Biochemistry of Dimorphism in the Fungus Mucor

Sypherd, Paul S.; Borgia, Peter T.; Paznokas, John L.

doi:10.1016/s0065-2911(08)60415-4

Cited by 68 publications

(43 citation statements)

References 80 publications

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“…Mucor rouxii is a dimorphic fungus that grows either as a mycelium or like Saccharomyces cerevisiae depending on the environmental conditions (3,21,26). Irrespective of growth conditions, however, sporangiospores placed into an appropriate medium increase in volume by an isodiametric or spherical growth process termed phase I (4).…”

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confidence: 99%

“…Irrespective of growth conditions, however, sporangiospores placed into an appropriate medium increase in volume by an isodiametric or spherical growth process termed phase I (4). After this phase, spores start a distinct phase of polarized growth termed phase 11 (4), emitting either germ tubes (mycelial growth) or buds, depending on the environmental conditions (3,4,21,26). Syntheses of chitin (4) and proteins and RNA (7) occur exponentially with no appreciable change in rate through phases I and II of germination.…”

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DNA methylation and polyamines in regulation of development of the fungus Mucor rouxii

1988

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DNA from intact or spherically growing spores of Mucor rouxuii is highly methylated, whereas DNA from germlings has low levels of methylation. DNA from spores incubated with hydroxyurea or 1,4-diaminobutanone is also highly methylated. The reversal of the effect of 1,4-diaminobutanone by azacytidine correlated with DNA hypomethylation. These data suggest that the change in growth pattern from spherical to polarized correlates with the degree of DNA methylation and that this, in turn, may be controlled by polyamine levels.

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DNA methylation and polyamines in regulation of development of the fungus Mucor rouxii

1988

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“…(14); however, most of these measurements were made in cells shifted from CO2 to air. The shift from an anaerobic to an aerobic environment with both CO2 and 02 may lead to many changes independent of development (18). In this paper, the development of yeast or hyphae was done in the VOL.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, yeast forms are only found under anaerobic conditions with an excess of CO2 (1, 5). Although there are numerous studies on the carbon sources, atmosphere, and other environmental conditions that result in the formation of either yeast or hyphal tubes (1,5,18), there is very little work on the effect of the nitrogen sources on Mucor spp. dimorphism (15).…”

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Effect of L-amino acids on Mucor rouxii dimorphism

Leija¹,

Ruíz-Herrera²,

Mora³

1986

J Bacteriol

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Mucor rouxii organisms growing aerobically and exponentially on a well-defined minimal medium are able to differentiate as yeasts or as mycelia, depending on the amino acid used as the nitrogen source. When certain amino acids were used as the nitrogen source, spores differentiated only as hyphae, whereas other amino acids gave rise to other morphological forms having different ratios of yeasts to hyphae. In both hyphal and yeast cultures, an aerobic metabolism was predominant, as shown by determining several metabolic parameters such as oxygen tension, glucose consumption, ethanol production, and CO2 release. A complete conversion of yeasts to hyphae was obtained by the appropriate change in the amino acid used as nitrogen source. By preparing spheroplasts from mycelial cultures and transferring them to media with amino acids that induce yeast formation, a 50% yield in the reverse transformation was achieved. A correlation between the change in pH of the medium and cell morphology was observed in different growth conditions. Decrease in the pH of the medium preceded the appearance of hyphae. Also, when the initial pH of the medium was increased, aspartate-containing cultures developed mainly as mycelia, instead of yeasts, with a corresponding decrease in the final pH.Mucor rouxii organisms are able to grow in yeastlike or in filamentous forms, depending on the culture conditions. The growth requirements for the yeast phase of Mucor spp. are considerably more stringent and complex than are those for the hyphal phase (1). In addition, yeast forms are only found under anaerobic conditions with an excess of CO2 (1, 5). Although there are numerous studies on the carbon sources, atmosphere, and other environmental conditions that result in the formation of either yeast or hyphal tubes (1,5,18), there is very little work on the effect of the nitrogen sources on Mucor spp. dimorphism (15).The physiology and regulation of nitrogen assimilation in the fungus Neurospora crassa, and the enzymes involved have been extensively studied (4,(8)(9)(10)19). In our study on the enzymes responsible for ammonium assimilation in M. rouxii, we found unexpectedly that the appearance of different morphologies of M. rouxii depended on the L-amino acid used as the nitrogen source in the medium.In this paper, we show that the capacity of M. rouxii to differentiate as yeast or hyphae (or both) in aerobic cultures depended on the amino acid present as nitrogen source. We report our findings on (i) the growth rate, germination, and morphologies found, (ii) the interconversion of one cellular morphology into another, and (iii) the relationship between the morphological events induced by amino acids and the change of pH in the medium. MATERIALS AND METHODSStrain and media. M. rouxii IM80 was used throughout this study. The solid medium used was yeast extract peptone broth, supplemented with 112 mM glucose (YPG). The liquid medium was Vogel minimal medium (20) supplemented with 28 mM glucose. The nitrogen source used was either NH4Cl (25 mM) or ...

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“…they are able to grow as mycelium or as a yeast-like form according to the prevailing growth conditions, notably O2 tension and the type and concentration of the carbon source (see reviews by Bartnicki-Garcia, 1963 ;Sypherd et al, 1978 ;Inderlied et al, 1985 ;Ruiz-Herrera, 1985). In general, an anaerobic environment and high concentrations of fermentable carbon sources are associated with yeastlike growth, whereas mycelial growth requires aerobiosis and low concentrations of fermentable or non-fermentable carbon sources.…”

Section: Introductionmentioning

confidence: 99%

Environmental Control of the Respiratory System in the Dimorphic Fungus Mucor rouxii

1988

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Spores of Mucor rouxii had low levels of respiratory activity partially sensitive to cyanide and salicylhydroxamic acid (SHAM). They contained a full set of cytochromes but in low concentrations, especially cytochromes aa3. Aerobic growth induced a rapid increase in respiratory activity resistant to SHAM but fully sensitive to cyanide, and in the levels of cytochromes, mainly cytochromes aaj. These processes were subject to catabolite repression. Incubation under anaerobic conditions, independent of cell morphology, favoured the persistence of SHAM-sensitive respiration, and the maintenance of low levels of b and c cytochromes. No cytochromes au3 were formed under these conditions. CO-difference spectra suggested the presence of cytochrome o in higher levels in aerobic than in anaerobic cells.

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Biochemistry of Dimorphism in the Fungus Mucor

Cited by 68 publications

References 80 publications

DNA methylation and polyamines in regulation of development of the fungus Mucor rouxii

DNA methylation and polyamines in regulation of development of the fungus Mucor rouxii

Effect of L-amino acids on Mucor rouxii dimorphism

Environmental Control of the Respiratory System in the Dimorphic Fungus Mucor rouxii

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