Population dynamics and transcriptomic responses of Pseudomonas aeruginosa in a complex laboratory microbial community

Pseudomonas aeruginosa tends to be among the dominant species in multi-species bacterial consortia in diverse environments. To understand P. aeruginosa’s physiology and interactions with co-existing bacterial species in different conditions, we established physiologically reproducible 18 species communities, and found that P. aeruginosa dominated in mixed-species biofilm communities but not in planktonic communities. P. aeruginosa’s H1 type VI secretion system was highly induced in mixed-species biofilm consortia, compared with its monospecies biofilm, which was further demonstrated to play a key role in P. aeruginosa 's enhanced fitness over other bacterial species. In addition, the type IV pili and Psl exopolysaccharide were required for P. aeruginosa to compete with other bacterial species in the biofilm community. Our study showed that the physiology of P. aeruginosa is strongly affected by interspecies interactions, and both biofilm determinants and type VI secretion system contribute to higher P. aeruginosa 's fitness over other species in complex biofilm communities. Microbial ecology: transcriptome determinants for biofilm dominance Pseudomonas aeruginosa bacteria are highly adaptable and dominate different environments—notably biofilms—yet the biological and ecological factors that support this dominance are still poorly understood. Here, Yingying Cheng and Liang Yang at the Nanyang Technological University, Singapore, used multiplexed gene expression analysis of mixed-species microbial communities to monitor transcriptional changes in P. aeruginosa , and reveal the upregulation of the H1 type VI secretion system and the expression of the type IV pili and Psl exopolysaccharide as central events in establishing the dominance of P. aeruginosa over other bacterial species growing in biofilms. This work provides new insights into the factors that enhance the fitness of P. aeruginosa in multi-species communities, and exemplifies how transcriptome analyses can uncover the physiological properties that enable P. aeruginosa to overcome other microbial species and thrive in complex biofilms.