A novel family of nonribosomal peptides modulate collective behavior in Pseudovibrio bacteria isolated from marine sponges

Collective behavior is a common feature of life. Although swarming motility and biofilms are opposed collective behaviors, both contribute to bacterial survival and host colonization. We have identified a link between motility/biofilms and a nonribosomal peptide synthetase-polyketide synthase gene cluster family (ppp) conserved in Pseudovibrio and Pseudomonas Proteobacteria known to interact with diverse eukaryotes. After developing reverse genetics for Pseudovibrio, we discovered two pseudovibriamide families, heptapeptides with a reversal in chain polarity via an ureido linkage 1-6 and related nonadepsipeptides 7-12. Imaging mass spectrometry showed that 1 was excreted whereas 7 was colony-associated. Deletion of pppA abolished production of 1-12 leading to reduced motility and increased biofilm production. pppD mutants that produced only 1-6 showed motility comparable to the wild-type and reduced biofilm formation, indicating that the excreted heptapeptides play a role in promoting motility. In contrast to lipopeptides widely known to affect swarming and biofilms, pseudovibriamides are not surfactants. Our results expand current knowledge on metabolites mediating bacterial collective behavior. Moreover, the establishment of reverse genetics will enable future exploration of the ecological and biotechnological potential of Pseudovibrio bacteria which have been proposed to contribute to marine sponge health. SignificanceBacteria contribute to health and disease of plants and animals. Specialized metabolites produced by bacteria are important in mediating their behavior and the colonization of their hosts. We have identified a conserved gene cluster family in Pseudovibrio and Pseudomonas bacteria known to colonize marine animals and terrestrial plants, respectively. Using Pseudovibrio as a model, we show the encoded metabolites, which we termed pseudovibriamides, promote motility and decrease biofilms. In contrast to lipopeptides widely known to affect motility/biofilms, pseudovibriamides are not surfactants, but instead are linear peptides with a reversal in chain polarity. The discovery of pseudovibriamides expands current knowledge of bacteria collective behavior. The establishment of reverse genetics will enable exploration of the ecological and biotechnological potential of Pseudovibrio bacteria. ClassificationBiological Sciences, Microbiology