The Studies Of Systematics And Nomenclature Of Candida Rugosa And Its Relevant Species

Objectives:1.To discuss the accurate taxonomic relationship between Candida rugosa and relevant species by comprehensive phylogenic methods.2.To analyze the veracity and the rationality of the recent taxonomic relationship between Candida rugosa and relevant species.3.To evaluate and correct the taxonomic renames of Candida rugosa and its related species strains with both our study and recent report from some species belonging to Diutina genus.Methods:1.Twentie-four strains including Candida rugosa and its relevant species strains were selected for this study.Morphological identification and CHORMagar Candida culture were observed.2.API 20 C yeast identification test was applied.3.The drug susceptibility test of clinical Candida rugosa and its relevant species isolates was designed by applying yeast trace dilution method in M27-A3 program which is formulated by CLSI.4.Molecular phylogeny by mutilocus sequence typing(MLST)using five house-keeping genes were processed with Candida rugosa type strains and relevant species isolates.Results:1.The morphology characteristics of the tested strains in this research were similar;white,smooth or wrinkled colonies can be observed;in addition,the colony color of most Candida rugosa and relevant species on CHORMagar were blue-green except that Candida pseudorugosa was green-purple.2.Compared Candida rugosaand its relevant species' type strains,their carbon sources assimilation results showed less differences in API 20 C test.3.All strains of Candida rugosa,Candida mesorugosa and Candida pseudorugosa were sensitive to Amphotericin B,Fluconazole and 5-Flucytosine;the strains of Candida neorugosa were susceptible-dose dependent to Itraconazole,while sensitive to the three other broad spectrum antifungal drugs.4.Compared to the phylogenetic tree based on ITS sequence,the phylogenetic tree built on MLST showed three statistically well-supported clades inferred with high bootstrap support: A Clade,which contained Candida rugosa and Candida mesorugosa,B Clade contained by Candida neorugosa and C clade formed by Candida pseudorugosa.5.In this research,the position of the tested type strains in the phylogenetic tree were same as the ones showed in Khunnamwong and Lertwattanasakul's report;this result further verified the rationality of the statement which presented that Candida rugosa and three relevant species should belong to Diutina genus.6.The morphological characteristics of Diutina mesorugosa strains and Diutina rugosa strains had no differences;the carbon sources assimilation results of them were consistent;there were seven strains which were named Candida mesorugosa belonged to the clade of Candida rugosa;and the sequence similarities of Diutina rugosa strains and Diutina mesorugosa strains ranged from 98.1 to 98.9%.Conclusion:1.MLST analysis can more accurately speculate the evolutionary relationships between related strains.2.Through the comprehensive phylogeny in this study,Candida mesorugosa shows very close taxonomic position to Candida rugosa,which indicates that Candida rugosa and Candida mesorugosa belong to the same species;combining the recent reported rename proposal,we suggest that Candida mesorugosa should be classified into the species of Diutina rugosa.Diutina neorugosa and Diutina pseudorugosa still belong to different species in Diutina genus.3.The result demonstrates that the taxonomic identification of some similar Saccharomycetes strains should depend on the systemic analyses of both phenotypic and genotypic studies.