Membrane vesicle formation is associated with pyocin production under denitrifying conditions in <i> <scp>P</scp> seudomonas aeruginosa </i>   <scp>PAO</scp> 1

<jats:title>Summary</jats:title> <jats:p> Many <jats:styled-content style="fixed-case">G</jats:styled-content> ram‐negative bacteria produce membrane vesicles ( <jats:styled-content style="fixed-case">MVs</jats:styled-content> ) that serve as vehicles to mediate intraspecies and interspecies interactions. Despite their ubiquity in <jats:styled-content style="fixed-case">G</jats:styled-content> ram‐negative bacteria and their biological importance, how <jats:styled-content style="fixed-case">MV</jats:styled-content> formation is regulated is poorly understood. <jats:italic> <jats:styled-content style="fixed-case">P</jats:styled-content> seudomonas aeruginosa </jats:italic> is a ubiquitous bacterium that is one of the most extensively studied model organism in <jats:styled-content style="fixed-case">MVs</jats:styled-content> . Recent studies highlight the importance of a quorum‐sensing signal, <jats:italic> <jats:styled-content style="fixed-case">P</jats:styled-content> seudomonas </jats:italic> quinolone signal ( <jats:styled-content style="fixed-case">PQS</jats:styled-content> ), in the formation of <jats:styled-content style="fixed-case">MVs</jats:styled-content> ; however, <jats:styled-content style="fixed-case">PQS</jats:styled-content> synthesis requires oxygen and is not produced under anoxic conditions. This situation leads to the question of <jats:styled-content style="fixed-case">MV</jats:styled-content> production under anoxic conditions. Here, we examined whether <jats:styled-content style="fixed-case">MVs</jats:styled-content> are produced under denitrifying conditions and what kind of factors are involved in the <jats:styled-content style="fixed-case">MV</jats:styled-content> production under such condition. Under denitrifying condition, <jats:italic> <jats:styled-content style="fixed-case">P</jats:styled-content> . aeruginosa </jats:italic>   <jats:styled-content style="fixed-case">PAO</jats:styled-content> 1 produced a considerable amount of <jats:styled-content style="fixed-case">MVs</jats:styled-content> . Interestingly, pyocin components were found to be accumulated in the isolated <jats:styled-content style="fixed-case">MVs</jats:styled-content> . Pyocin‐related protein mutants produced less <jats:styled-content style="fixed-case">MVs</jats:styled-content> compared with the wild type. We further indicate that pyocin production is activated by nitric oxide, in which the <jats:styled-content style="fixed-case">SOS</jats:styled-content> response is involved. This study presents a regulatory mechanism where pyocin is associated with <jats:styled-content style="fixed-case">MV</jats:styled-content> production, and further implies how the environment impacts <jats:styled-content style="fixed-case">MV</jats:styled-content> production in <jats:italic> <jats:styled-content style="fixed-case">P</jats:styled-content> . aeruginosa </jats:italic> . </jats:p>