ABSTRACT
In
Candida parapsilosis
, biofilm formation is considered to be a major virulence factor. Previously, we determined the ability of 33 clinical isolates causing bloodstream infection to form biofilms and identified three distinct groups of biofilm-forming strains (negative, low, and high). Here, we establish two different biofilm structures among strains forming large amounts of biofilm in which strains with complex spider-like structures formed robust biofilms on different surface materials with increased resistance to fluconazole. Surprisingly, the transcription factor Bcr1, required for biofilm formation in
Candida albicans
and
C. parapsilosis
, has an essential role only in strains with low capacity for biofilm formation. Although
BCR1
leads to the formation of more and longer pseudohyphae, it was not required for initial adhesion and formation of mature biofilms in strains with a high level of biofilm formation. Furthermore, an additional phenotype affected by
BCR1
was the switch in colony morphology from rough to crepe, but only in strains forming high levels of biofilm. All
bcr1
Δ/Δ mutants showed increased proteolytic activity and increased susceptibility to the antimicrobial peptides protamine and RP-1 compared to corresponding wild-type and complemented strains. Taken together, our results demonstrate that biofilm formation in clinical isolates of
C. parapsilosis
is both dependent and independent of
BCR1
, but even in strains which showed a
BCR1
-independent biofilm phenotype,
BCR1
has alternative physiological functions.
Characterization of secreted aspartyl proteases in Candida parapsilosis
