Beschreibung:
<jats:title>ABSTRACT</jats:title>
<jats:p>
Individual bacteria of numerous species can communicate and coordinate their actions via the production, release, and detection of extracellular signaling molecules. In this study, we used the
<jats:italic>Vibrio harveyi</jats:italic>
luminescence bioassay to determine whether
<jats:italic>Helicobacter pylori</jats:italic>
produces such a factor. Cell-free conditioned media from
<jats:italic>H. pylori</jats:italic>
strains 60190 and 26695 each induced >100-fold-greater luminescence in
<jats:italic>V. harveyi</jats:italic>
than did sterile culture medium. The
<jats:italic>H. pylori</jats:italic>
signaling molecule had a molecular mass of <10 kDa, and its activity was unaffected by heating to 80°C for 5 min or protease treatment. The genome sequence of
<jats:italic>H. pylori</jats:italic>
26695 does not contain any gene predicted to encode an acyl homoserine lactone synthase but does contain an orthologue of
<jats:italic>luxS</jats:italic>
, which is required for production of autoinducer-2 (AI-2) in
<jats:italic>V. harveyi</jats:italic>
. To evaluate the role of
<jats:italic>luxS</jats:italic>
in
<jats:italic>H. pylori</jats:italic>
, we constructed
<jats:italic>luxS</jats:italic>
null mutants derived from
<jats:italic>H. pylori</jats:italic>
60190 and 26695. Conditioned media from the wild-type
<jats:italic>H. pylori</jats:italic>
strains induced >100-fold-greater luminescence in the
<jats:italic>V. harveyi</jats:italic>
bioassay than did conditioned medium from either mutant strain. Production of the signaling molecule was restored in an
<jats:italic>H. pylori luxS</jats:italic>
null mutant strain by complementation with a single intact copy of
<jats:italic>luxS</jats:italic>
placed in a heterologous site on the chromosome. In addition,
<jats:italic>Escherichia coli</jats:italic>
DH5α produced autoinducer activity following the introduction of an intact copy of
<jats:italic>luxS</jats:italic>
from
<jats:italic>H. pylori</jats:italic>
. Production of the signaling molecule by
<jats:italic>H. pylori</jats:italic>
was growth phase dependent, with maximal production occurring in the mid-exponential phase of growth. Transcription of
<jats:italic>H. pylori vacA</jats:italic>
also was growth phase dependent, but this phenomenon was not dependent on
<jats:italic>luxS</jats:italic>
activity. These data indicate that
<jats:italic>H. pylori</jats:italic>
produces an extracellular signaling molecule related to AI-2 from
<jats:italic>V. harveyi</jats:italic>
. We speculate that this signaling molecule may play a role in regulating
<jats:italic>H. pylori</jats:italic>
gene expression.
</jats:p>