The presence of a novel type of surface polysaccharide in Rhizobium meliloti requires a new fatty acid synthase-like gene cluster involved in symbiotic nodule development.
Bacterial exopolysaccharide (EPS) and lipopolysaccharide (LPS) molecules have been shown to play important roles in plant-bacterium interactions. Here we have demonstrated that the fix-23 loci, which compensate for exo mutations during symbiotic nodule development, are involved in the production of a novel polysaccharide that is rich in 3-deoxy-D-manno-2-octulosonic acid (Kdo) but is not the classical LPS. This molecule is likely to be a surface antigen since antiserum to whole Rhizobium meliloti cells reacts strongly with it, and since mutations in fix-23 result in an inability to produce this polysaccharide and to bind bacteriophage 16-3. It is likely that this Kdo-rich polysaccharide is analogous to certain Escherichia coli K-antigens which are anchored to the membrane via a phospholipid moiety. DNA sequence analysis of one gene cluster of this region revealed that the predicted protein products of six genes exhibit a high degree of homology and similar organization to those of the rat fatty acid synthase multifunctional enzyme domains.
Petrovics
G
G
Institute of Genetics, Biological Research Center, Hungarian Academy of Sciences, Szeged.
Putnoky
P
P
Reuhs
B
B
Kim
J
J
Thorp
T A
TA
Noel
K D
KD
Carlson
R W
RW
Kondorosi
A
A
D000595:Amino Acid Sequence; D000818:Animals; D000942:Antigens, Bacterial / Q000276:immunology; D000954:Antigens, Surface / Q000276:immunology; D001483:Base Sequence; D002645:Chickens / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D064429:Fatty Acid Synthases / Q000235:genetics; D005786:Gene Expression Regulation; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics; D005810:Multigene Family; D016366:Open Reading Frames; D009876:Operon; D011135:Polysaccharides, Bacterial / Q000276:immunology / Q000378:metabolism*; D051381:Rats / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D016962:Sinorhizobium meliloti / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D013045:Species Specificity; D013559:Symbiosis / Q000235:genetics*
D000942:Antigens, Bacterial; D000954:Antigens, Surface; D004269:DNA, Bacterial; D009097:Multienzyme Complexes; D011135:Polysaccharides, Bacterial; D064429:Fatty Acid Synthases