Structure Elucidation of the O-Antigen of Salmonella enterica O51 and Its Structural and Genetic Relation to the O-Antigen of Escherichia coli O23*

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A. V. Perepelov^1#**, Bin Liu^2,3#, Dan Guo^2,3, S. N. Senchenkova¹, A. S. Shahskov¹, Lu Feng^2,3, Lei Wang^2,3, and Y. A. Knirel¹

¹Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky pr. 47, 119991 Moscow, Russia; fax: (499) 137-6148; E-mail: perepel@ioc.ac.ru

²TEDA School of Biological Sciences and Biotechnology, Nankai University, TEDA, Tianjin 300457, P. R. China

³Tianjin Key Laboratory for Microbial Functional Genomics, TEDA College, Nankai University, TEDA, Tianjin 300457, P. R. China; E-mail: striker198126@yahoo.com.cn

^* This paper is based on a presentation made at the 4th Baltic Conference on Microbial Carbohydrates, Hyytiala Forestry Field Station, Finland, September 19-22, 2010.

^# These authors contributed equally to this work.

^** To whom correspondence should be addressed.

Received December 24, 2010; Revision received February 3, 2011

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The O-polysaccharide (O-antigen) of Salmonella enterica O51 was isolated by mild acid degradation of the lipopolysaccharide and its structure was established using sugar analysis and NMR spectroscopy. The O-antigen of Escherichia coli O23, whose structure was elucidated earlier, possesses a similar structure and differs only in the presence of an additional lateral α-D-Glcp residue at position 6 of the GlcNAc residue in the main chain. Sequencing of the O-antigen gene clusters of S. enterica O51 and E. coli O23 revealed the same genes with a high-level similarity. By comparison with opened gene databases, all genes expected for the synthesis of the common structure of the two O-antigens were assigned functions. It is suggested that the gene clusters of both bacteria originated from a common ancestor, whereas the O-antigen modification in E. coli O23, which, most probably, is induced by prophage genes outside the gene cluster, could be introduced after the species divergence.

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KEY WORDS: Salmonella enterica, Escherichia coli, lipopolysaccharide, bacterial polysaccharide, structure, gene cluster, O-antigen

DOI: 10.1134/S0006297911070078

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