FURTHER CHARACTERIZATION OF STAPHYLOCOCCUS-EPIDERMIDIS TRANSPOSON MUTANTS DEFICIENT IN PRIMARY ATTACHMENT OR INTERCELLULAR-ADHESION

Biofilm formation is suggested to be the result of primary attachment of Staphylococcus epidermidis cells to a polymer surface followed by a ccumulation in multilayered cell clusters. Here we describe the furthe r characterization of transposon (Tn917) mutants of Staphylococcus epi dermidis O-47 having been biofilm-negative in a polystyrene microtiter plate adhesion assay. Among 5000 Tn917 insertion strains, we isolated four biofilm-negative mutants, each carrying one copy of Tn917. The m utants could be divided into two phenotypic classes: class A (mut1 and mut1a) and class B (mut2 and mut2a). Mutants of phenotype class A lac ked four cell surface proteins and were affected in the primary attach ment to polystyrene, but remained able to form multilayered cell clust ers and to produce PIA. Mutants of phenotype class B were able to atta ch to polystyrene, but did not form multilayered cell clusters nor pro duce PIA. The cell surface protein pattern relative to the wild type w as unchanged in class B mutants. On Congo red agar, the wild type and class A mutants formed black colonies (positive reaction on Congo red agar) while class B mutant colonies were red (negative reaction). The initial binding of cells to polystyrene and the ability to form multil ayered cell clusters were found to be phenotypically and genetically d istinct traits.