PMID:19246750

Citation	Lerner, A, Okon, Y and Burdman, S (2009) The wzm gene located on the pRhico plasmid of Azospirillum brasilense Sp7 is involved in lipopolysaccharide synthesis. Microbiology (Reading, Engl.) 155:791-804
Abstract	Several genes involved in the interaction between Azospirillum brasilense Sp7 and plants are located on the pRhico plasmid. Here we report the characterization of an Sp7 mutant strain with impairment of the pRhico-located gene wzm. This gene encodes an inner-membrane component of an ATP-binding cassette (ABC) transporter with similarity to transporters involved in surface polysaccharide export. Indeed, SDS-PAGE revealed that LPS synthesis is affected in the wzm mutant. No significant differences were observed between wild-type and mutant strains in exopolysaccharide (EPS) amount; however, several differences were observed between them in EPS monosaccharide composition, and only wild-type colonies stained positively with Congo red. Microscopy revealed that wzm mutant cells are longer and thinner, and exhibit several differences in their cell surface relative to the wild-type. The wzm mutant was more resistant to oxidative stress, starvation, desiccation, heat and osmotic shock than the wild-type. In contrast, the mutant was more susceptible than the wild-type to UV radiation and saline stress. The strains also differed in their susceptibility to different antibiotics. Differences between the strains were also observed in their outer-membrane protein composition. No differences were observed between strains in their ability to attach to sweet corn roots and seeds, and to promote growth under the tested conditions. As LPS plays an important role in cell envelope structural integrity, we propose that the pleiotropic phenotypic changes observed in the wzm mutant are due to its altered LPS relative to the wild-type.
Links	PubMed Online version:10.1099/mic.0.021824-0
Keywords	ATP-Binding Cassette Transporters/genetics; ATP-Binding Cassette Transporters/metabolism; Azospirillum brasilense/genetics; Azospirillum brasilense/growth & development; Azospirillum brasilense/metabolism; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; DNA, Bacterial/genetics; Genes, Bacterial; Lipopolysaccharides/biosynthesis; Mutation; Oxidative Stress; Plant Roots/microbiology; Plasmids/genetics; Sequence Analysis, DNA; Sodium Chloride/pharmacology; Zea mays/growth & development; Zea mays/microbiology
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
AZOBR:Q6QWB5		GO:0009103: lipopolysaccharide biosynthetic process	ECO:0000315:		P		Fig. 2; in the SDS-PAGE analysis of lipopolysaccharides in the organism, bands corresponding to smooth-LPS and rough-LPS are absent from the wzm mutant.	complete CACAO 4760
AZOBR:Q6QWB5	involved_in	GO:0009103: lipopolysaccharide biosynthetic process	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete

References

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