Regulation of O antigen Chain Length in Pseudomonas aeruginosa

Lipopolysaccharide (LPS) is an important component of a Gram-negative bacterium's outer membrane. LPS is composed of lipid A, a core oligosaccharide and the O antigen side chain. The O antigen side chain is composed of repeating sugar subunits and extends out from the surface of the cell. P. aeruginosa produces a bi-modal distribution of two preferred O antigen chain lengths, referred to as long and very long. The length of the side chain is determined by the Wzz proteins; P. aeruginoa encodes two Wzz proteins to produce each preferred chain length. Wzz1, associated with the O antigen locus, produces the long chain length while Wzz2, located elsewhere in the genome, makes the very long chain length. These studies were performed to better understand the role each of these chain lengths plays during the infectious process. Using wzz mutants in a pneumonia mouse model of infection, it was determined that the long chain length is more important for virulence compared to the very long chain length. The amount of these preferred chain lengths changes when P. aeruginosa is exposed to different conditions, so the regulation of the wzz genes was investigated. The promoters for each wzz gene were determined and their activity tested. The regulation of the wzz2 gene was found to correlate with the amount of the very long chain length when P. aeruginosa was grown at different temperatures while wzz1 was consistently expressed under the conditions investigated. Finally, the activity of the Wzz2 protein was explored. Despite the importance of achieving proper chain length for the survival of the bacterium, how the Wzz proteins regulate length has not been determined. These proteins are located in the inner membrane and the monomers come together to form an oligomer composed of five to  nine proteins. By comparing the sequences of two serotype O11 Wzz2 proteins that iii produce different very long chain lengths, it was determined that the interaction between monomers is crucial for oligomer stability and thus influences the chain length produced.

Note: Abstract extracted from PDF text