Description:
<jats:title>ABSTRACT</jats:title>
<jats:p>
The species
<jats:italic>Campylobacter jejuni</jats:italic>
is naturally competent for DNA uptake; nevertheless, nonnaturally transformable strains do exist. For a subset of strains we previously showed that a periplasmic DNase, encoded by
<jats:italic>dns</jats:italic>
, inhibits natural transformation in
<jats:italic>C. jejuni</jats:italic>
. In the present study, genetic factors coding for DNase activity in the absence of
<jats:italic>dns</jats:italic>
were identified. DNA arrays indicated that nonnaturally transformable
<jats:italic>dns</jats:italic>
-negative strains contain putative DNA/RNA nonspecific endonucleases encoded by CJE0566 and CJE1441 of strain RM1221. These genes are located on
<jats:italic>C. jejuni</jats:italic>
integrated elements 2 and 4. Expression of CJE0566 and CJE1441 from strain RM1221 and a homologous gene from strain 07479 in DNase-negative
<jats:italic>Escherichia coli</jats:italic>
and
<jats:italic>C. jejuni</jats:italic>
strains indicated that these genes code for DNases. Genetic transfer of the genes to a naturally transformable
<jats:italic>C. jejuni</jats:italic>
strain resulted in a decreased efficiency of natural transformation. Modeling suggests that the
<jats:italic>C. jejuni</jats:italic>
DNases belong to the
<jats:italic>Serratia</jats:italic>
nuclease family. Overall, the data indicate that the acquisition of prophage-encoded DNA/RNA nonspecific endonucleases inhibits the natural transformability of
<jats:italic>C. jejuni</jats:italic>
through hydrolysis of DNA.
</jats:p>