To develop better molecular genetic tools for the diploid yeast Candida alb
icans, the suitability of the METIS gene as a visual selection marker was s
tudied. Both METIS alleles of C. albicans CAI-4 were isolated by functional
complementation of a Saccharomyces cerevisiae strain lacking the METIS gen
e. Growth of this complemented strain on Pb2+-containing medium was associa
ted with a colour shift of brown into white colonies. The METIS alleles of
C. albicans were located on chromosome 4 by pulsed-field gel electrophoresi
s and Southern blotting. A met15-deficient strain of C. albicans CAI-4 was
generated using the ura blaster technique. This strain showed a brown colon
y colour on Pb2+-containing medium, which corresponded with the colony colo
ur of a S, cerevisiae strain lacking the METIS gene. Unexpectedly, the met1
5-deficient strain of C. albicans still grew on methionine-depleted medium.
However, this growth was severely delayed. In addition, complementation of
this strain with an integrative or replicative plasmid containing either o
f the METIS alleles resulted in the formation of white transformants on Pb2
+-containing medium. These transformants grew very well on methionine-deple
ted medium. Colony sectoring was obtained with the replicative plasmid and
not with the integrative one. This study demonstrates that the METIS gene o
f C, albicans is suitable as a visual marker and therefore can be used to i
dentify transformants and study plasmid stability. GenBank Accession Nos fo
r MET15 nucleotide sequences are AF188273, AF188274 and AF188275, Copyright
(C) 2000 John Wiley & Sons, Ltd.