Trichophyton rubrum and T. violaceum are prevalent agents of human dermatophyte infections, the former being found on glabrous skin and nail, while the latter is confined to the scalp. The two species are phenotypically different but are highly similar phylogenetically. The taxonomy of dermatophytes is currently being reconsidered on the basis of molecular phylogeny. Molecular species definitions do not always coincide with existing concepts which are guided by ecological and clinical principles. In this article, we aim to bring phylogenetic and ecological data together in an attempt to develop new species concepts for anthropophilic dermatophytes. Focus is on the T. rubrum complex with analysis of rDNA ITS supplemented with LSU, TUB2, TEF3 and ribosomal protein L10 gene sequences. In order to explore genomic differences between T. rubrum and T. violaceum, one representative for both species was whole genome sequenced. Draft sequences were compared with currently available dermatophyte genomes. Potential virulence factors of adhesins and secreted proteases were predicted and compared phylogenetically. General phylogeny showed clear gaps between geophilic species of Arthroderma, but multilocus distances between species were often very small in the derived anthropophilic and zoophilic genus Trichophyton. Significant genome conservation between T. rubrum and T. violaceum was observed, with a high similarity at the nucleic acid level of 99.38 % identity. Trichophyton violaceum contains more paralogs than T. rubrum. About 30 adhesion genes were predicted among dermatophytes. Seventeen adhesins were common between T. rubrum and T. violaceum, while four were specific for the former and eight for the latter. Phylogenetic analysis of secreted proteases reveals considerable expansion and conservation among the analyzed species. Multilocus phylogeny and genome comparison of T. rubrum and T. violaceum underlined their close affinity. The possibility that they represent a single species exhibiting different phenotypes due to different localizations on the human body is discussed.

The two-component histidine kinase Chk1p of Candida albicans has been implicated in the regulation of cell wall biosynthesis. Deletion of CHK1 results in avirulence that in part may be due to the increased sensitivity of mutant strains to polymorphonuclear leukocytes. The mutant also does not adhere to human oesophageal tissue in vitro, probably as a consequence of its altered cell wall. In the current study, a CHK1 promoter-lacZ reporter (CHK1prlacZ) construct was expressed in wild-type C. albicans strain CAI4 and in two-component signal transduction mutants to determine the effect of environmental stress conditions on the regulation of CHK1 and the co-regulatory activities among these proteins. It is shown that lacZ expression varied according to the type of growth conditions and incubation time; expression was also influenced by the strain background. lacZ expression in CAI4 was greater at 37 6C and at a pH of 3?5 and in the presence of 4 mM H 2 O 2 , 0?1 mM menadione, 10 % serum or 1?5 M NaCl compared to cells grown at 30 or 42 6C. The increases in expression were time-dependent and not observed until cells were incubated for 120 min in these conditions (P<0?05). As a correlate of the increase in transcription of CHK1-lacZ in the presence of H 2 O 2 , the chk1 mutant was more sensitive than wild-type and revertant cells to H 2 O 2 in vitro. In addition to strain CAI4, we also measured CHK1p-lacZ reporter activity of mutants deleted in genes encoding other two-component proteins such as the response regulator gene SSK1, the histidine kinases, SLN1 and NIK1, and the HOG1 MAP kinase. Of these proteins, Ssk1p and Sln1p are presumed to mediate phosphotransfer to the HOG1 [hyperosmotic glycerol] MAP kinase pathway during oxidative and perhaps osmotic stress in C. albicans. Compared to strain CAI4, lacZ reporter activity increased significantly in the ssk1 mutant under all growth conditions after a 10 and 120 min incubation (P<0?0001). lacZ expression in the ssk1 mutant was less at 42 6C compared to all other growth conditions (P<0?05). Furthermore, lacZ reporter activity also increased in the hog1 mutant of C. albicans. These data suggest that SSK1 and HOG1 indirectly or directly negatively regulate CHK1 under most growth conditions tested. In the sln1 mutant, downregulation of CHK1 was observed in all growth conditions compared to strain CAI4 (P<0?05), while regulation of lacZ in the nik1 mutant was similar to strain CAI4 except when cells were incubated in the presence of 4 mM H 2 O 2 for 120 min (P<0?05). Western blot analysis was used to determine the role of Chk1p in phosphorylation of Hog1p under oxidative or osmotic stress. It was found that Hog1p was phosphorylated in the chk1 mutant similar to wild-type CAF2-1 cells, although the temporal events of phosphorylation differed slightly in mutant cells. These results show that transcription of CHK1, as measured by the lacZ reporter assay, is statistically increased when cells are exposed to several types of stress or when incubated in 10 % serum in a mutant-sp...

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