Effects Of Pyocyanin On The Growth And Biofilm Formation Of Foodborne Bacteria:A Preliminary Study

Foodborne bacteria are the main cause of foodborne diseases.In the food production and processing environment,Foodborne bacteria is able to become biofilm to inprove the food safety risks,which increased the stress resistance and stock the ceilings,flooring,product delivery pipes and production containers,especially some wet and difficult to clean the surface of the material of the factory.So we need to find new ways and new targets to effectively block the formation of biofilm,eliminating cross infection/contamination.Pyocyanin is a secondary metabolite with redox activity which is secreted by Pseudomonas aeruginosa.Research shows,pyocyanin could be used to interfere with a variety of cellular functions in host cells including electron transport,cellular respiration,energy transfer,gene expression and innate immune mechanisms.However,it have not been reported that pyocyanin were producted from foodborne Pseudomonas aeruginosa and have effect on the growth of common foodborne bacteria and the formation of biofilm in food processing environment.Based on the redox properties of pyocyanin,the production of pyocyanin and growth of Pseudomonas aeruginosa in different solutions influenced the formation of biofilm was studied by scanning electrochemical microscopy(SECM)and spectrophotometer.The main results are as follows:1.This article established a method that combining the square wave voltammetry(SWV)and spectrophotometer determine the growth of Pseudomonas aeruginosa and PYO.For SWV,PYO has a maximum current peak at-0.33 V,which could be used as a qualitative and quantitative measure of the characteristic peaks of PYO during the growth of Pseudomonas aeruginosa;for spectrophotometry,the maximum absorption wavelength of PYO is 685 nm,and it could be used to determine PYO qualitatively and quantitatively during the growth of Pseudomonas aeruginosa.The growth of bacteria and the content of PYO were studied by spectrophotometry under the condition of sufficient oxygen shaking culture(sufficient oxygen)and static culture(oxygen deficiency).The result shows that PYO played a role in mediating biofilm formation.2.The effects of different concentrations(0?mol/L,30??mol/L,50?mol/L,70?mol/L)on the growth of three common foodborne bacteria(Pseudomonas aeruginosa,Pseudomonas fluorescens and Escherichia coli)in food processing environment were studied by spectrophotometry.The result shows,different concentrations of PYO had a certain effect on the growth of Pseudomonas aeruginosa,and inhibited the growth of Pseudomonas fluorescens and Escherichia coli in varying degrees.The higher concentration of PYO,the stronger inhibitory effect.Among them,70?mol/L PYO had the strongest inhibitory effect on the growth of Escherichia coli.The effects that different antioxidant agents(NAC,SOD,AA)inhbitted the PYO during the growth of Escherichia coli were studied.Different antioxidants had different effects on bacterial cells,but fat-soluble molecule(NAC)was able to pass through the cell membrane,its protective effect on bacteria was better than(SOD)and(AA).3.The result shows that the inhibition of PYO on the growth of foodborne bacteria was mainly based on its oxidative activity that produced reactive oxygen free radicals,and its own was not able to remove oxygen free radicals.And the promotion of Pseudomonas aeruginosa would be related to its growth in the formation of biofilm.The concentration of PYO in the culture system(LB,NB and NaCl)at different days(3 and 6 days)was detected by SWV in real time.At the same time,the morphological observation was carried out by microscopic observation andcrystal violet dyeing.The result shows,PYO would exert positive effect on the biofilm formation of Pseudomonas aeruginosa,The higher concentration of pyocyanin,Pseudomonas aeruginosa is more likely to become the biofilm;nutrient-rich hypoxic environment was more likely to promote the formation of bioflim;withextremely harsh environmental conditions(NaCl system),Biofilm was the main form of the Pseudomonas aeruginosa.Thus we can see,PYO plays an important role in the formation and development of Pseudomonas aeruginosa.It is presumed that electron transport as an electron carrier is involved in the electron transport in the biofilm,which could provide energy for the bacteria and plays an important role in maintaining the metabolism of bacteria and BF.The result shows that SECM has a unique advantage in real-time,in situ,lossless and on-line analysis of biological system redox information,which would provide a technical support for blocking of the formation of bacteria biofilm for food industry.