Escherichia coli O157:H7 is challenged by the presence of Pseudomonas, but successfully co-existed in dual-species microbial communities

Abstract

Escherichia coli O157:H7 and Pseudomonas were considered as common colonizers of fresh and spoilage meat, where they tended to live in the proximity. In this study, we tested the interplay between different isolates of E. coli O157:H7 and Pseudomonas in random two-by-two combinations grown as dual-species consortia. Results showed that the growth fitness of E. coli was not facilitated by the presence of all tested Pseudomonas strains, and vice versa. Representative combinations were further selected to investigate the property changes following the time course of biofilms formation as compared to single species. Cell counting confirmed that the growth of E. coli O157:H7 was challenged by the presence of Pseudomonas strains as previously described. Our findings shed new light on the evidence that the pathogenicity of E. coli O157:H7 was negatively affected by the presence of Pseudomonas according to the evaluation of spatial organization and genetic expression of virulence factors, which might be a naturally existing biological phenomenon constraining the safety risk of former strains in meat processing and preservation. Intriguingly, we observed that E. coli managed to stably co-exist at low cellular abundance in the progress of dual-species consortia, indicating successful adaptive mechanisms that need further investigations to uncover.

Keywords: Dual-species biofilms; Escherichia coli O157:H7; Interplay; Meat-borne Pseudomonas; Virulence gene expression.