Oxidative stress adaptation improves the heat tolerance of Pseudomonas fluorescens SN15-2

Pseudomonas fluorescens is a promising biocontrol agent that can inhibits a variety of plant pathogens, such as Rhizoctonia solani; Fusarium oxysporum; Botrytis cinerea, but because of its poor heat resistance, the survival rate is low during the formulation of the biocontrol agent. In this study, we explored the effects of oxidative stress adaptation on the heat tolerance of P. fluorescens SN15-2 and used tandem mass tag proteomic techniques to characterize proteome-level changes. The oxidative stress-adapted P. fluorescens SN15-2 had significantly lower mortality under subsequent high temperature conditions than the control group, indicating that oxidative stress adaptation can enhance their heat tolerance. The proteomic analysis was conducted after oxidative stress adaptation and 5903 proteins were identified. Among them, 150 proteins were differentially expressed. The proteomic results concurred with the verification analysis by parallel reaction monitoring assays. The functional analysis indicated that these differentially expressed proteins were involved in stress defence response, carbohydrate and energy metabolism, amino acid metabolism, signal transduction, membrane transport, nucleic acid metabolism, and lipid metabolism. Briefly, P. fluorescens SN15-2 enhances energy production and expression of a range of antioxidant substances and produces protein protectants, such as betaine and trehalose, after oxidative stress adaptation, thereby providing cross-protection for coping with subsequent high temperatures. Our findings contribute to understand the complexity of bacterial response to oxidative stress, and provide a basis for further study of oxidative stress response, tolerance mechanisms, and cross-protection mechanisms of P. fluorescens SN15-2 and other biocontrol bacteria.