Serogroup specificity of Legionella pneumophila is related to lipopolysaccharide characteristics

Abstract

We studied the lipopolysaccharide (LPS) of LegioneUa pneumophila and six other Legionella species to determine whether strain differences were apparent. The LPS was purified by a cold ethanol extraction procedure, and total carbohydrates represented 10 to 20% of LPS weight. 2-keto-3-deoxyoctonate represented 1 to 13% of the total carbohydrate present in the LPS. By sodium dodecyl sulfate-polyacrylamide gel electrophoresis, all strains except L. dumoffi showed smooth-type LPS with multiple high-molecular-weight complexes. Proteinase K-treated, whole-cell lysates showed profiles similar to those of purified LPS. Each serogroup of L. pneumophila and each Legionella species had a distinct sodium dodecyl sulfate-polyacrylamide gel electrophoresis profile. L. pneumophila lipid A is antigenically related to the lipid A of Enterobacteriaceae. In immnunoblot assays with the LPS of L. pneumophila serogroups 1 to 6 as antigens, serogroup-specific immune monkey sera recognized homologous purified LPS, but not the LPS of the five heterologous serogroups. These studies indicate that LOS composition may be a determinant of serogroup specificity as defined by the immunofluorescence-based serogrouping schema for L. pneumophila and other Legionella species.

The structure of the O‐specific chain of Legionella pneumophila serogroup 1 lipopolysaccharide

“…Although lipopolysaccharide obtained by this modification [5] still contains small amounts of protein (3-5%, by mass, of lipopolysaccharide), it is considered most useful as it was the only one-step procedure to give acceptable lipopolysaccharide yields (4.5%, by mass, of bacteria). SDSIPAGE (14%) analysis of lipopolysaccharide obtained by various extraction procedures and modifications thereof [20,21,231 revealed no difference in the characteristic short-band spacing, indicating structural similarity or identity between the different lipopolysaccharide preparations. In addition, the lipopolysaccharide of L. pneumophila serogroup 1 extracted by the modified phenokhloroford petroleum ether procedure [5] exhibited the same qualitative and quantitative sugar composition (Rha, GlcN, Man, QuiN, Kdo ; data not shown) as lipopolysaccharide preparations obtained with other extraction methods [17, 20, 21, 26, 301. Although SDS/PAGE suggests the presence of smooth (S-form) lipopolysaccharide, the banding pattern of serogroup 1 is different from that of Enterobacteriaceae such as S. minnesota or E. coli.…”

“…E. coli or Salmonella spp. ), L. pneumophila lipopolysaccharide could not be isolated from the water phase but, instead, was identified in the phenol phase [21,23,25,27, 281 indicating a different physicochemical behaviour, i.e. an increased hydrophobicity.…”

“…Previous chemical analyses of L. pneurnophila lipopolysaccharide 117-221 have been carried out in several laboratories, some studies including serological investigations with polyclonal [20,21,231 and monoclonal antibodies [17,22,241. So far, however, the structure of the 0-specific chain and the serological determinants of Legionella lipopolysaccharide have not been elucidated [20, 21, 251. In the present study we describe for the first time the complete chemical analysis and structure of the 0-chain of Legionella pneumophila Philadelphia strain 1 (serogroup 1) lipopolysaccharide as a 5,7-diamino-3,5,7,9-tetradeoxy-~-glycero-~-galacto-nonulosonic acid homopolymer.…”

“…Different lipopolysaccharide extraction procedures described in the literature have raised divergent results with respect to the yield (0.04-4.4% by mass) [21] depending on the Legionella serogroup and the extraction procedure used [17]. In contrast to other Gram-negative bacteria (e.g.…”

Differential nitric oxide (NO) production by macrophages from mice and guinea pigs infected with virulent and avirulent Legionella pneumophila serogroup 1

“…One such antibody is directed against an antigenic determinant of Leg. pneumophila LPS [31], suggesting that the differences in LPS [32], a major component of the bacterial cell wall, could explain the differences in NO synthase activity in macrophages.…”