Lipopolysaccharide (LPS) is the major component of the outer leaflet of the outer membrane of Gram-negative bacteria. The LPS molecule is composed of two biosynthetic entities: the lipid A - core and the O-polysaccharide (O-antigen). Most biological effects of LPS are due to the lipid A part, however, there is an increasing body of evidence indicating that O-antigen (O-ag) plays an important role in effective colonization of host tissues, resistance to complement-mediated killing and in the resistance to cationic antimicrobial peptides that are key elements of the innate immune system.

Recently, data has started to accumulate on the intricacies in the genetic regulation of the structural components of this molecule and this is highly relevant to the biological function of the molecule.

from Skurnik M and Bengoechea JA in Bacterial Polysaccharides: Current Innovations and Future Trends (2009) Ullrich M (Ed) Published by Caister Academic Press

Further reading: Bacterial Polysaccharides

Labels: gram negative bacteria, lipopolysaccharide, LPS, pathogenesis, polysaccharides, regulation

Bacteria assemble a variety of structures on their cell surface, including extended fibers generally termed pili or fimbriae. These pili mediate interactions with other bacteria, the host, and the environment.

Pili often function as adhesins, dictating specific binding to and colonization of biological as well as non-biological surfaces. Pili are critical virulence factors for pathogenic bacteria, initiating infection and determining how and where bacterial colonization may occur. A variety of different classes of pili are found in prokaryotes. Pili have a diverse array of functions. Pili are essential for host colonization, virulence and pathogenesis for many bacteria and, in the case of type IV pili, can also be employed for motility across solid surfaces.

Further reading:

1. Pili and Flagella
2. Bacterial Secreted Proteins
3. Microbiology Books

Labels: adhesins, colonization, fimbriae, flagella, motility, pathogenesis, pathogenic, pili, type IV pili, virulence