Structure elucidation and gene cluster annotation of the O-antigen of Halomonas titanicae TAT1 containing three residues of 2,3-diacetamido-2,3-dideoxy-D-glucuronic acid

A halotolerant hydrocarbon-oxidizing bacterium Halomonas titanicae strain TAT1 was isolated from a petroleum reservoir. The O-polysaccharide (O-antigen) was isolated from the lipopolysaccharide of H. titanicae TAT1 and studied by component analyses and 1D and 2D NMR spectroscopy. The following structure of the repeating linear pentasaccharide O-unit, containing only aminosugars, was established: -> 4)-beta-D-GlcpNAc3NAcA-(1 -> 4)-beta-D- GlcpNAc3NAcA-(1 -> 6)-alpha-D-GlcpNAc-(1 -> 4)-beta-D-GlcpNAc3NAcA-(1 -> 6)-alpha-D-GlcpNAc-(->, where D-GlcNAc3-NAcA indicates 2,3-diacetamido-2,3-dideoxy-D-glucuronic acid. The O-antigen gene cluster was identified in the genome of H. titanicae TAT1 and compared with available database sequences. The genes revealed in the O -antigen gene cluster and the assigned functions of putative proteins were consistent with the established poly-saccharide structure.

Automated summary

In this study, a halotolerant hydrocarbon-oxidizing bacterium Halomonas titanicae TAT1 strain was isolated from a petroleum reservoir, and the O-polysaccharide structure and gene cluster were successfully identified. The O-antigen structure was found to be consistent with the genes in the O-antigen gene cluster of the H. titanicae TAT1 genome.