Brucellosis 2003 proceedings - PHIDIAS

Poster Session
apparent differences a phylogenetic analysis was undertaken on twenty-two
reference and thirty-five marine mammal Brucella strains to derive an hypothesis of
the evolution of the genus and form the basis of an appropriate taxonomic
classification of marine Brucella species. Strains compared in the phylogenetic
analysis included isolates from pinniped and cetacean species gathered from
European and North American coastal locations. Results of the phylogenetic
reconstruction suggest that marine isolates are a diverse group forming distinct
clades that closely follow their host specificity and their geographic distribution.
European strains isolated from pinnipediae and cetaceae appear to be host specific
i.e. a monophyletic clade of pinniped strains and a monophyletic clade of cetacean
strains. North American strains isolated from pinnipediae species form a separate
monophyletic clade to the European strains. The nestedness of the phylogenetic
reconstruction indicate that although pinniped and cetacean strains form distinct
groups these results indicate that each species is further differentiated by their
geographic location. The results of this study should be considered when making
decisions on the taxonomic classification of Brucella strains isolated from marine
mammal species.
116- THE Brucella melitensis FLAGELLAR GENES ARE NOT CRYPTIC.
D. Fretin, S. Leonard, P. Lestrate, R.-M. Delrue, J.-J. Letesson and A. Tibor. URBM, Facultés
Universitaires Notre-Dame de la Paix, rue de Bruxelles 61, B-5000 Namur, Belgium.
Even though brucellae are described as non motile, the Brucella genome
contains three clusters of flagellar genes on the small chromosome. We identified all
the strutural genes for building a flagellum as well as for its rotation however no gene
for chemotactic receptors or transducers were detected. The major part of the 3
clusters showed a clear syntheny with other Rhizobiaceae. Several coding
sequences typical of α-Proteobacteria flagellar systems are also present.
The following results demonstrate that Brucella flagellar genes are not cryptic.
An STM screen of B. melitensis mutants in mice identified a mutant in the fliF gene
encoding the flagellar MS ring homologue. The fliF promoter is specifically induced
intracellularly. The genes fliF, flgE and fliC are expressed in vitro. The presence of
fliF is necessary for FlgE and FliC expression indicating the existence of a flagellar
regulon in Brucella. Mutants in coding sequences typical of flagellar systems (motB,
flgI, flgE and fliC) are attenuated in BALB/c mice.
117- Brucella LIPIDS: CHARACTERIZATION OF pmtA, A GENE ENCODING A
PHOSPHATIDYL-ETAHNOLAMINE-N-METHYLTRANSFERASE INVOLVED IN
PHOSPHATIDYL-CHOLINE SYNTHESIS.
R. Conde-Álvarez, I. Moriyón and M. Iriarte. Departamento de Microbiología, Universidad de Navarra,
Pamplona, Spain.
Brucella cell envelopes are rich in phosphatidyl-choline, a phospholipid
unusual in gram-negative pathogens. A search in the complete genomic sequence of
Brucella melitensis 16M revealed a ORF (BMEI2000) putatively coding for a
phosphatidyl-ethanolamine-N-methyltransferase (PmtA) with homologous in other
members of the α-Proteobacteria. Analysis of the DNA region showed that
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Brucellosis 2003 International Research Conference