Interspecies Effects Between Staphylococcus Aureus And Pseudomonas Aeruginosa During Co-cultivations

Polymicrobial contamination are more prevalent,hazardous and intractable in food industry than monomicrobial infection.Staphylococcus aureus and Pseudomonas aeruginosa are two of the most common biofilm-forming foodborne pathogens.It was reported that S.aureus and P.aeruginosa remain the relevant bacterial pathogens for waters system,meat and dairy.While the importance of these communities in food industry has long been understood,the advent of cutting-edge technologies is yielding new insights into the complexities and impacts of multi-species infections on contamination.In this study,prevalent S.aureus and P.aeruginosa were co-cultivated in planktonic and biofilm state to reveal different proliferative characteristics.Next,we did RNA-seq on the typical S.aureus and P.aeruginosa under coculturing and mono-culturing,building the interaction mechanisms between S.aureus and P.aeruginosa.1.Prevalent S.aureus and P.aeruginosa with different biofilm-forming capacity were cocultivated and two different proliferative characteristics were found: some P.aeruginosa killed S.aureus in 2 d to 4 d totally,but some P.aeruginosa lived with S.aureus to 7 d in spite of the significant suppression on S.aureus.The presence of S.aureus had no effect on P.aeruginosa.Strains with different group proliferative characteristics were on account of strains properties instead of biofilm-forming capacity.2.The suppression timepoint of S.aureus in nutrient-rich environment delayed more than 10 h.The 12-h-old metabolin and secretion of all P.aeruginosa had no effect on S.aureus;the 24-h-old metabolin and secretion of HQ had no effect on S.aureus;S.aureus first proliferated then were all killed with the supply of the 24-h-old metabolin and secretion of ATCC27853;the 24-h-old metabolin and secretion of co-cultivation of ATCC27853 and S.aureus suppressed the activity of S.aureus instead of killing.The surface roughness of S.aureus was increasing when co-cultivated with P.aeruginosa ATCC27853 in 12 h.However,no significant difference was found in the surface roughness of P.aeruginosa.3.P.aeruginosa secreted abundant extracellular polymeric substances(EPS)to build the scaffold of the mixed colony biofilm during the formation of multi-species biofilm.S.aureus was bedded in the EPS.The suppression against S.aureus in the mixed colony biofilm was gentler than that in planktonic in vitro.It took 5 d for P.aeruginosa to totally kill S.aureus in mixed biofilm.P.aeruginosa inhibited the activity of mature S.aureus biofilm.However,the structure of colony biofilm protected S.aureus from the killing of P.aeruginosa.4.RNA-seq revealed that alanine,aspartate and glutamate metabolism and TCA cycle was associated with the inhibiton from P.aeruginosa ATCC27853 against S.aureus.S.aureus accumulate alanine,aspartate and glutamate in the presence of P.aeruginosa ATCC27853 as a survival strategy,with the TCA cycle influenced.In the same time,Various S.aureus virulence factors were upregulated under co-cultivation,including staphylocoagulase,clumping factor and protease.5.S.aureus-killing strain P.aeruginosa ATCC27853 upregulated T6 SS gene clusters during co-cultivation with S.aureus,whereas P.aeruginosa HQ expressed on difference in secretion systems,suggesting that T6 SS was the important mechanism to suppress S.aureus.Two P.aeruginosa downregulated pyochelin pathway and the recptor FptA was suppressed.