In vitro biofilm development of Streptococcus pneumoniae and formation of choline‐binding protein–DNA complexes

Abstract

Extracellular deoxyribonucleic acid (eDNA) is an essential component of bacterial biofilm matrices, and is required in their formation and maintenance. Extracellular DNA binds to exopolysaccharides or extracellular proteins, affording biofilms greater structural integrity. Recently, we reported evidence of intercellular eDNA-LytC complexes in pneumococcal biofilms. The LytC lysozyme is a member of the choline-binding family of proteins (CBPs) located on the pneumococcal surface. The present work shows that other CBPs, i.e. LytA, LytB, Pce, PspC and CbpF, which have a pI between 5 and 6, can bind DNA in vitro. This process requires the presence of divalent cations other than Mg(2+). This DNA binding capacity of CBPs appears to be independent of their enzymatic activity and, at least in the case of LytA, does not require the choline-binding domain characteristic of CBPs. Positively charged, surface-exposed, 25 amino acid-long peptides derived from the catalytic domain of LytB, were also found capable of DNA binding through electrostatic interactions. Confocal laser scanning microcopy revealed the existence of cell-associated LytB-eDNA complexes in Streptococcus pneumoniae biofilms. These and other findings suggest that these surface-located proteins of S. pneumoniae could play roles of varying importance in the colonization and/or invasion of human host where different environmental conditions exist.

Evidence of the presence of nucleic acids and β-glucan in the matrix of non-typeable Haemophilus influenzae in vitro biofilms

“…Together with our previous results3144, plus those of other authors on pneumococcal biofilms70, the present findings pave the way for detailed in vitro studies on more complex pneumococcal–NT Hi biofilms.…”

“…Previous studies have shown that eDNA binds extracellular proteins such as PilA (the type IV pilin protein)15 and the bacterial DNABII family of proteins (also known as histone-like proteins or Hlps)43. Recent results from our laboratory have shown that the choline-binding proteins of S. pneumoniae have the unexpected capacity to strongly bind DNA through electrostatic interactions; they may therefore be important in the early stages of biofilm formation3144. This might also be true for other bacteria.…”

Increased Zinc Availability Enhances Initial Aggregation and Biofilm Formation of Streptococcus pneumoniae

“…Pneumococcal autolysis can free DNA that could then contribute to biofilm formation as has been previously described (Steinmoen et al, 2002; Domenech et al, 2015). To determine if LytA is contributing to increased biofilm formation seen in the parental T4R strain, the effect of zinc on biofilm formation in a mutant strain lacking LytA (ΔLytA) was investigated.…”

“…Pneumococcus specifically has the ability to release extracellular DNA through the process of LytA-dependent autolysis (Steinmoen et al, 2002; Domenech et al, 2015). Domenech et al have published multiple studies highlighting the relationship between the choline-binding family of proteins and extracellular DNA in pneumococcal biofilms (Moscoso et al, 2006; Domenech et al, 2015). In order to investigate if LytA-dependent autolysis was contributing to our increasing biofilms in different concentrations of zinc, we utilized a mutant lacking LytA.…”

The Antitoxin Protein of a Toxin-Antitoxin System from Xylella fastidiosa Is Secreted via Outer Membrane Vesicles

“…Biofilm formation results in water deficiency, limitations in nutrient transport and death during later stages of infection (Rodrigues et al, 2013). This structure is involved in the pathogenicity of several species such as X. fastidiosa (Caserta et al, 2010; Voegel et al, 2010; Janissen et al, 2015), Neisseria meningitides (Arenas et al, 2015), Streptococcus pneumonia (Domenech et al, 2015), Salmonella enteric (O'Leary et al, 2015), and Pseudomonas syringae (Chowdhury and Jagannadham, 2013), conferring resistance to antibiotics and other chemicals used to control bacterial populations.…”