LACK OF CONSISTENT SHORT SEQUENCE REPEAT POLYMORPHISMS IN GENETICALLYHOMOLOGOUS COLONIZING AND INVASIVE CANDIDA-ALBICANS STRAINS

Short sequence repeats (SSRs), potentially representing variable numbe rs of tandem repeat (VNTR) loci, were identified for the human-pathoge nic yeast species Candida albicans by computerized DNA sequence scanni ng. The individual SSR regions were investigated in different clinical isolates of C. albicans. Most of the C. albicans SSRs were identified as genuine VNTRs. They appeared to be present in multiple allelic var iants and were demonstrated to be diverse in length among nonrelated s trains. As such, these loci provide adequate targets for the molecular typing of C, albicans strains. VNTRs encountered in other microbial s pecies sometimes participate in regulation of gene expression and func tion as molecular switches at the transcriptional or translational lev el. Interestingly, the VNTRs identified here often encode polyglutamin e stretches and are frequently located within genes potentially involv ed in the regulation of transcription. DNA sequencing of these VNTRs d emonstrated that the length variability was restricted to the CAA/CAG repeats encoding the polyglutamine stretches. For these reasons, paire d C. albicans isolates of similar genotype, either found as noninvasiv e colonizers or encountered in an invasive state in the same individua l, were studied with respect to potentially invasion-related alteratio ns in the VNTR profiles. However, none of the VNTRs analyzed thus far varied systematically,vith the transition from colonization to invasio n. In contrast to the situation described for some prokaryotic species , this finding suggests that VNTRs of C. albicans may not simply funct ion as contingency loci related to straightforward on/off regulation o f invasion-related gene expression.