Affiliation:
1. Division of Biological Sciences and Department of Molecular Microbiology and Immunology, School of Medicine, University of Missouri—Columbia, Columbia, Missouri,1 and
2. The Genome Center, University of Washington, Seattle, Washington2
Abstract
ABSTRACT
The genomes of pathogenic
Haemophilus influenzae
strains are larger than that of Rd KW20 (Rd), the nonpathogenic laboratory strain whose genome has been sequenced. To identify potential virulence genes, we examined genes possessed by Int1, an invasive nonencapsulated isolate from a meningitis patient, but absent from Rd. Int1 was found to have a novel gene termed
lav
, predicted to encode a member of the AIDA-I/VirG/PerT family of virulence-associated autotransporters (ATs). Associated with
lav
are multiple repeats of the tetranucleotide GCAA, implicated in translational phase variation of surface molecules. Laterally acquired by
H. influenzae, lav
is restricted in distribution to a few pathogenic strains, including
H. influenzae
biotype aegyptius and Brazilian purpuric fever isolates. The DNA sequence of
lav
is surprisingly similar to that of a gene previously described for
Neisseria meningitidis
. Sequence comparisons suggest that
lav
was transferred relatively recently from
Haemophilus
to
Neisseria
, shortly before the divergence of
N. meningitidis
and
Neisseria gonorrhoeae
. Segments of
lav
predicted to encode passenger and β-domains differ sharply in G+C base content, supporting the idea that AT genes have evolved by fusing domains which originated in different genomes. Homology and base sequence comparisons suggest that a novel biotype aegyptius AT arose by swapping an unrelated sequence for the passenger domain of
lav
. The unusually mobile
lav
locus joins a growing list of genes transferred from
H. influenzae
to
Neisseria
. Frequent gene exchange suggests a common pool of hypervariable contingency genes and may help to explain the origin of invasiveness in certain respiratory pathogens.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
46 articles.
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