Genetic analysis of conservation and variation of lipooligosaccharide expression in two L8-immunotype strains of Neisseria meningitidis

Neisseria meningitidis strains A I and M978 both express the lipooligosacch aride (LOS) L8 immunotype [Gu et al., J. Clin. Microbiol. 30 (1992) 2047-20 53]. Under different growth conditions. strain Al did not change its LOS pr ofile whereas strain M978 produced variable LOS profiles on SDS-PAGE. To un derstand the genetic basis of LOS conservation and variation. their Igt loc us encoding glycosyltransferases responsible for the biosynthesis of the cc -chain of LOS was analyzed. Strain Al possessed only two genes. lgtA and lg tH., at the Igt locus. The lgtA gene was inactivated due to a frameshift mu tation, thus strain Al expressed only L8 LOS. In contrast, strain M978 cont ained five genes lgtZ. lgtC, lgtA. lgtB and lgtE at this locus, thus it had a potential to express L1, L3.7 in addition to the L8 LOS. The data showed that strain Al is a better reference strain for the L8 immunotype because of the stability of L8 LOS expression resulting from its unique Igt locus, In addition. these two strains had two new genetic organizations, lgtAH and lgtZCABE, compared to the reported gene organization at the Igt locus in N . meningitidis. (C) 2001 Federation or European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.