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The intestinal resident Candida glabrata opportunistically infects humans. However few genetic factors for adaptation in the intestine are identified in this fungus. Here we describe the C. glabrata CYB2 gene encoding lactate dehydrogenase as an adaptation factor for survival in the intestine. CYB2 was identified as a virulence factor by a silkworm infection study. To determine the function of CYB2, we analysed in vitro phenotypes of the mutant Δcyb2. The Δcyb2 mutant grew well in glucose medium under aerobic and anaerobic conditions, was not supersensitive to nitric oxide which has fungicidal-effect in phagocytes, and had normal levels of general virulence factors protease, lipase and adherence activities. A previous report suggested that Cyb2p is responsible for lactate assimilation. Additionally, it was speculated that lactate assimilation was required for Candida virulence because Candida must synthesize glucose via gluconeogenesis under glucose-limited conditions such as in the host. Indeed, the Δcyb2 mutant could not grow on lactate medium in which lactate is the sole carbon source in the absence of glucose, indicating that Cyb2p plays a role in lactate assimilation. We hypothesized that Cyb2p-mediated lactate assimilation is necessary for proliferation in the intestinal tract, as the intestine is rich in lactate produced by bacteria flora, but not glucose. The Δcyb2 mutant showed 100-fold decreased adaptation and few cells of Saccharomyces cerevisiae can adapt in mouse ceca. Interestingly, C. glabrata could assimilate lactate under hypoxic conditions, dependent on CYB2, but not yeast S. cerevisiae. Because accessible oxygen is limited in the intestine, the ability for lactate assimilation in hypoxic conditions may provide an advantage for a pathogenic yeast. From those results, we conclude that Cyb2p-mediated lactate assimilation is an intestinal adaptation factor of C. glabrata. [ABSTRACT FROM AUTHOR]

Diazobenzoic acid B (DBB), also known as diazonium blue B or fast blue B, can be used to distinguish basidiomycetous yeasts from ascomycetes. This chemical has long been used for the taxonomic study of yeast species at the phylum level, but the mechanism underlying the DBB staining remains unknown. To identify molecular targets of DBB staining, we isolated Agrobacterium tumefaciens-mediated insertional mutants of Cryptococcus neoformans, a basidiomycetous pathogenic yeast, which were negative to DBB staining. In one of these mutants, we found that the PMT2 gene, encoding a protein-O-mannosyltransferase, was interrupted by a T-DNA insertion. A complete gene knockout of the PMT2 gene revealed that the gene was responsible for DBB staining in C. neoformans, suggesting that one of the targets of Pmt2-mediated glycosylation is responsible for interacting with DBB. We also determined that Cryptococcus gattii, a close relative of C. neoformans, was not stained by DBB when the PMT2 gene was deleted. Our finding suggests that the protein-O-mannosylation by the PMT2 gene product is required for DBB staining in Cryptococcus species in general. We also showed that glycosylation in Cryptococcus by Pmt2 plays important roles in controlling cell size, resistance to high temperature and osmolarity, capsule formation, sexual reproduction, and virulence. [ABSTRACT FROM AUTHOR]