Construction and characterization of recombinant systems for stress response analysis in pollutant-degrading rhodococci

Genus Rhodococcus is represented by Gram-positive, mycolate-containing non- sporulating actinobacteria that excel in their ability to withstand effects of various physical and chemical stressors. Their enormous metabolic capacity allows them to efficiently degrade a wide range of toxic compounds. To benefit from these capabilities, it is essential to know the molecular basis of their response to the stresses, the regulation of which is primarily controlled by σ factors of RNA polymerase. These σ factors are still poorly described in rhodococci. This thesis aims to explore the potential of Rhodococcus erythropolis CCM2595 as a model organism for studying stress responses in rhodococci. R. erythropolis ΔsigH mutant and single-plasmid strains have been constructed which allow studying promoter activities of genes responding to osmotic, heat, and oxidative stress by measurement of GFP fluorescence intensity, in the cells of R. erythropolis. Further, homologous two- plasmid strains, which support induced overproduction of s factors, were also constructed. Comparison with analogous Corynebacterium glutamicum host-based systems showed that the use of rhodococci themselves as hosts for plasmid systems is still very limited, probably due to the plasmid instability in rhodococcal cells. Thus, for routine..