperature and water-activity tolerance, with a theoretical water-activity minimum for growth of < 0.877 at 37°C (derived by regression analysis as described in Experimental procedures; r 2 = 1). 2 By 1 Glycerol at low concentrations acts as an effective compatible solute (Brown, 1976;Hallsworth et al, 2003a;Bhaganna et al, 2010); at high concentrations, of > 4 M, can act as a chaotropic stressor at temperatures above 10°C Chin et al, 2010); and at intermediate concentrations such as those used in the current study (1-4 M) primarily acts as a biologically permissive solute for fungal or bacterial cells which reduces water activity (see also Hallsworth et al, 1998;Cray et al, 2013b). 2 The construction of isopleth profiles indicated a theoretical wateractivity limit close to 0.871 aw between 34.5°C and 36°C (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Throughout the past 50 years of microbiological research, the established water-activity windows for cell division of xerophiles have remained unchanged (Pitt and Christian, 1968;Brown, 1976;1990;Grant, 2004;Stevenson et al, 2014) despite the recent interest in habitability of hostile environments in relation to searches for life beyond the Earth (Marion and Kargel, 2008;Kminek et al, 2010;Harrison et al, 2013;Stevenson et al, 2014 . For any data that can provide definitive evidence for microbial cell division at water activities significantly below 0.605, the potential implications would be manifold.…”

Section: Water-activity Limits For Soil-dwelling Actinobacteria and Cmentioning

confidence: 99%

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Water and temperature relations of soil Actinobacteria

Stevenson

Hallsworth

2014

Environ Microbiol Rep

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Actinobacteria perform essential functions within soils, and are dependent on available water to do so. We determined the water-activity (aw ) limits for cell division of Streptomyces albidoflavus, Streptomyces rectiviolaceus, Micromonospora grisea and Micromonospora (JCM 3050) over a range of temperatures, using culture media supplemented with a biologically permissive solute (glycerol). Each species grew optimally at 0.998 aw (control; no added glycerol) and growth rates were near-optimal in the range 0.971-0.974 (1 M glycerol) at permissive temperatures. Each was capable of cell division at 0.916-0.924 aw (2 M glycerol), but only S. albidoflavus grew at 0.895 or 0.897 aw (3 M glycerol, at 30 and 37°C respectively). For S. albidoflavus, however, no growth occurred on media at ≤ 0.870 (4 M glycerol) during the 40-day assessment period, regardless of temperature, and a theoretical limit of 0.877 aw was derived by extrapolation of growth curves. This level of solute tolerance is high for non-halophilic bacteria, but is consistent with reported limits for the growth and metabolic activities of soil microbes. The limit, within the range 0.895-0.870 aw , is very much inferior to those for obligately halophilic bacteria and extremely halophilic or xerophilic fungi, and is inconsistent with earlier reports of cell division at 0.500 aw . These findings are discussed in relation to planetary protection policy for space exploration and the microbiology of arid soils.

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Section: Resultsmentioning

confidence: 99%

Section: Water-activity Limits For Soil-dwelling Actinobacteria and Cmentioning

confidence: 99%

Water and temperature relations of soil Actinobacteria

Stevenson

Hallsworth

2014

Environ Microbiol Rep

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“…Furthermore, systematic studies of water-activity limits for cell division of phylogenetically diverse extremotolerant and extremophilic microbes 10 suggest that cell division would be implausible at values much below 0.600 aw (i.e. 60% equilibrium relative humidity) (Pitt and Christian, 1968;Brown, 1976;…”

Section: Microbial Cell Division Via Utilization Of Water Which Is Nomentioning

confidence: 99%

Multiplication of microbes below 0.690 water activity: implications for terrestrial and extraterrestrial life

Stevenson

Burkhardt

Cockell

et al. 2014

Environmental Microbiology

154

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SummarySince a key requirement of known life forms is available water (water activity; a w), recent searches for signatures of past life in terrestrial and extraterrestrial environments have targeted places known to have contained significant quantities of biologically available water. However, early life on Earth inhabited high-salt environments, suggesting an ability to withstand low water-activity. The lower limit of water activity that enables cell division appears to be ∼ 0.605 which, until now, was only known to be exhibited by a single eukaryote, the sugar-tolerant, fungal xerophile Xeromyces bisporus. The first forms of life on Earth were, though, prokaryotic. Recent evidence now indicates that some halophilic Archaea and Bacteria have water-activity limits more or less equal to those of X. bisporus. We discuss water activity in relation to the limits of Earth's present-day biosphere; the possibility of microbial multiplication by utilizing water from thin, aqueous films or non-liquid sources; whether prokaryotes were the first organisms able to multiply close to the 0.605-a w limit; and whether extraterrestrial aqueous milieux of ≥ 0.605 aw can resemble fertile microbial habitats found on Earth.

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“…Many bacteria adapt to increased osmolarity by importing or producing compatible solutes to counteract osmotic pressure (Wood, 1999). Compatible solutes are small, highly soluble organic molecules that act to stabilize intracellular levels of water and turgor pressure without disturbing cellular function (Brown, 1976). Compatible solutes can be divided into various groups including carbohydrates, polyols, heterosides, amino acids and amino acid derivatives (da Costa et al, 1998;Sleator and Hill, 2002).…”

Section: Introductionmentioning

confidence: 99%

The transcriptional regulator, CosR, controls compatible solute biosynthesis and transport, motility and biofilm formation in Vibrio cholerae

Shikuma

Davis

Fong

et al. 2012

Environmental Microbiology

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Summary Vibrio cholerae inhabits aquatic environments and colonizes the human digestive tract to cause the disease cholera. In these environments, V. cholerae copes with fluctuations in salinity and osmolarity by producing and transporting small, organic, highly soluble molecules called compatible solutes, which counteract extracellular osmotic pressure. Currently, it is unclear how V. cholerae regulates the expression of genes important for the biosynthesis or transport of compatible solutes in response to changing salinity or osmolarity conditions. Through a genome‐wide transcriptional analysis of the salinity response of V. cholerae, we identified a transcriptional regulator we name CosR for compatible solute regulator. The expression of cosR is regulated by ionic strength and not osmolarity. A transcriptome analysis of a ΔcosR mutant revealed that CosR represses genes involved in ectoine biosynthesis and compatible solute transport in a salinity‐dependent manner. When grown in salinities similar to estuarine environments, CosR activates biofilm formation and represses motility independently of its function as an ectoine regulator. This is the first study to characterize a compatible solute regulator in V. cholerae and couples the regulation of osmotic tolerance with biofilm formation and motility.

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Microbial water stress.

Abstract: being used to denote an ideal solvent), R is the universal gas constant, T the absolute temperature, fj the number of moles of species j, V,, the partial molal volume of the solvent (water), and n,, is the number of moles of water.

Cited by 517 publications

References 82 publications

Water and temperature relations of soil Actinobacteria

Water and temperature relations of soil Actinobacteria

Multiplication of microbes below 0.690 water activity: implications for terrestrial and extraterrestrial life

The transcriptional regulator, CosR, controls compatible solute biosynthesis and transport, motility and biofilm formation in Vibrio cholerae

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