Effect Of Adversity Stress On Heat Tolerance Of Pseudomonas Fluorescens SN15-2 And Analysis Of Differentially Expressed Proteins After Oxidative Stress Adaptation

Pseudomonas fluorescens are important phytosanitary bacteria and plant growth-promoting rhizobacteria.They are widely distributed and can adapt to a variety of environments.However,P.fluorescens is not resistant to high temperatures during production and processing,and it is extremely susceptible to inactivation.Therefore,research on methods for improving the heat resistance of P..fluorescens and the mechanism therein have great significance for the future commercial application of P.fluorescens.The methods for improving the biocontrol ability and stress resistance of biological control bacteria with short-term adverse environmental stress adaptation have been reported,but no studies have been conducted on P.fluorescens.P.fluorescens SN15-2 isolated and screened by our laboratory showed good biocontrol ability,and its metabolites had good inhibitory effects on various pathogenic bacteria such as Ralstonia solanacearum.In order to improve the stress resistance of P.fluorescens SN15-2,we stimulated P.fluorescens SN15-2 to a short period of time with acid stress,oxidative stress and salt stress.The effects of different treatments on P.fluorescens SN15-2 were observed and measured.The results showed that acid stress could not improve the heat tolerance of P.fluorescens SN15-2,but the heat tolerance of P.fluorescens SN15-2 could be improved in varying degrees after 45 min and 30 min of acid stress with 300 mM NaCl and 25 mM H2O2,respectively,and the effect of 25 mM H2O2 treatment for 30 min was the best.Then,we explored the effects of oxidative stress on the biocontrol ability of P.fluorescens SN15-2 by detecting the indicators related to the biocontrol ability of P.fluorescens SN15-2.The results showed that the ability of biofilm formation,the ability of ferric phage production,the production of major antibiotics and the antagonistic effect on plant pathogens of P.fluorescens SN15-2 were not affected after adaptation to oxidative stress.On the basis of the above work.We used the TMT technique to detennine the protein expression of P..fluorescens SN15-2 adapted to oxidative stress,trying to elucidate the molecular mechanism of oxidative stress adapting to improve the heat resistance of P.fluorescens SN 15-2 at the protein level.TMT analysis showed that the effects of H2O2 treatment on P.fluorescens SN15-2 were mainly as follows:a)Increase the expression of antioxidant enzymes such as catalase and SOD to reduce the damage caused by oxidative stress;b)affect cell cycle,flagellum assembly and bacterial chemotaxis,stimulate quorum sensing system;c)increase the production of betaine,trehalose and other protective agents to protect cells from oxidation and heat damage.This study explored the methods to improve the heat resistance of biocontrol bacterial P.fluorescens SN15-2.It was found for the first time that oxidative stress could improve the heat resistance of P.fluorescens without affecting its control function.The molecular mechanism of oxidative stress adapting to enhance the heat resistance of P.fluorescens SN15-2 was preliminarily revealed.It provides a theoretical basis for the cultivation,preparation processing and industrial application of P.fluorescens SN15-2.