Biofilm Formation byStreptococcus pneumoniae: Role of Choline, Extracellular DNA, and Capsular Polysaccharide in Microbial Accretion

Abstract

Streptococcus pneumoniae colonizes the human upper respiratory tract, and this asymptomatic colonization is known to precede pneumococcal disease. In this report, chemically defined and semisynthetic media were used to identify the initial steps of biofilm formation by pneumococcus during growth on abiotic surfaces such as polystyrene or glass. Unencapsulated pneumococci adhered to abiotic surfaces and formed a three-dimensional structure about 25 m deep, as observed by confocal laser scanning microscopy and low-temperature scanning electron microscopy. Choline residues of cell wall teichoic acids were found to play a fundamental role in pneumococcal biofilm development. The role in biofilm formation of choline-binding proteins, which anchor to the teichoic acids of the cell envelope, was determined using unambiguously characterized mutants. The results showed that LytA amidase, LytC lysozyme, LytB glucosaminidase, CbpA adhesin, PcpA putative adhesin, and PspA (pneumococcal surface protein A) mutants had a decreased capacity to form biofilms, whereas no such reduction was observed in Pce phosphocholinesterase or CbpD putative amidase mutants. Moreover, encapsulated, clinical pneumococcal isolates were impaired in their capacity to form biofilms. In addition, a role for extracellular DNA and proteins in the establishment of S. pneumoniae biofilms was demonstrated. Taken together, these observations provide information on conditions that favor the sessile mode of growth by S. pneumoniae. The experimental approach described here should facilitate the study of bacterial genes that are required for biofilm formation. Those results, in turn, may provide insight into strategies to prevent pneumococcal colonization of its human host.

The cidA murein hydrolase regulator contributes to DNA release and biofilm development in Staphylococcus aureus

“…DNase treatment has been shown to disrupt P. aeruginosa biofilm grown in vitro (35,46) and is used in combination with antibiotics to treat P. aeruginosa infections of cystic fibrosis patients (47). Treatment of streptococcal biofilm with DNase has also been shown to have a negative effect on biofilm adherence (41,48,49). These results correlate with our findings that DNase treatment had a greater ability to interfere with biofilm adherence in the wild-type S. aureus strain relative to the cidA mutant, presumably because the mutant biofilm contains less eDNA (Figs.…”

Ceragenins as Mimics of Endogenous Antimicrobial Peptides

“…The impact of biofilms, both bacterial and fungal, are increasingly recognized as threats to public health due to the fact that biofilm formation is involved in more than 60% of bacterial infections, as well as being recognized as a causative agent in most medical device-related infections [75,76]. In their biofilm forms, bacteria and fungi are resistant to most antimicrobials, due to decreased metabolism and the barrier provided by the extracellular matrix [77][78][79].…”

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

“…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).…”