UNLABELLED

Chronic polymicrobial infections involving and are prevalent, difficult to eradicate, and associated with poor health outcomes. Therefore, understanding interactions between these pathogens is important to inform improved treatment development. We previously demonstrated that is attracted to using type IV pili (TFP)-mediated chemotaxis, but the impact of attraction on growth and physiology remained unknown. Using live single-cell confocal imaging to visualize microcolony structure, spatial organization, and survival of during coculture, we found that interspecies chemotaxis provides a competitive advantage by promoting invasion into and disruption of microcolonies. This behavior renders susceptible to antimicrobials. Conversely, in the absence of TFP motility, cells exhibit reduced invasion of colonies. Instead, builds a cellular barrier adjacent to and secretes diffusible, bacteriostatic antimicrobials like 2-heptyl-4-hydroxyquinoline--oxide (HQNO) into the colonies. Reduced invasion leads to the formation of denser and thicker colonies with increased HQNO-mediated lactic acid fermentation, a physiological change that could complicate treatment strategies. Finally, we show that motility modifications of spatial structure enhance competition against . Overall, these studies expand our understanding of how TFP-mediated interspecies chemotaxis facilitates polymicrobial interactions, highlighting the importance of spatial positioning in mixed-species communities.

IMPORTANCE

The polymicrobial nature of many chronic infections makes their eradication challenging. Particularly, coisolation of and from airways of people with cystic fibrosis and chronic wound infections is common and associated with severe clinical outcomes. The complex interplay between these pathogens is not fully understood, highlighting the need for continued research to improve management of chronic infections. Our study unveils that is attracted to , invades into neighboring colonies, and secretes anti-staphylococcal factors into the interior of the colony. Upon inhibition of motility and thus invasion, colony architecture changes dramatically, whereby is protected from antagonism and responds through physiological alterations that may further hamper treatment. These studies reinforce accumulating evidence that spatial structuring can dictate community resilience and reveal that motility and chemotaxis are critical drivers of interspecies competition.