Proteomic analysis reveals the strategies of Bacillus thuringiensis YBT‐1520 for survival under long‐term heat stress

Abstract

Bacillus thuringiensis (Bt) has been widely used for 50 years as a safe biopesticide for controlling agricultural and sanitary insect pests because of its insecticidal crystal proteins. In this study a proteomic approach was used to investigate the responses and survival strategies of Bt YBT-1520 under a long-term heat stress condition (42°C). Heat stress mainly influenced the characteristics of YBT-1520 on four aspects: (i) the abilities to synthesise insecticidal crystal proteins and other potential pathogenic factors were almost lost, (ii) cell adhesion and motility were also lost, (iii) cell did not sporulate, (iv) cell kept accumulating poly(3-hydroxybutyrate) (PHB). Proteomic analyses to the physiological changes of the strain revealed three strategies of YBT-1520 for survival under long-term heat stress. The first strategy is to up-regulate enzymes (BDH1, GuaB and PepA) for long-term heat stress tolerance. The second one is to down-regulate metabolic enzymes to reduce metabolic burden. The third strategy is to increase the synthesis and accumulation of PHB. Under heat stress condition, the bacterium adjusted its metabolism by up-/down-regulation and continuous accumulation of PHB. These strategies would help cells to gain more tolerance to heat stress.