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Five new genes are important for common polysaccharide antigen biosynthesis in Pseudomonas aeruginosa.

ABSTRACT:

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Common polysaccharide antigen (CPA) is a conserved cell surface polysaccharide produced by Pseudomonas aeruginosa. It contains a rhamnan homopolymer and is one of the two forms of O polysaccharide attached to P. aeruginosa lipopolysaccharide (LPS). Our laboratory has previously characterized an eight-gene cluster (pa5447-pa5454 in P. aeruginosa PAO1) required for biosynthesis of CPA. Here we demonstrate that an adjacent five-gene cluster pa5455-pa5459 is also involved. Using reverse transcriptase PCR (RT-PCR), we showed that the original eight-gene cluster and the new five-gene cluster are both organized as operons. We have analyzed the LPS phenotypes of in-frame deletion mutants made in each of the five genes, and the results verified that these five genes are indeed required for CPA biosynthesis, extending the CPA biosynthesis locus to contain 13 contiguous genes. By performing overexpression experiments of different sets of these biosynthesis genes, we were able to obtain information about their possible functions in CPA biosynthesis.

Importance

Lipopolysaccharide (LPS) is an important cell surface structure of Gram-negative bacteria. The human opportunistic pathogen Pseudomonas aeruginosa simultaneously produces an O-antigen-specific (OSA) form and a common polysaccharide antigen (CPA) form of LPS. CPA, the focus of this study, is composed of ?-1-2, ?1-3-linked d-rhamnose sugars and has been shown to be important for attachment of the bacteria to human airway epithelial cells. Genome sequencing of this species revealed a new five-gene cluster that we predicted to be involved in CPA biosynthesis and modification. In this study, we have generated chromosomal knockouts by performing in-frame deletions and allelic replacements. Characterizing the function of each of the five genes is important for us to better understand CPA biosynthesis and the mechanisms of chain length termination and regulation of this unique D-rhamnan polysaccharide.

SUBMITTER: Hao Y

PROVIDER: S-EPMC3560663 | biostudies-literature | 2013 Jan

REPOSITORIES: biostudies-literature

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Five new genes are important for common polysaccharide antigen biosynthesis in Pseudomonas aeruginosa.

Hao Youai Y King Jerry D JD Huszczynski Steven S Kocíncová Dana D Lam Joseph S JS

mBio 20130122 1

<h4>Unlabelled</h4>Common polysaccharide antigen (CPA) is a conserved cell surface polysaccharide produced by Pseudomonas aeruginosa. It contains a rhamnan homopolymer and is one of the two forms of O polysaccharide attached to P. aeruginosa lipopolysaccharide (LPS). Our laboratory has previously characterized an eight-gene cluster (pa5447-pa5454 in P. aeruginosa PAO1) required for biosynthesis of CPA. Here we demonstrate that an adjacent five-gene cluster pa5455-pa5459 is also involved. Using r ...[more]

PMID: 23341552

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Project description:The outer leaflet of the outer membrane of nearly all Gram-negative bacteria contains lipopolysaccharide (LPS). The distal end of LPS may be capped with O antigen, a long polysaccharide that can range from a few to hundreds of sugars in length. The chain length of the polysaccharide has many implications for bacterial survival and consequently is tightly controlled. In the Wzx/Wzy-dependent route of O antigen synthesis, one or more Wzz proteins determine the chain length via an unknown mechanism. To gain insight into this mechanism, we identified and characterized important regions of two Wzz proteins in Pseudomonas aeruginosa serotype O13, which confer the production of "long" (Wzz1) and "very long" (Wzz2) chain lengths, respectively. We found that compared to Wzz1, Wzz2 has distinct amino acid insertions in the central α-helices (insα6 and insα7) and in membrane-distal (insL4) and -proximal (insIL) loops. When these regions were deleted in Wzz2, the mutant proteins conferred drastically shortened chain lengths. Within these regions we identified several conserved amino acid residues that were then targeted for site-directed mutagenesis. Our results implicate an RTE motif in loop 4 and a "hot spot" of charged and polar residues in insα7 in the function of Wzz2 We present evidence that the functionally important residues of insα7 are likely involved in stabilizing Wzz through coiled-coil interactions.IMPORTANCE O antigen is an important virulence factor presented on the cell surface of Gram-negative bacteria that is critical for bacterial physiology and pathogenesis. However, some aspects of O antigen biosynthesis, such as the mechanisms for determining polysaccharide chain length, are poorly understood. In this study, we identified unique regions in the O antigen chain length regulators (termed Wzz) of the problematic opportunistic pathogen Pseudomonas aeruginosa We show that these regions are critical for determining O antigen chain length, which provides new insight into the model of the Wzz mechanism. Ultimately, our work adds knowledge toward understanding an important step in the biosynthesis of this virulence factor, which is applicable to a wide range of Gram-negative pathogens.

Dataset Information

Five new genes are important for common polysaccharide antigen biosynthesis in Pseudomonas aeruginosa.

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Importance

Publications

Five new genes are important for common polysaccharide antigen biosynthesis in Pseudomonas aeruginosa.

Similar Datasets

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