Differential Roles of Poly- N -Acetylglucosamine Surface Polysaccharide and Extracellular DNA in Staphylococcus aureus and Staphylococcus epidermidis Biofilms

Abstract

Staphylococcus aureus and Staphylococcus epidermidis are major human pathogens of increasing importance due to the dissemination of antibiotic-resistant strains. Evidence suggests that the ability to form matrixencased biofilms contributes to the pathogenesis of S. aureus and S. epidermidis. In this study, we investigated the functions of two staphylococcal biofilm matrix polymers: poly-N-acetylglucosamine surface polysaccharide (PNAG) and extracellular DNA (ecDNA). We measured the ability of a PNAG-degrading enzyme (dispersin B) and DNase I to inhibit biofilm formation, detach preformed biofilms, and sensitize biofilms to killing by the cationic detergent cetylpyridinium chloride (CPC) in a 96-well microtiter plate assay. When added to growth medium, both dispersin B and DNase I inhibited biofilm formation by both S. aureus and S. epidermidis. Dispersin B detached preformed S. epidermidis biofilms but not S. aureus biofilms, whereas DNase I detached S. aureus biofilms but not S. epidermidis biofilms. Similarly, dispersin B sensitized S. epidermidis biofilms to CPC killing, whereas DNase I sensitized S. aureus biofilms to CPC killing. We concluded that PNAG and ecDNA play fundamentally different structural roles in S. aureus and S. epidermidis biofilms.

Phage-induced lysis enhances biofilm formation in Shewanella oneidensis MR-1

“…Since that time, there has been emerging evidence from numerous studies on different bacterial species that identify eDNA as a common structural component in biofilm formation, although its exact role still remains unknown. As demonstrated here for S. oneidensis MR-1, eDNA is already involved in early attachment events, similar to what has been reported for other species (Whitchurch et al, 2002;Izano et al, 2008;Vilain et al, 2009;Harmsen et al, 2010;Lappann et al, 2010). Recent studies on Bacillus cereus, Listeria monocytonogenes and Staphylococcus epidermidis suggest that the bacterial cell surface may be decorated with DNA, resulting in acid-base interactions that increase the ability for either cell-cell and cell-surface interactions (Vilain et al, 2009;Das et al, 2010;Harmsen et al, 2010).…”

“…In contrast, the significance of eDNA for cellular attachment and structural integrity has more recently been recognized for an increasing number of Gram-negative and Grampositive species (Whitchurch et al, 2002;Steinberger and Holden, 2005;Allesen-Holm et al, 2006;Moscoso et al, 2006;Jurcisek and Bakaletz, 2007;Qin et al, 2007;Izano et al, 2008;Thomas et al, 2008;Heijstra et al, 2009;Vilain et al, 2009;Harmsen et al, 2010;Lappann et al, 2010). Release of DNA in bacterial biofilms has mainly been attributed to the lysis of a cellular subpopulation, mediated by the activity of autolysis systems (Allesen-Holm et al, 2006;Rice et al, 2007;Thomas et al, 2008Thomas et al, , 2009Mann et al, 2009).…”

Biofilm characteristics of Staphylococcus epidermidis isolates associated with device-related meningitis

“…Further investigations into the role of S. epidermidis cellsurface adhesins, as well as examining the global regulatory systems that control their expression, are likely to lend more insight into the contribution that protein factors have to the biofilm-forming process. In addition to PIA and protein, extracellular DNA has also been shown to be important in stabilizing the structure (Izano et al, 2008).Our findings indicate that both polysaccharide and protein are important in the development and maintenance of a mature biofilm in CSF isolates deemed to be clinically significant and ica + /aap + , but this appears to be complex and variable. We did not include ica + /aap 2 isolates, as these did not form biofilm or produce PIA and were predominantly clonal, and the number of isolates studied was relatively small.…”

“…Further investigations into the role of S. epidermidis cellsurface adhesins, as well as examining the global regulatory systems that control their expression, are likely to lend more insight into the contribution that protein factors have to the biofilm-forming process. In addition to PIA and protein, extracellular DNA has also been shown to be important in stabilizing the structure (Izano et al, 2008).…”

Sticky Situations: Key Components That Control Bacterial Surface Attachment

“…Whitchurch et al (166) first demonstrated that P. aeruginosa PAO1 biofilm formation was significantly reduced under flowing conditions in the presence of DNase. eDNA has been subsequently shown to contribute to biofilm formation by clinical P. aeruginosa isolates as well as by a variety of bacterial species, including Staphylococcus epidermidis, through analyses of biofilm formation by lysis-defective mutants and of DNA removal from the biofilm matrix (67,117,133,146,150). The contribution of eDNA to attachment and biofilm formation, however, appears to be temporal: experiments utilizing DNase I have suggested that cells in young PAO1 biofilms are held together by eDNA, whereas the cells in more-mature PAO1 biofilms are held together primarily by components other than eDNA (98,166).…”