Research on Quorum Sensing of Pathogen Interfered by Intestinal Symbiotic Bacteria

Quorum sensing (QS) system controls important functions in bacteria, such as colonization, expansion, invading and pathogenicity. The infections caused by drug-resistant pathogens can be suppressed and eliminated by fecal microbiota transplantation and probiotics therapy. However, its molecular mechanism remains elusive. We hypothesized that intestinal symbiotic microbiota can disturb QS system of pathogens to suppress pathogens adhesion, infection and pathogenicity. In our research, bacteria were separated from patients who were diagnosed with digestive diseases and new-born infants with multiple culture conditions. The relationships between biofilm formation, pathogenicity and auto-inducer (AI) -1 QS system were analyzed, as well as the ability of intestinal symbiotic bacteria degrading the signaling molecules of acyl-homoserine lactones (AHLs). Then the pathogenicity of pathogens was analyzed when co-cultured with symbiotic bacteria. Various bacteria species were separated from infants and patients, including symbiotic bacteria and pathogens. Pseudomonas aeruginosa contains AI-1 QS system, in which AHLs are closely related to the biofilm formation and toxin expression in vitro. Some strains of intestinal symbiotic bacteria, such as Bacillus pumilus, Streptococcus gallolyticus subsp. Gallolyticus and Streptococcus pasteurianus, could degrade AHLs efficiently in vitro. When co-cultured with B. pumilus, the production of pyocyanin produced by P. aeruginosa was significantly affected, as well as the structure of biofilm. It suggested that symbiotic bacteria possibly degrade QS signal molecules to affect communication in vivo, as a result inhibiting pathogens infection. This study put forward and validated a new mechanism about transplanting fecal microbiota to treat antibiotic-resistant bacteria infections.