Effect of temperature on Burkholderia pseudomallei growth, proteomic changes, motility and resistance to stress environments

Burkholderia pseudomallei is a flagellated, gram-negative environmental bacterium that causes melioidosis, a severe infectious disease of humans and animals in tropical areas. We hypothesised that B. pseudomallei may undergo phenotypic adaptation in response to an increase in growth temperature. We analysed the growth curves of B. pseudomallei strain 153 cultured in Luria-Bertani broth at five different temperatures (25 degrees C-42 degrees C) and compared the proteomes of bacteria cultured at 37 degrees C and 42 degrees C. B. pseudomallei exhibited the highest growth rate at 37 degrees C with modest reductions at 30 degrees C, 40 degrees C and 42 degrees C but a more marked delay at 25 degrees C. Proteome analysis revealed 34 differentially expressed protein spots between bacterial cultures at 42 degrees C versus 37 degrees C. These were identified as chaperones (7 spots), metabolic enzymes (12 spots), antioxidants (10 spots), motility proteins (2 spots), structural proteins (2 spots) and hypothetical proteins (1 spot). Of the 22 down-regulated proteins at 42 degrees C, redundancy in motility and antioxidant proteins was observed. qRT-PCR confirmed decreased expression of fliC and katE. Experiments on three B. pseudomallei strains demonstrated that these had the highest motility, greatest resistance to H2O2 and greatest tolerance to salt stress at 37 degrees C. Our data suggest that temperature affects B. pseudomallei motility and resistance to stress.