The circular pVir plasmid of Campylobacter jejuni strain 81-176 was determined to be 37,468 nucleotides in length with a G؉C content of 26%. A total of 83% of the plasmid represented coding information, and all but 2 of the 54 predicted open reading frames were encoded on the same DNA strand. There were seven genes on the plasmid in a continguous region of 8.9 kb that encoded orthologs of type IV secretion proteins found in Helicobacter pylori, including four that have been described previously

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In this article, we report on the nucleotide sequences of the rol genes ofEscherichia coil 075

We report on the cloning and characterization of the rJb gene cluster of the 075 lipopolysaccharide from a urinary tract isolate of Escherichia coli. Deletion cloning defined the minimum region of DNA that expressed the 075 antigen in E. coli host strains to be on a 12.4-kb insert. However, the E. coli strain expressing this region did not produce a polymerized 0 chain as detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and silver staining. A slightly larger DNA clone of 13.4 kb produced a polymerized 0 chain in E. coli S0874 but was found to be abnormal in its distribution over the surface membrane. Normal wild-type E. coli, as with Salmonella spp., has a bimodal distribution of the lipopolysaccharide on the surface which is seen as an abundance of long and short 0 chains attached to the lipid A-core structure. We found in a region adjacent to the cloned rib region, and on the opposite side from where the putative polymerase (rfc) is encoded, a novel protein of 35.5 kDa expressed from a 1.75-kb DNA fragment. This protein was shown to complement in trans the E. coli strains carrying plasmids that expressed abnormal, unregulated lipopolysaccharides. The expression of these complemented strains was bimodal in distribution. Mutation of the gene encoding this protein destroyed its ability to regulate 0-chain distribution. We propose to call this regulator gene rol, for regulator of 0 length.The lipopolysaccharide (LPS) antigen of Escherichia coli and Salmonella spp. consists of three different molecular species (lipid A, core oligosaccharide, and 0 polysaccharide) that are synthesized independently of each other and are ligated together in or on the inner membrane (17). The O-polysaccharide subunit typically consists of one to five sugar molecules linked together to form a macromolecular polymer of repeated units that vary from 1 to more than 40 in number (11). After assembly, the entire LPS molecule is translocated to the outer membrane by an unknown mechanism (11, 15). The lipid A and core units are embedded in the outer membrane, while the 0 antigen extends outward from the cell. The 0 antigen has been shown to be important in mediating the effects of serum resistance, infection by certain bacteriophages, and interaction with the microenvironment (4,20,22,25). The presence of 0 antigen on the surface of these bacteria confers a smooth phenotype and has been correlated to increased virulence (18).On sodium dodecyl sulfate (SDS)-polyacrylamide gels, silver-stained or radiolabeled LPS has a ladderlike appearance, with each rung or step of the ladder corresponding to a complete lipid A-core unit plus an 0 chain of a specific length. Several groups of investigators have noted a bimodal distribution of LPS from wild-type strains in stained SDSpolyacrylamide gels (3, 10, 21). High-molecular-weight 0 antigens with chain lengths of 19 to 34 make up to 77% of the total antigen, with low-molecular-weight 0 antigen (1 to 5 chain lengths) forming the bulk of the remainder. Intermediate sizes of 0 antigen ...

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