Natural-abundance 13C Nuclear Magnetic Resonance Studies on the Internal Solutes of Xerophilic Fungi

Hocking, Ailsa D.; Norton, Raymond S.

doi:10.1099/00221287-129-9-2915

Cited by 30 publications

(33 citation statements)

References 25 publications

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“…Our results, which indicate an inverse correlation between the molecular weight of polyol and the proportion lost, are consistent with changes in permeability. In some procedures using liquid culture (9,12), washing has been avoided altogether, but such a strategy is only appropriate when the solutes being measured are either absent or present at only low concentrations in the external medium. Another approach has been to grow mycelium on cellophane overlaying solid media and to harvest without washing (12,18).…”

Section: Resultsmentioning

confidence: 99%

“…In some procedures using liquid culture (9,12), washing has been avoided altogether, but such a strategy is only appropriate when the solutes being measured are either absent or present at only low concentrations in the external medium. Another approach has been to grow mycelium on cellophane overlaying solid media and to harvest without washing (12,18). However, the proportion of solute that was present in the cell wall and periplasmic space external to the plasma membrane was not estimated in these studies.…”

Section: Resultsmentioning

confidence: 99%

“…Because the mode of action of the dicarboximides, which include iprodione, procymidone, and vinclozolin, is not yet known (4), it was anticipated that an understanding of how these fungi adapt to osmotic stress would aid studies of their mode of action. Little data are available on osmotic adaptation in the ascomycetous fungi, although recent studies implicate glycerol as the major osmoregulator in this group (9,12,18,19). In this study, we report on osmotic adaptation in a wild-type strain of the fungus Aspergillus nidulans.…”

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Osmotic adjustment in the filamentous fungus Aspergillus nidulans

Beever¹,

Laracy²

1986

J Bacteriol

110

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Aspergillus nidulans was shown to be xerotolerant, with optimal radial growth on basal medium amended with 0.5 M NaCl (osmotic potential [*,] of medium, -3 MPa), 50% optimal growth on medium amended with 1.6 M NaCl (*s of medium, -8.7 MPa), and little growth on medium amended with 3.4 M NaCl (*, of medium, -21 MPa). The intracellular content of soluble carbohydrates and of selected cations was measured after growth on basal medium, on this medium osmotically amended with NaCl, KCI, glucose, or glycerol, and also after hyperosmotic and hypoosmotic transfer. The results implicate glycerol and erythritol as the major osmoregulatory solutes. They both accumulated during growth on osmotically amended media, as well as after hyperosmotic transfer, except on glycerol-amended media, in which erythritol did not accumulate. Furthermore, they both decreased in amount after hypoosmotic transfer. With the exception of glycerol, the extracellular osmotic solute did not accumulate intracellularly when mycelium was grown in osmotically amended media, but it accumulated after hyperosmotic transfer. It was concluded that the extracellular solute usually plays only a transient role in osmotic adaptation. The intracellular content of soluble carbohydrates and cations measured could reasonably account for the intracellular osmotic potential of mycelium growing on osmotically amended media.The ability of microorganisms to grow under conditions of low osmotic (solute) potential has received considerable attention (5, 6, 10). For microorganisms with a cell wall, it is accepted that for active growth the internal water potential must be slightly lower than that external to the cell, so that water will tend to flow into the cell and generate the turgor potential needed for growth. For such microorganisms to grow under conditions of low osmotic potential, this low internal potential is generated largely by the intracellular accumulation of one or more low-molecular-weight solutes or osmoregulators. Although any solute will contribute to the water potential, only a restricted group, the so-called compatible solutes, can accumulate to high concentrations without interfering with enzyme activity and intracellular metabolism.We became interested in the mechanisms whereby ascomycetous filamentous fungi adapt to osmotic stress after we found, with three species, that most mutants resistant to the dicarboximide group of agricultural fungicides are abnormally sensitive to low osmotic potential (3). Because the mode of action of the dicarboximides, which include iprodione, procymidone, and vinclozolin, is not yet known (4), it was anticipated that an understanding of how these fungi adapt to osmotic stress would aid studies of their mode of action. Little data are available on osmotic adaptation in the ascomycetous fungi, although recent studies implicate glycerol as the major osmoregulator in this group (9,12,18,19). In this study, we report on osmotic adaptation in a wild-type strain of the fungus Aspergillus nidulans. MATERIALS AND METHODSOrgan...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Osmotic adjustment in the filamentous fungus Aspergillus nidulans

Beever¹,

Laracy²

1986

J Bacteriol

110

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“…Glycerol was the major osmotically active solute found in the eight yeast species studied here as well as a total of 18 species investigated by , Reed et al (1987), Meikle et al (1991) and Bellinger & Lahrer (1988). Furthermore, glycerol is the principal osmolyte in some filamentous fungi, algae, insects, crustaceans and vertebrates which indicates that there is a selective advantage to organisms using such low molecular mass solutes (Yancey et al, 1982 ;Hocking & Norton, 1983). As an osmolyte, glycerol offers a number of advantages : high glycerol concentrations confer a remarkable degree of protection to enzymes and macromolecular structure , and modification of proteins is unnecessary in order to function in concentrated intracellular solutions.…”

Section: Discussionmentioning

confidence: 99%

The water relations of growth and polyhydroxy alcohol production by ascomycetous yeasts

Eck

Prior

Brandt

1993

Journal of General Microbiology

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The response of 31 ascomycetous yeasts to a reduction in water activity (a,) adjusted with D-glucose or NaCl was investigated. The growth of most yeasts was more tolerant to glucose than to NaCl at equivalent a,. Zygosaccharomyces rouxii was the most osmotolerant yeast examined. Natural abundance 13C-NMR spectroscopy and HPLC analyses of eight yeasts indicated that glycerol and arabitol or mannitol were accumulated intracellularly in response to a, reduction. Pichia sorbitophila, Candida cacaoi, Candida magnoliae and Zygosaccharomyces bisporus responded to reduced a, by a decrease in specific growth rate and cell volume, and an accumulation of glycerol. The other polyol accumulated did not increase in concentration with a, reduction to the same degree as glycerol. A polyol concentration ratio (intra/extracellular) as high as 800-fold was attained across the membrane. Greater amounts of polyols were produced at equivalent a, values when adjusted with glucose than with NaCl. The ability to accumulate high concentrations of polyols appears to be the most important criterion in determining osmotolerance.

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“…Accumulation of progressively lower M , polyols in fungi grown over a range of decreasing a, has been found in mycelia of nonentomopathogenic fungi (Beever & Laracy, 1986 ;Kelly & Budd, 1991). Although accumulations of low M , polyols have frequently been reported in xerophilic fungi at reduced a, (Adler etal., 1782;Luard, 1982;Gadd etal., 1984;Hocking & Norton, 1983;Hocking, 1986), water relations of such extremophiles do not typify the situation in other fungi. Protein structure in halophiles is, for example, different from that of non-halophilic organisms such as the entomopathogens in the present study (Yancey etal., 1782;Kushner, 1986).…”

Section: Polyols and Trehalose In Conidia From Different Mediamentioning

confidence: 99%

Effect of carbohydrate type and concentration on polyhydroxy alcohol and trehalose content of conidia of three entomopathogenic fungi

1994

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The entomopathogenic fungi Beauveria bassiana, Metarhizium anisopliae and Paecilomyces farinosus were cultured on solid agar media containing different carbohydrate components (glycerol, glucose, trehalose or starch) at concentrations of < 142.7 g added carbon I-1 for 30 d at 25 "C. The water activity ( a, ) of the media ranged from 0925 to 0.998. Growth of M. anisopliae and P. farinosus was stimulated between 0975 and 0.995 a , on glucose media and that of P. farinosus at 0.975 aw on glycerol media. At < 0.970 a , growth of each fungal species was significantly reduced (P < 0.05). Polyhydroxy alcohols (polyols) and trehalose were extracted from conidia produced on different media and quantified using HPLC. Total polyol content of conidia produced on glucose media varied between 5-2 and 52-2 mg g-l for B. bassiana, 77.3 and 903 mg g-l for M. anisopliae, and 26-7 and 76-1 mg g-l for P. farinosus. The amounts of specific polyols in conidia varied significantly from media of different glucose concentrations. Mannitol was the predominant polyol in conidia of all three species, with conidia of M. anisopliae, for example, containing as much as 75.2 mg mannitol g-l when cultured on glucose media. The amount of the lower molecular mass polyols glycerol and erythritol was greater in conidia produced on glucose media with > 500 g added carbon I-' than that in conidia produced at lower glucose concentrations. Conidia contained between 1 0 8 and 20.8 mg glycerol plus erythritol g-' on glucose media with 142-7 g added carbon I-', depending on species. Conversely, conidia of B. bassiana and P. farinosus contained maximum amounts of trehalose (d 23-5 mg g-l) when produced on glucose media with < 500 g added carbon I-l, and trehalose content was considerably less at higher glucose concentrations. There were accumulations of glycerol and erythritol in conidia of all three species when grown on glycerol media with > 25.0 g added carbon I-l; conidia of B. bassiana contained up to 1540 mg glycerol plus erythritol g-l. When B. bassiana and P. farinosus were grown on trehalose media, conidia contained up to 222.1 mg trehalose g-'. By contrast, conidia of M. anisopliae contained < 17.0 mg trehalose g-1 under all conditions tested. The water availability of solutions of different polyols is discussed in relation to their potential to act in osmotic adjustment during germination. The ability to manipulate polyol and trehalose content of fungal propagules may be critical in enhancing the storage life and efficacy of biological control agents.

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Natural-abundance 13C Nuclear Magnetic Resonance Studies on the Internal Solutes of Xerophilic Fungi

Cited by 30 publications

References 25 publications

Osmotic adjustment in the filamentous fungus Aspergillus nidulans

Osmotic adjustment in the filamentous fungus Aspergillus nidulans

The water relations of growth and polyhydroxy alcohol production by ascomycetous yeasts

Effect of carbohydrate type and concentration on polyhydroxy alcohol and trehalose content of conidia of three entomopathogenic fungi

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