Transcriptomic analysis of rhodococcus sp. RHA1 responses to heat shock and osmotic stress

Rhodococcus sp. RMA1 is a soil actinomycete that is capable of degrading many aromatic compounds. Thus, it has potential applications in the pharmaceutical, the environmental, and the energy sectors. To efficiently exploit RHA1 in various applications, it is important to understand its responses to stress conditions commonly occurring in soil. This study focused on the global responses of exponentially growing RHA1 to heat shock and osmotic stress, primarily at the transcriptional level. Several genes that belong to the typical heat shock responses (encoding heat shock proteins), as well as the oxidative stress responses (encoding glutathione peroxidase, methionine sulfoxide reductase), were induced following heat shock. Several up-regulated genes following heat shock were related to fatty acid biosynthesis and metabolism. RHA1 adapts to osmotic stress by synthesizing the L-ectoine as a compatible solute, and possibly by turning on components of potassium transporters, KdpAB. It also induces genes encoding a tyrosine kinase and the DNA protection during starvation protein following osmotic stress. The translational machinery was repressed following both stresses; however, the repression was prolonged following the heat shock, which was lethal. Only 20 genes were found common to heat shock and osmotic stress responses. Among these are genes encoding a σ-factor similar to σF in M. tuberculosis and a transcriptional regulator similar to HspR in S. coelicolor. The induction of these two genes suggests central roles for them in stress responses, perhaps controlling other regulators that will promote or inhibit the expression of other genes, depending on the type of stress. Overall, this study provides improved understanding of adaptation mechanisms of rhodococci.Science, Faculty ofMicrobiology and Immunology, Department ofGraduat