Extracellular lipolytic activity enabled the human pathogen Candida albicans to grow on lipids as the sole source of carbon. Nine new members of a lipase gene family (LIP2-LIP10) with high similarities to the recently cloned lipase gene LIP1 were cloned and characterised. The ORFs of all ten lipase genes are between 1281 and 1416 bp long and encode highly similar proteins with up to 80% identical amino acid sequences. Each deduced lipase sequence has conserved lipase motifs, four conserved cysteine residues, conserved putative N-glycosylation sites and similar hydrophobicity profiles. All LIP genes, except LIP7, also encode an N-terminal signal sequence. LIP3-LIP6 were expressed in all media and at all time points of growth tested as shown by Northern blot and RT-PCR analyses. LIP1, LIP3, LIP4, LIP5, LIP6 and LIP8 were expressed in medium with Tween 40 as a sole source of carbon. However, the same genes were also expressed in media without lipids. Two other genes, LIP2 and LIP9, were only expressed in media lacking lipids. Transcripts of most lipase genes were detected during the yeast-to-hyphal transition. Furthermore, LIP5, LIP6, LIP8 and LIP9 were found to be expressed during experimental infection of mice. These data indicate lipid-independent, highly flexible in vitro and in vivo expression of a large number of LIP genes, possibly reflecting broad lipolytic activity, which may contribute to the persistence and virulence of C. albicans in human tissue.

Secreted lipases of Candida albicans are encoded by a gene family with at least 10 members (LIP1-LIP10). The expression pattern of this multigene family was investigated using reverse transcription polymerase chain reaction in experimental infections and in samples of patients suffering from oral candidosis. The findings illustrate that individual lipase genes are differentially regulated in a mouse model of systemic candidosis with some members showing sustained expression and others being transiently expressed or even silent. The lipase gene expression profile depended on the stage of infection rather than on the organ localization. This temporal regulation of lipase gene expression was also detected in an experimental model of oral candidosis. Furthermore, the expression of candidal lipase genes in human specimens is shown for the first time.

No abstract

The production of lipases can affect microbial fitness and virulence. We examined the role of the lipase 8 (LIP8) gene in the virulence of Candida albicans by constructing ⌬lip8 strains by the URA-blaster disruption method. Reverse transcription-PCR experiments demonstrated the absence of LIP8 expression in the homozygous knockout mutants. Reconstituted strains and overexpression mutants were generated by introducing a LIP8 open reading frame under control of a constitutive actin promoter. Knockout mutants produced more mycelium, particularly at higher temperatures and pH >7. Diminished LIP8 expression resulted in reduced growth in lipid-containing media. Mutants deficient in the LIP8 gene were significantly less virulent in a murine intravenous infection model. The results clearly indicate that Lip8p is an important virulence factor of C. albicans.Lipases catalyze both the hydrolysis and synthesis of triacylglycerols (4). Many of these enzymes are characterized by stability at high temperatures and in organic solvents, high enantioselectivity, and resistance to proteolysis, which make them ideal candidates for diverse commercial applications. In addition to the industrial uses of lipases, there is an evolving literature on their role as important microbial virulence factors (3, 42). The putative roles of microbial extracellular lipases include digestion of lipids for nutrient acquisition, adhesion to host cells and host tissues, synergistic interactions with other enzymes, nonspecific hydrolysis due to additional phospholipolytic activities, initiation of inflammatory processes by affecting immune cells, and self-defense mediated by lysing competing microflora (37, 43). Extracellular lipases have been proposed to be potential virulence factors of bacterial pathogens, including Staphylococcus aureus (47), Staphylococcus epidermidis (24), Propionibacterium acnes (26), and Pseudomonas aeruginosa (18), as well as pathogenic fungi, such as Malassezia furfur (33), Hortaea werneckii (13), and Candida species (37,43).Candida albicans is recognized as the leading opportunistic pathogen involved in oral, vaginal, and systemic infections. It is the fourth most common cause of bloodstream infection in the United States and has a high attributable mortality rate (32). Besides yeast-to-hypha transition, adhesion factors, surface hydrophobicity, phenotypic switching, thigmotropism, and molecular mimicry (7), the secretion of hydrolytic enzymes like proteinases or lipases may also affect C. albicans virulence. Although the secretion of aspartic proteinases (Sap1p to Sap10p) has been shown to be a key virulence determinant of C. albicans (15,27,29,38,41,45), limited information is available about the involvement of lipases in Candida infection.Extracellular lipase activity of C. albicans was first described in 1965 (53), and the first lipase gene, LIP1, was identified in 1997 (11). Results of Southern blot analysis using LIP1 as a probe under low-stringency conditions suggested the existence of a larger lipase gene family. More...

In 1995, Candida dubliniensis was described as a new species in the genus Candida. Its close relationship to C. albicans has proved problematic in the identification of C. dubliniensis in clinical specimens. The objective of this study was to determine if reproducible differentiation between both species can be obtained by phenotypic assays. Therefore, 100 strains from 86 patients with the ability to produce chlamydospores were examined with different methods including API ID 32 C, colour development on CHROMagar, chlamydospore formation on Staib agar, growth at different temperatures and germ tube formation at 39 degrees C. Additionally, polymerase chain reaction (PCR) was used as gold standard. Six of the investigated strains were C. dubliniensis. The results suggest that there is still no single phenotypic method satisfactory to distinguish between C. albicans and C. dubliniensis.