Ethanol-induced water stress and fungal growth

Hallsworth, John E.; Nomura, Yasuya; Iwahara, M.

doi:10.1016/s0922-338x(98)80150-5

Cited by 64 publications

(46 citation statements)

References 20 publications

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“…These results are consistent with the hypothesis that compatible solutes are general protective agents against different forms of water stress and extend our previous observations that microbial growth and metabolism are inhibited by chaotropeinduced water stress (11,12,14). These results also raise the question of whether the principal stress mediated by both chaotropic and kosmotropic solutes is the same, namely, a perturbation of water-macromolecule relations.…”

Section: Discussionsupporting

confidence: 91%

Compatible Solutes Protect against Chaotrope(Ethanol)-Induced, Nonosmotic WaterStress

Hallsworth

Prior

Nomura

et al. 2003

Appl Environ Microbiol

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Water stress is one of the major stresses experienced by cellular systems and can take a number of distinct forms. In response to turgor-related osmotic stress, cells produce compatible solutes that are macromolecule protectants and also counteract the outflow of water from stressed cells. In this report we show that the germination of conidia of Aspergillus nidulans, a sensitive indicator of water stress, in the presence of ethanol is correlated with the intracellular concentration of the compatible solutes glycerol and erythritol, which protect against both osmotic and nonturgor forms of water stress.Cellular systems consist of up to 97% water, so thermodynamic changes in water availability cause fundamental biological stress that can severely impact vital metabolic processes (3). Water stress can be induced by a net loss of water from cells, e.g., due to high levels of extracellular solutes such as NaCl that reduce cell turgor and induce osmotic stress. Cells exposed to such agents are subjected to both reduced turgor and stabilizing effects on macromolecules, which can lead to membrane rigidity and impairment of protein structure (3,16,19,25). Intracellular water activity also may be reduced by chaotropic compounds, such as ethanol, that decrease the strength of hydrogen bonding and other electrostatic interactions and thereby perturb the structure and function of hydrated macromolecules, including nucleic acids, proteins, and lipids.Cells generally respond to osmotic stress by acquiring and/or producing compatible solutes that protect macromolecule structure and at the same time increase the osmotic pressure of the cytoplasm and thereby counteract water loss from cells (1, 3). Our working hypothesis is that these compatible solutes also protect against intracellular water stress due to alterations in the hydration of cellular macromolecules caused by ethanol, a chaotropic solute that does not cause osmotic stress.The ascomycete Aspergillus (Emericella) nidulans is a model microorganism whose genetics and metabolism, including those related to stress and toxicology, have been widely studied. A. nidulans, like most yeast and fungal cells, synthesizes low-molecular-weight polyols, such as glycerol, in response to osmotic stress (3, 21). Our objective in this study was to determine whether increased intracellular levels of glycerol and erythritol affect conidial germination in A. nidulans when the organism is cultured under conditions that reduce cell turgor and induce osmotic stress (e.g., in a high-NaCl environment), as well as those that increase intracellular water stress by reducing the strength of water-macromolecule interactions (e.g., at high ethanol concentrations). MATERIALS AND METHODSOrganism, media, and production of conidia. A culture of A. nidulans (IFO 4342) was obtained from the Institute for Fermentation Osaka (Osaka, Japan) and maintained on potato dextrose agar (PDA; Nissui, Tokyo, Japan) at 25°C. All media were buffered with 21.3 g of 2-(N-morpholino)ethanesulfonic acid (MES) liter Ϫ1 , and...

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Section: Discussionsupporting

confidence: 91%

Compatible Solutes Protect against Chaotrope(Ethanol)-Induced, Nonosmotic WaterStress

Hallsworth

Prior

Nomura

et al. 2003

Appl Environ Microbiol

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“…A range of taxonomically diverse extremophilic microbes were screened for stress tolerance on solute-supplemented nutrient media (10,46) over a range of temperatures; these included algae, fungi and yeasts, bacteria and Archaea (SI Materials and Methods). Water-activity values were quantified using a Novasina IC-II water-activity machine fitted with an alcohol-resistant humidity sensor and eVALC alcohol filter (Novasina), as described previously (47).…”

Section: Methodsmentioning

confidence: 99%

Solutes determine the temperature windows for microbial survival and growth

Chin¹,

Megaw²,

Magill³

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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138

185

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Microbial cells, and ultimately the Earth's biosphere, function within a narrow range of physicochemical conditions. For the majority of ecosystems, productivity is cold-limited, and it is microbes that represent the failure point. This study was carried out to determine if naturally occurring solutes can extend the temperature windows for activity of microorganisms. We found that substances known to disorder cellular macromolecules (chaotropes) did expand microbial growth windows, fungi preferentially accumulated chaotropic metabolites at low temperature, and chemical activities of solutes determined microbial survival at extremes of temperature as well as pressure. This information can enhance the precision of models used to predict if extraterrestrial and other hostile environments are able to support life; furthermore, chaotropes may be used to extend the growth windows for key microbes, such as saprotrophs, in cold ecosystems and manmade biomes.

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“…The inhibition of fungal growth was partly attributed to the decrease of a w due to ethanol. Water stress accounted for up to 31, 18 and 6% of growth inhibition of A. oryzae by ethanol at 25, 40, and 42.5 C respectively (Hallsworth, Nomura, & Iwahara, 1998).…”

Section: Mode Of Action Of Ethanol On Fungimentioning

confidence: 98%