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American Society for Biochemistry and Molecular Biology

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Journal of Biological Chemistry

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Lipopolysaccharide (LPS) is a major component of the bacterial outer membrane, and for Rhizobium spp. has been shown to play a critical role in the establishment of an effective nitrogen-fixing symbiosis with a legume host. Many genes required for O-chain polysaccharide synthesis are in the lps α region of the CE3 genome; this region may also carry lps genes required for core oligosaccharide synthesis. The LPSs from several strains mutated in the α region were isolated, and their mild acid released oligosaccharides, purified by high performance anion-exchange chromatography, were characterized by electrospray- and fast atom bombardment-mass spectrometry, NMR, and methylation analysis. The LPSs from several mutants contained truncated O-chains, and the core region consisted of a (3-deoxy-D-manno-2-octulosomic acid) (Kdo)-(26)-α-Galp-(16)-[α-GalpA-(14)]-α-Manp-(15)-Kdop (3-deoxy-D-manno-2-octulosomic acid) (Kdo)pentasaccharide and a α-GalpA-(14)-[α-GalpA-(15)]-Kdop trisaccharide. The pentasaccharide was altered in two mutants in that it was missing either the terminal Kdo or the GalA residue. These results indicate that the lps α region, in addition to having the genes for O-chain synthesis, contains genes required for the transfer of these 2 residues to the core region. Also, the results show that an LPS with a complete core but lacking an O-chain polysaccharide is not sufficient for an effective symbiosis.


This research was originally published in Journal of Biological Chemistry, Vol. 270, No. 20 (May 1995): 11783-11788. DOI. © 1995 the American Society for Biochemistry and Molecular Biology. Used with permission.

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