Chitin is one of major components of cell walls of many filamentous fungi. To investigate the roles of chitin metabolism in hyphal tip growth and conidial development, we cloned three chitin synthase genes (chs 1, chs 2, and chs 3) of filamentous fungus Rhizopus oligosporus which belongs to Zygomycetes, and investigated their expression patterns. The results suggested that chs 1 and chs 2 function in hyphal growth while chs 3 functions in an early stage of conidiation. We also cloned four chitin synthase genes (chs A, chs B, chs C, and chs D) of filamentous fungus Aspergillus nidulans which belongs to Ascomycetes, and disrupted them. chs B appears to function mainly in hyphal growth and chs A, chs C, and chs D mainly in the formation of conidiophores and/or conidiation.
We purified two chitinases (chitinase I and II) of R. oligosporus from culture supernatant in the late stage of culture when autolysis of hyphae was observed and cloned the genes (chi 1 and chi 2) encoding them. The structures of deduced products of chi 1 and chi 2 (Chi 1 and Chi 2) are similar to that of chitinase of Saccharomyces cerevisiae except that they have pro-sequences at their C-termini. Chi 1 and Chi 2 are classified as fungal-type chitinases. We also purified another chitinase (chitinase III) from actively growing hyphae of R. oligosporus and cloned the gene (chi 3) encoding it. Chi 3 is a bacterial-type chitinase. We cloned two chitinase genes (chi A and chi B) of A. nidulans and showed that chi A encodes a fungal-type chitinase while chi B encodes a bacterial-type chitinase. From the phenotypes of disruptants of chi A gene, it is suggested that chi A has roles in the normal germination of conidia and normal hyphal growth.

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In immunocompromised hosts such as AIDS patients systemic candidiasis and chronic mucocutaneous candidiasis are common infections. Among several putative virulence factors of C. albicans an aspartic proteinase secreted by this yeast has been thought to be primarily responsible for its pathogenicity. Although this possibility is supported by experimental data reported from several different laboratories, the actual pathogenetic role of C. albicans aspartic proteinase in the development of candidiasis remains unclear. We undertook the cDNA cloning of this enzyme and disrupted the gene. In this paper we report the structure, the expression of the gene, and biocharacteristics of the enzyme produced by the gene as a virulence factor. Comparison is made of the DNA and amino acid sequences among the related enzymes secreted by C. albicans including the one we cloned, and those of C. tropicalis and C. parapsilosis reported previously; the functions are also described.

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In the yeast Candida albicans karyotype variation among strains such as change in specific chromosome size or in the number of chromosomes is frequently observed. We have found one repetitive sequence (RPS) which might be involved in karyotypic variation. Sequences of several RPSs showed that the variability among them was derived from the variable number of repetitions of the inner repeating unit, alt. In investigating the RPS region, we found that another element distinguishable from RPSs neighbors the RPS region on a respective chromosome. Recently a new sequence, HOK, was isolated and its base sequence was determined.
Homology search of HOK showed a significant level of homology with a portion of the isocitrate dehydrogenase gene of Saccharomyces cerevisiae. We also detected that a part of HOK was transcribed by Northern analysis, though it had no corresponding size of an open reading frame in HOK. It is therefore assumed that the HOK transcript act as an RNA molecule.
Now we can browse and get a variety of information about Candida albicans from the Internet, including a restriction map using an Sfi I, alignment of fosmid clones, a list of cloned genes, and some molecular biological methods. We can also append a mailing list focusing on Candida and Candida research. Sharing the information will make Candida research easier and more familiar to many researcher.

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For germ tube formation in mid-exponential phase Candida albicans, two media were formulated: a glucose medium and an N-acetylglucosamine medium. We found that for germ tube formation to occur in the glucose medium, it was necessary to starve the mid-exponential phase cells in distilled water before transferring them to the medium. However, for the N-acetylglucosamine medium no starvation was necessary. These circumstances raise two questions: (1) Why is starvation needed to cause germ tube formation in the glucose medium? (2) Why is no starvation needed to do so in the N-acetylglucosamine medium? We have developed a hypothesis: when the organism was starved, yeast growth genes would be regulated. Moreover, when the N-acetylglucosamine medium was used, the same situation would transiently appear in the organism. We attempted to isolate common mRNAs from mid-exponential phase C. albicans which was starved or cultured in N-acetylglucosamine medium for a short time using a modified differential display of RT-PCR. Further experiments must be conducted to confirm this hypothesis.

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mRNA fingerprinting based on RT-PCR (reverse transcriptase-polymerase chain reaction) such as differential display (DD) and RAP (mRNA fingerprinting using arbitrarily primed PCR) are useful methods to identify differentially expressed genes. We adopted DD to identify the gene(s) involved in Candida albicans pathogenicity using highly (16240) and weakly (18084) virulent strains. More than 40 cDNA fragments were isolated. The deduced amino acid sequence of one fragment was highly homologous to Saccharomyces cerevisiae translation initiation factor (TIF). The TIF gene was isolated from the C. albicans genomic library. Its expression was nearly 2-fold higher in the 16240 strain as assessed by Northern blot analysis. At present, the link between TIF gene and virulence is not clearly understood. However, DD is a useful technique to isolate differentially expressed genes in C. albicans.

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Treatment failures in fungal infections have drawn attention recently to the problem of azole antifungal resistance and its underlying mechanisms. In most cases this failure is due to fluconazole- or azole-cross-resistant (fluconazole, ketoconazole and itraconazole) Candida albicans isolates. Energy-dependent drug efflux is emerging as an important mechanism of drug resistance in many organisms. A well-studied system is the human P-glycoprotein which is responsible for the multidrug resistance (MDR) of tumour cells to chemotherapeutic agents. There are several lines of evidence which indicate that proteins with structural similarities to drug pumps are involved in fluconazole resistance in C. albicans.
In this review paper, fluconazole uptake by C. albicans strains, cloning of genes encoding predicted drug efflux proteins and comparative expression of multidrug resistance genes in azole-sensitive and -resistant strains are described. Transformation of an azole-sensitive strain with a plasmid containing a potential drug pump gene is also described. Drug efflux, mediated by membrane-associated drug efflux pumps, can protect cells from a range of toxic compounds and therefore may confer single-step multidrug resistance.

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Dermatophytes isolated from patients at the Department of Dermatology of Asahikawa Medical College during the period Jan. 1990 to Dec. 1995 were analyzed. A total of 738 dermatophytoses patients were studied, accounting for 7.8% of all the outpatients. Male/female ratio was 3:2, and the greatest incidence was in the 5th decade of life. Among the 738, the most frequent was tinea pedis (74.3%), followed by tinea corporis (15.4%), tinea cruris (4.3%), tinea manuum (3.8%), tinea capitis (1.4%), kerion celsi (3 cases), tinea barbae (2 cases), and granuloma trichophyticum (1 case). The incidence of tinea pedis and tinea corporis was higher than that of our previous analysis during 1977-1989, whereas that of tinea cruris and kerion celsi had decreased. The isolates consisted of 312 strains (64.5%) of Trichophyton rubrum, 135 (27.9%) of T. mentagrophytes, 23 (4.7%) of Microsporum canis, 13 (2.6%) of T. verrucosum, and 1 (0.2%) of Epidermophyton floccosum.

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