The Influence Of Environmental Factors On The Interaction Between Pseudomonas Aeruginosa And Other Microorganisms And Its Mechanism

Microorganisms are the most common cause of food spoilage.Food spoilage caused by microorganisms has brought huge economic losses to the food industry.In recent years,food spoilage caused by P.aeruginosa has attracted widespread attention.P.aeruginosa widely exists in soil,air,water and other environments,and often pollutes drinking water,meat products,dairy products,and fresh vegetables.Polymicrobial contamination are more prevalent and intractable in food industry compared with monomicrobial infection.Various environmental factors including nutritional conditions,pH,and salt concentration affect the growth of microorganisms.Thus,understanding the interaction between different microorganisms and the influence of common environmental factors on the interaction are important for the treatment of multi-microbial mixed pollution.In this study,the interaction between P.aeruginosa and common microorganisms in food and the influence of environmental factors on the interaction between P.aeruginosa and S.aureus were explored.Then,under low phosphate environment,the mechanism of the toxicity enhancement of P.aeruginosa was explored through RT-qPCR technology.1.The results of the co-cultivation of P.aeruginosa with S.aureus,E.coli,S.enteritidis,and L.monocytogenes show that(1)P.aeruginosa ATCC27853 and PAO1 killed S.aureus10071,and P.aeruginosa HQ only inhibited the growth of S.aureus 10071.(2)P.aeruginosa killed E.coli totally.(3)the growth of S.enteritidis and L.monocytogenes were inhibited by P.aeruginosa.2.Two different proliferative characteristics were found in P.aeruginosa: 67 P.aeruginosa killed S.aureus totally,and compared to the planktonic state,it took longer to kill S.aureus in the biofilm state.And for other 35 P.aeruginosa,they lived with S.aureus to 7 d in spite of the significant suppression on S.aureus.3.In a medium with a pH of 5-9,a glucose concentration of 0-10 g/L,a sodium chloride concentration of 0-40 g/L,and a phosphate concentration of 0-10 g/L,the growth of P.aeruginosa ATCC27853,PAO1,?lasIrhlI,HQ and S.aureus 10071 was not significantlyaffected.4.The pH,glucose concentration and sodium chloride concentration of the medium had no effects on the interaction between P.aeruginosa and S.aureus.Under the environment of low phosphate concentration,the virulence of HQ and ?lasIrhlI was enhanced and S.aureus10071 was killed.5.P.aeruginosa HQ and ?lasIrhlI were co-cultured with S.aureus 10071.In HQ,low phosphate activated Pho B-Pho R,which in turn activated IQS system,PQS system and Rhl I/Rhl R system.In ?lasIrhlI,low phosphate activated Pho B-Pho R,and then activated the IQS system and the PQS system.The activation of the QS system increased the virulence factors that were produced by P.aeruginosa HQ and ?lasIrhlI,and ultimately leading to the killing of S.aureus.6.S.aureus 10071 was co-cultured with P.aeruginosa HQ and ?lasIrhlI.The lack of phosphate resulted in a significant down-regulation of the lrgAB gene of S.aureus 10071,and the autolysis and death of S.aureus 10071.