Av. Sarthy et al., PHENOTYPE IN CANDIDA-ALBICANS OF A DISRUPTION OF THE BGL2 GENE ENCODING A 1,3-BETA-GLUCOSYLTRANSFERASE, Microbiology, 143, 1997, pp. 367-376
The BGL2 gene encodes a unique 1,3-beta-glucosyltransferase (Bgl2p) pr
esent in the cell wall of Candida albicans and other fungi. Although b
elieved to be involved in cell wall assembly, disruption of the gene i
n Saccharomyces cerevisiae showed no apparent phenotype. We performed
sequential disruptions of the BGL2 loci in a homozygous ura3 clinical
isolate of C. albicans using the URA3 blaster method, in order to inve
stigate the role of Bgl2p in this dimorphic, pathogenic fungus. Strain
CACW-1 contained disruptions of both homologues of the BGL2 gene and
lacked Bgl2p, as assessed by protein extraction, SDS-PACE and Western
blot analysis, and enzyme assay; however, residual non-Bgl2p transfera
se activity was detected. CACW-1 was attenuated in virulence for mice
when compared to an isogenic parent strain, and fewer organisms were r
ecovered from the kidneys of infected animals. Additional phenotypic c
hanges included: (1) a dramatic increase in the sensitivity to the chi
tin synthesis inhibitor nikkomycin Z when CACW-1 cells were incubated
at 37 or 42 degrees C; (2) an 8.7 +/- 1.6% slower growth rate at 37 de
grees C for CACW-1 when compared to its isogenic parent; and (3) aggre
gation of CACW-1 cells during stationary phase and/or incubation of st
ationary phase cells in phosphate buffer. Characterization of SDS-extr
acted cell walls did not reveal any significant differences in the lev
els of 1,3-beta- or 1,6-beta-glucan. These data reveal that loss of Bg
l2p does have a phenotype in C. albicans, and indicate that (1) loss o
f Bgl2p function renders cells more dependent on chitin for wall integ
rity, and attenuates virulence (probably due to subtle changes in walt
structure), and (2) that additional 1,3-beta-glucosyltransferases are
present in the C. albicans BGL2 disruptant.