Glucose-Related Dissociation between icaADBC Transcription and Biofilm Expression by Staphylococcus epidermidis : Evidence for an Additional Factor Required for Polysaccharide Intercellular Adhesin Synthesis

Abstract

Biofilm formation in Staphylococcus epidermidis depends, in the majority of the strains, on the activity of the icaADBC locus. The expression of the operon that encodes the synthetic enzymes of the intercellular polysaccharide adhesin (PIA) depends on a variety of exogenic environmental conditions and is, at least in part, regulated by the alternative sigma factor B . We investigated the transcriptional regulation of the ica operon and the respective phenotypes expressed under growth conditions differing in the content of glucose in the growth medium. In the presence of glucose, S. epidermidis exhibited a PIA-and biofilm-positive phenotype whereas ica transcription was down-regulated in the postexponential and stationary phases of growth. Surprisingly, maximum transcription of ica was detectable in the stationary phase of growth in the absence of glucose despite the expression of a PIA-and biofilm-negative phenotype. In vitro enzymatic assays and phenotypic characterization showed that the abundant amount of ica mRNA was functionally active because induction of stationary-phase cells with glucose led to immediate PIA synthesis. Induction of biofilm formation could be completely inhibited by chloramphenicol, which, given at a later stage of biofilm accumulation, also inhibited further development of preformed biofilm, indicating that continuous translation of an additional, icaADBC-independent factor is required for the expression of a biofilm-positive phenotype.

Signals, Regulatory Networks, and Materials That Build and Break Bacterial Biofilms

“…For some bacteria, glucose and related sugars activate multilayer biofilm formation, while for others they serve as inhibitors of this type of surface attachment. Bacteria in the former group include Streptococcus mutans, Staphylococcus aureus, and Staphylococcus epidermidis (75,203,284,286).…”

Control of Glucose- and NaCl-Induced Biofilm Formation by rbf in Staphylococcus aureus

“…The presence of PIA has been correlated with pathogenesis, and mice vaccinated with PIA are protected from subsequent S. aureus challenge (28). However, PIA alone is not sufficient for biofilm formation; an additional factor independent of icaADBC gene expression in S. epidermidis also is required (7). It is likely that this additional factor is the 140-kDa protein, described earlier as the accumulationassociation protein, which enhances biofilm formation in S. epidermidis (14).…”

“…IcaR recently was shown to bind to the promoter region upstream of the icaA gene (15). In contrast, the effects of glucose and NaCl are not mediated through icaR (3,7). Environmental stresses are also likely to be mediated through the alternative transcriptional sigma factor B .…”

Structural study of TcaR and its complexes with multiple antibiotics from Staphylococcus epidermidis

“…The production of PIA depends on the expression of the icaADBC operon, which encodes three membrane proteins (IcaA, IcaD, and IcaC) (6)(7)(8). The ica operon is negatively regulated by a repressor encoded by an upstream gene of IcaR (9)(10)(11).…”