Legionella oakridgensis ATCC 33761 genome sequence and phenotypic characterization reveals its replication capacity in amoebae

Abstract

Legionella oakridgensis is able to cause Legionnaires` disease, but is less virulent compared to L. pneumophila strains and very rarely associated with human disease. L. oakridgensis is the only species of the family legionellae which is able to grow on media without additional cysteine. In contrast to earlier publications, we found that L. oakridgensis is able to multiply in amoebae. We sequenced the genome of L. oakridgensis type strain OR-10 (ATCC 33761).The genome is smaller than the other yet sequenced Legionella genomes and has a higher G+C-content of 40.9%. L. oakridgensis lacks a flagellum and it also lacks all genes of the flagellar regulon except of the alternative sigma-28 factor FliA and the anti-sigma-28 factor

Growth-related Metabolism of the Carbon Storage Poly-3-hydroxybutyrate in Legionella pneumophila

“…Indeed, host cell glycogen could be degraded to glucose by the action of the bacterial glucoamylase GamA (19,34). Further supporting the role of glucose as a nutrient for intracellular L. pneumophila, glucose uptake was found to be increased during the late phases of growth (33), and Legionella species-specific differences in their usages of glucose and serine as carbon substrates were suggested recently (35,36). However, the differential transfer of substrates during the different growth phases of L. pneumophila has not yet been directly shown.…”

Functional Analysis of the Alternative Sigma-28 Factor FliA and Its Anti-Sigma Factor FlgM of the Nonflagellated Legionella Species L. oakridgensis

“…Recently, two human cases of Legionnaires' disease caused by L. oakridgensis were reported in France (3), showing that the bacteria are able to replicate inside human cells (1,(4)(5)(6)(7). Moreover, it was demonstrated that L. oakridgensis is able to multiply inside amoebae (4) and that the type IV secretion system is a key virulence factor; new virulence factors were also described (4).…”

“…Moreover, it was demonstrated that L. oakridgensis is able to multiply inside amoebae (4) and that the type IV secretion system is a key virulence factor; new virulence factors were also described (4). In general, no additional cysteine is needed to grow L. oakridgensis on agar plates and extracel-lular glucose cannot be metabolized by the bacterium (4). For L. oakridgensis, it was demonstrated that the species is nonflagellated and that almost all flagellar regulon genes are absent, including the master regulator protein FleQ.…”

“…For L. oakridgensis, it was demonstrated that the species is nonflagellated and that almost all flagellar regulon genes are absent, including the master regulator protein FleQ. Nevertheless, the putative alternative sigma-28 factor FliA and the putative anti-sigma-28 factor FlgM are still present (4,8). In a closely related nonflagellated species, Legionella longbeachae, FliA, FleN, and FlgM, as well as FleQ, FleSR, and FlgD, are still present, whereas the other flagellar regulon genes are absent.…”

“…Interestingly, flagellated L. pneumophila strains are motile but do not harbor chemotaxis genes and do not show chemotaxis (9). Moreover, nonflagellated, nonmotile L. longbeachae species lack almost all genes of the flagellar regulon but have been shown to have a chemotaxis operon, and L. oakridgensis is negative for the flagellar regulon and the chemotaxis-encoding genes (4,10,11). In general, chemotaxis enables bacteria to locate special environmental conditions and get closer to higher concentrations of attractants (12)(13)(14).…”