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The article offers information on the effect of undecaprenyl phosphate (Und-P) recycling in an Escherichia coli undecaprenyl-pyrophosphate phosphatase. Und-P is a glycan biosynthetic intermediates lipid carrier for carbohydrate polymers which are exported to the bacterial cell envelope. It arises from the undecaprenyl pyrophosphate's dephosphorylation, molecules produced through "de novo" synthesis and from released undecaprenyl pyrophosphate's recycling after the glycan component were transferred to other acceptor molecules.

One of the most common pathways for the export of O-specific lipopolysaccharide (LPS) across the plasma membrane requires the participation of the Wzx protein. Wzx belongs to a family of integral membrane proteins that share little conservation in their primary amino acid sequence, making it difficult to delineate functional domains. This paper reports the cloning and expression in Escherichia coil K-12 of various Wzx homologues from different bacteria as FLAG epitope-tagged protein fusions. A reconstitution system for O16 LPS synthesis was used to assess the ability of each Wzx protein to complement an E. coil K-1 2 Δwzx mutant. The results demonstrate that Wzx proteins from O-antigen systems that use N-acetylglucosamine or N-acetylgalactosamine for the initiation of the biosynthesis of the O repeat can fully complement the formation of O16 LPS. Partial complementation was seen with Wzx from Pseudomonas aeruginosa, a system that uses N-acetylfucosamine in the initiation reaction. In contrast, there was negligible complementation with the Wzx protein from Salmonella enterica, a system in which galactose is the initiating sugar. These results support a model whereby the first sugar of the O repeat can be recognized by the O-antigen translocation machinery. [ABSTRACT FROM AUTHOR]

Analyzes the genetic organization of the O7-specific lipopolysaccharide (LPS) biosynthesis cluster of Escherichia coli VW187. LPS as a component of the bacterial outer membrane; Role of O antigen in the antigenic variability of the cell surface and virulence bacteria; Development of a set of primers for detection of O7-specific sequences.

Studies intracellular survival and saprophytic growth of isolates from the Burkholderia cepacia complex in free-living amoeba. Localization of intracellular B. cepacia CEP021 organisms in vacuoles; Host-dependency and variation with the temperature of incubation of amoeba infection; Kinetics of intracellular growth of B. cepacia.

The article investigated the contribution of the distinct functional area of Salmonella enterica WbaP transferase. WbaP refers to a membrane enzyme which starts the O antigen synthesis in Salmonella through catalysing the shift of galactose 1-phosphate onto undecaprenyl phosphate. Its three structural domains which include large central periplasmic loop, N-terminal region with four transmembrane helices and C-terminal domain with last transmembrane helix and cytoplasmic tail have been examined to determine their importance on WbaP function. The result shows that N-terminal region is needed for the stability of protein in bacterial membrane.

The article presents a study on the effect of varying the relative expression levels of the genes wzzB, wzzpHS-2 and wzy on O antigen polysaccharide chain length distribution in Shigella flexneri 2a. It states that the genes were cloned under the control of arabinose- and rhamnose-inducible promoters. Furthermore, no direct interaction between Wzy and WzzB was found, which suggests that they may not interact physically but by other means such as translocated O antigen precursors.

The article presents a study on the O-antigen modal chain length in Shigella flexneri 2a as a growth-regulated RfaH-mediated transcriptional control of the wzy gene. This paper focuses on the production of lipopolysaccharide (LPS) with O-antigen chain lengths. The short OAg controlled WzzB and long OAg is determined by WzzpHS-2. It demonstrates the synthesis and regulation of length distribution of S. flexneri OAg under growth-phase-dependent. Quantitative electrophoretic analysis is observed along with the increased growth and distribution. The conclusion showed the expression of wzy, wzzB and wzzpHS-2 genes.

The authors previously reported increased expression of the Salmonella enterica serovar Typhi (S. typhi) rfaH gene when the bacterial cells reach stationary phase. In this study, using a lacZ fusion to the rfaH promoter region, they demonstrate that growth-dependent regulation of rfaH expression occurs at the level of transcription initiation. It was also observed that production of the lipopolysaccharide (LPS) O-antigen by S. typhi Ty2 correlated with the differential expression of rfaH during bacterial growth. This was probably due to the increased cellular levels of RfaH, since expression of the distal gene in the O-antigen gene cluster of S. typhi Ty2, wbaP, was also increased during stationary growth, as demonstrated by RT-PCR analysis. Examination of the sequences upstream of the rfaH coding region revealed homologies to potential binding sites for the RcsB/RcsA dimer of the RcsC/YopJ/RcsB phosphorelay regulatory system and for the RpoN alternative sigma factor. The expression of the rfaH gene in rpoN and rcsB mutants of S. typhi Ty2 was measured. The results indicate that inactivation of rpoN, but not of rcsB, suppresses the growth-phase-dependent induction of rfaH expression. Furthermore, production of β-galactosidase mediated by the rfaH-lacZ fusion increased approximately fourfold when bacteria were grown in a nitrogenlimited medium. Nitrogen limitation was also shown to increase the expression of the O-antigen by the wild-type S. typhi Ty2, as demonstrated by a similar electrophoretic profile to that observed during the stationary phase of growth in rich media. It is therefore concluded that the relationship between LPS production and nitrogen limitation parallels the pattern of rfaH regulation under the control of RpoN and is consistent with the idea that RpoN modulates LPS formation via its effect on rfaH gene expression during bacterial growth. [ABSTRACT FROM AUTHOR]