Interspecies and Intraspecies Signals Synergistically Regulate Lysobacter enzymogenes Twitching Motility

Abstract

The twitching motility of bacteria is closely related to environmental adaptability and pathogenic behaviors. <i>Lysobacter</i> is a good genus in which to study twitching motility because of the complex social activities and distinct movement patterns of its members. Regardless, the mechanism that induces twitching motility is largely unknown. In this study, we found that the interspecies signal indole caused <i>Lysobacter</i> to have irregular, random twitching motility with significantly enhanced speed. Deletion of <i>qseC</i> or <i>qseB</i> from the two-component system for indole signaling perception resulted in the disappearance of rapid, random movements and significantly decreased twitching activity. Indole-induced, rapid, random twitching was achieved through upregulation of expression of gene cluster <i>pilE1-pilY₁1-pilX1-pilW1-pilV1-fimT1</i> In addition, under conditions of extremely low bacterial density, individual <i>Lysobacter</i> cells grew and divided in a stable manner <i>in situ</i> without any movement. The intraspecies quorum-sensing signaling factor 13-methyltetradecanoic acid, designated <i>L. enzymogenes</i> diffusible signaling factor (<i>Le</i>DSF), was essential for <i>Lysobacter</i> to produce twitching motility through indirect regulation of gene clusters <i>pilM-pilN-pilO-pilP-pilQ</i> and <i>pilS1-pilR-pilA-pilB-pilC</i> These results demonstrate that the motility of <i>Lysobacter</i> is induced and regulated by indole and <i>Le</i>DSF, which reveals a novel theory for future studies of the mechanisms of bacterial twitching activities.<b>IMPORTANCE</b> The mechanism underlying bacterial twitching motility is an important research area because it is closely related to social and pathogenic behaviors. The mechanism mediating cell-to-cell perception of twitching motility is largely unknown. Using <i>Lysobacter</i> as a model, we found in this study that the interspecies signal indole caused <i>Lysobacter</i> to exhibit irregular, random twitching motility via activation of gene cluster <i>pilE1-pilY₁1-pilX1-pilW1-pilV1-fimT1</i> In addition, population-dependent behavior induced by 13-methyltetradecanoic acid, a quorum-sensing signaling molecule designated <i>Le</i>DSF, was involved in twitching motility by indirectly regulating gene clusters <i>pilM-pilN-pilO-pilP-pilQ</i> and <i>pilS1-pilR-pilA-pilB-pilC</i> The results demonstrate that the twitching motility of <i>Lysobacter</i> is regulated by these two signaling molecules, offering novel clues for exploring the mechanisms of twitching motility and population-dependent behaviors of bacteria.