Disruption of Putrescine Biosynthesis in Shewanella oneidensis Enhances Biofilm Cohesiveness and Performance in Cr(VI) Immobilization

<jats:title>ABSTRACT</jats:title> <jats:p> Although biofilm-based bioprocesses have been increasingly used in various applications, the long-term robust and efficient biofilm performance remains one of the main bottlenecks. In this study, we demonstrated that biofilm cohesiveness and performance of <jats:named-content content-type="genus-species">Shewanella oneidensis</jats:named-content> can be enhanced through disrupting putrescine biosynthesis. Through random transposon mutagenesis library screening, one hyperadherent mutant strain, CP2-1-S1, exhibiting an enhanced capability in biofilm formation, was obtained. Comparative analysis of the performance of biofilms formed by <jats:named-content content-type="genus-species">S. oneidensis</jats:named-content> MR-1 wild type (WT) and CP2-1-S1 in removing dichromate (Cr <jats:sub>2</jats:sub> O <jats:sub>7</jats:sub> <jats:sup>2−</jats:sup> ), i.e., Cr(VI), from the aqueous phase showed that, compared with the WT biofilms, CP2-1-S1 biofilms displayed a substantially lower rate of cell detachment upon exposure to Cr(VI), suggesting a higher cohesiveness of the mutant biofilms. In addition, the amount of Cr(III) immobilized by CP2-1-S1 biofilms was much larger, indicating an enhanced performance in Cr(VI) bioremediation. We further showed that <jats:italic>speF</jats:italic> , a putrescine biosynthesis gene, was disrupted in CP2-1-S1 and that the biofilm phenotypes could be restored by both genetic and chemical complementations. Our results also demonstrated an important role of putrescine in mediating matrix disassembly in <jats:named-content content-type="genus-species">S. oneidensis</jats:named-content> biofilms. </jats:p>