Contribution of Choline-Binding Proteins to Cell Surface Properties of Streptococcus pneumoniae

Abstract

Nonspecific interactions related to physicochemical properties of bacterial cell surfaces, such as hydrophobicity and electrostatic charge, are known to have important roles in bacterium-host cell encounters. Streptococcus pneumoniae (pneumococcus) expresses multiple, surface-exposed, choline-binding proteins (CBPs) which have been associated with adhesion and virulence. The purpose of this study was to determine the contribution of CBPs to the surface characteristics of pneumococci and, consequently, to learn how CBPs may affect nonspecific interactions with host cells. Pneumococcal strains lacking CBPs were derived by adapting bacteria to a defined medium that substituted ethanolamine for choline. Such strains do not anchor CBPs to their surface. Cell surface hydrophobicity was tested for the wild-type and adapted strains by using a biphasic hydrocarbon adherence assay, and electrostatic charge was determined by zeta potential measurement. Adherence of pneumococci to human-derived cells was assessed by fluorescence-activated cell sorter analysis. Strains lacking both capsule and CBPs were significantly more hydrophobic than nonencapsulated strains with a normal complement of CBPs. The effect of CBPs on hydrophobicity was attenuated in the presence of capsule. Removal of CBPs conferred a greater electronegative net surface charge than that which cells with CBPs possessed, regardless of the presence of capsule. Strains that lack CBPs were poorly adherent to human monocytelike cells when compared with wild-type bacteria with a full complement of CBPs. These results suggest that CBPs contribute significantly to the hydrophobic and electrostatic surface characteristics of pneumococci and may facilitate adherence to host cells partially through nonspecific, physicochemical interactions.

d -Alanylation of Teichoic Acids Promotes Group A Streptococcus Antimicrobial Peptide Resistance, Neutrophil Survival, and Epithelial Cell Invasion

“…We hypothesize that the incorporation of positive charges on the bacterial cell surface promotes interaction with the negatively charged host cell surface. An analogous situation may exist in Streptococcus pneumoniae, where removal of surface choline-binding proteins was associated with a net increase in negative charge on the bacterial surface and decreased adherence to eukaryotic cells (47).…”

Variation in Streptococcus pneumoniae susceptibility to human antimicrobial peptides may mediate intraspecific competition

“…For example, increasing the positive charge of the membrane by D-alanylation of lipoteichoic acids, catalysed by the dlt operon, [20,45] decreases AMP susceptibility. Similarly, deletion of choline-binding proteins, such as LytA, increases pneumococcal susceptibility to AMPs [47]. In addition, pneumococcus can alter its gene-expression as a result of exposure to AMPs and can physiologically increase resistance [48].…”

Lactic acid bacteria protect human intestinal epithelial cells from Staphylococcus aureus and Pseudomonas aeruginosa infections

“…This was confirmed by the results of the CLSM analysis. The cell surface hydrophobicity of microorganisms plays an important role in bacterium-host cell interactions (Swiatlo et al, 2002). Any strategy responsible for reducing the cell surface hydrophobicity and EPS synthesis may affect the development of infection, making the cells more susceptible to antibiotics.…”