Influence de la concentration du glucose et de l'azote sur la morphologie de Candida albicans et la formation de ses chlamydospores dans un milieu de culture synth�tique

Dujardin, L.; Walbaum, S.; Biguet, J.

doi:10.1007/bf00440617

Cited by 9 publications

(5 citation statements)

References 7 publications

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“…When grown in the presence of glucose at low pH values, the budding cells, also, apparently did not separate, which resulted in the formation of large clusters of multiple-budded cells or pseudohyphae. Similar modes of growth have been reported previously in response to glucose at lower temperatures (Soll & Bedell, 1978;Dujardin et al, 1980). It might be useful to use this phenomenon to distinguish between growing and non-growing cells at low pH or low temperatures.…”

Section: Discussionsupporting

confidence: 75%

The Role of Glucose in the pH Regulation of Germ-tube Formation in Candida albicans

Pollack¹,

Hashimoto²

1987

Microbiology

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It has been reported that Candida albicans can form germ-tubes only in the narrow pH range of 6-8, and that by changing only the pH one can regulate germ-tube formation. We found that the pH minimum for germ-tube formation could be dramatically lowered by eliminating the glucose present in many induction solutions. Lee's medium lacking glucose, ethanol, N-acetyl-D-glucosamine, and proline induced germ-tubes at pH values as low as 3 under most conditions. The presence of as little as 1 mM-glucose in these induction solutions was sufficient to cause the cells to grow either as yeasts with multiple buds or as pseudohyphae when the pH was 3.7. However, when C. albicans was grown in any of the above induction solutions (with the exception of ethanol), containing 200 mM-glucose buffered at pH 5.8, not only were germ-tubes formed, but their rate of formation and length were also increased. Preincubation of the cells in a solution buffered at pH 3.7 and containing 200 mM-glucose, before exposure to induction solutions lacking glucose at pH 3.7 or at pH 5.8, did not inhibit germ-tube formation. Likewise, addition of glucose after 45 min exposure to an induction solution was without effect. Theophylline and dibutyryl cAMP did not counteract the action of glucose. Other sugars which suppressed germ-tube formation at low pH were fructose, galactose, mannose, xylose, gluconic acid and the nonmetabolizable sugar 3-O-methylglucose. These results indicate that pH does not directly regulate dimorphism in C. albicans, and that glucose or its metabolites may play an important role.

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Section: Discussionsupporting

confidence: 75%

The Role of Glucose in the pH Regulation of Germ-tube Formation in Candida albicans

Pollack¹,

Hashimoto²

1987

Microbiology

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“…Chlamydospore formation is especially abundant on solid media under glass coverslips providing microaerophilic conditions (Dalmau inoculation technique). The presence of glucose inhibits chlamydospore formation, while nitrogen levels have no major influence (5). Light inhibits chlamydospore formation (6).…”

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confidence: 99%

Chlamydospore Formation in Candida albicans Requires the Efg1p Morphogenetic Regulator

1999

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Chlamydospore formation of the fungal pathogen Candida albicans was found to depend on the Efg1 protein, which regulates the yeast-hyphal transition. Isogenic mutants lacking EFG1or encoding T206A and T206E variants did not differentiate chlamydospores, while cek1, cph1, ortpk2 mutations had no effect. Furthermore, filamentation ofefg1 cph1 double mutants in microaerophilic conditions suggests a novel Efg1p/Cph1p-independent filamentation pathway inC. albicans.

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“…Morphological transitions that are triggered by nitrogen starvation include pseudohyphal growth of diploid S. cerevisiae (Gimeno et al, 1992) and the Gcn4-dependent filamentation by C. albicans (Tripathi et al, 2002). Some impact of nitrogen on chlamydosporulation has also been described for C. albicans (Jansons and Nickerson, 1970b; Dujardin et al, 1980b) but no such information is available for C. dubliniensis so far. Hence, we tested the effect of nutrient addition to chlamydospore-inducing corn meal tween (CM) agar and rice agar.…”

Section: Resultsmentioning

confidence: 99%

“…However, in Candida the term chlamydospore does not refer to a functional, but rather to a morphological unit: Although Candida chlamydospores resemble such spores and are high in lipid droplets for energy supply (Jansons and Nickerson, 1970a), they are not more resistant to heat, starvation, or dryness compared to yeast cells (Citiulo et al, 2009). Nevertheless, early studies reported a correlation between nutrient supply and induction of chlamydospore formation of the fungus (Jansons and Nickerson, 1970b) where glucose, in contrast to nitrogen, had a strong repressive effect (Dujardin et al, 1980b). Typical inducing media on the other hand are rich in complex carbon sources (e.g., corn or rice meal) and frequently contain detergents.…”

Section: Introductionmentioning

confidence: 99%

Candida species Rewired Hyphae Developmental Programs for Chlamydospore Formation

Böttcher

Pöllath

Staib³

et al. 2016

Front. Microbiol.

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Chlamydospore formation is a characteristic of many fungal species, among them the closely related human-pathogenic dimorphic yeasts Candida albicans and C. dubliniensis. Whereas function and regulation of filamentation are well-studied in these species, the basis of chlamydospore formation is mostly unknown. Here, we investigate the contribution of environmental and genetic factors and identified central proteins involved in species-specific regulation of chlamydosporulation. We show that specific nutrient levels strongly impact chlamydospore initiation, with starvation favoring sporulation and elevated levels of saccharides or peptone inhibiting it. Thresholds for these nutritional effects differ between C. albicans and C. dubliniensis, which explain species-specific chlamydospore formation on certain diagnostic media. A C. albicans nrg1Δ mutant phenocopied C. dubliniensis, putting Nrg1 regulation at the basis of species-specific chlamydospore formation under various conditions. By screening a series of potential chlamydospore regulators, we identified the TOR and cAMP pathways as crucial for sporulation. As rapamycin treatment blocked chlamydosporulation, a low basal Tor1 activity seems to be essential. In addition, TOR effector pathways play an important role, and loss of the NCR (nitrogen catabolite repression) gene regulators Gat1 and Gln3 reduced chlamydospore formation. A severe reduction was seen for a C. albicans gcn4Δ deletion strain, implicating a link between regulation of amino acid biosynthesis and chlamydospore development. On the other hand, deletion of the GTPase gene RAS1 and the adenylyl cyclase gene CYR1 caused a defect in chlamydospore formation that was mostly rescued by cAMP supplementation. Thus, cAMP-signaling is a second major pathway to control chlamydospore production. Finally, we confirmed light exposure to have a repressive effect on chlamydosporulation. However, permanent illumination only reduced, but not abolished chlamydospore production of C. albicans whereas C. dubliniensis sporulation was unaffected. In summary, we describe novel environmental factors which determine chlamydosporulation and propose a first model for the regulatory network of chlamydospore formation by different Candida species.

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Influence de la concentration du glucose et de l'azote sur la morphologie de Candida albicans et la formation de ses chlamydospores dans un milieu de culture synth�tique

Cited by 9 publications

References 7 publications

The Role of Glucose in the pH Regulation of Germ-tube Formation in Candida albicans

The Role of Glucose in the pH Regulation of Germ-tube Formation in Candida albicans

Chlamydospore Formation in Candida albicans Requires the Efg1p Morphogenetic Regulator

Candida species Rewired Hyphae Developmental Programs for Chlamydospore Formation

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