ALBERT

Description: Biofilm-forming microorganisms switch between two forms: free-living planktonic and sessile multicellular. Sessile communities of yeast biofilms in liquid medium provide a primitive example of multicellularity and are clinically important because biofilms tend to have other growth characteristics than free-living cells. We investigated the genetic basis for yeast, Saccharomyces cerevisiae , biofilm on solid surfaces in liquid medium by screening a comprehensive deletion mutant collection in the 1278b background and found 71 genes that were essential for biofilm development. Quantitative northern blots further revealed that AIM1 , ASG1 , AVT1 , DRN1 , ELP4 , FLO8 , FMP10 , HMT1 , KAR5 , MIT1 , MRPL32 , MSS11 , NCP1 , NPR1 , PEP5 , PEX25 , RIM8 , RIM101 , RGT1 , SNF8 , SPC2 , STB6 , STP22 , TEC1 , VID24 , VPS20 , VTC3 , YBL029W , YBL029C-A , YFL054C , YGR161W-C , YIL014C-A , YIR024C , YKL151C , YNL200C , YOR034C-A , and YOR223W controlled biofilm through FLO11 induction. Almost all deletion mutants that were unable to form biofilms in liquid medium also lost the ability to form surface-spreading biofilm colonies (mats) on agar and 69% also lost the ability to grow invasively. The protein kinase A isoform Tpk3p functioned specifically in biofilm and mat formation. In a tpk3 mutant, transcription of FLO11 was induced three-fold compared with wild-type, but biofilm development and cell–cell adhesion was absent, suggesting that Tpk3p regulates FLO11 positive posttranscriptionally and negative transcriptionally. The study provides a resource of biofilm-influencing genes for additional research on biofilm development and suggests that the regulation of FLO11 is more complex than previously anticipated.