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Construction and characterization of recombinant systems for stress response analysis in pollutant-degrading rhodococci
Křenková, Lucie ; Štěpánek, Václav (advisor) ; Marešová, Helena (referee)
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...
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Stress responses in Rhodococcus strains
Křenková, Lucie ; Pátek, Miroslav (advisor) ; Cajthaml, Tomáš (referee)
Throughout the evolution, bacteria developed ingenious mechanisms which help them survive and grow in harsh conditions, where extreme temperatures, pH, changing water and osmotic activity occurs. Rhodococcus sp. cope with these conditions so efficiently they are able to grow in the presence of toxic compounds. Large genome of Rhodococcus sp. consists of a great amount of genes involved in a broad spectre of catabolic pathways. To use these skills in biotechnology, it is necessary to know stress response mechanisms well. In response to the changing environment Rhodococcus sp. use transcriptional regulators, two-component system and RNA polymerase sigma factors to tune the expression profiles of the genes. The upregulation of chaperons, chaperonins and proteases is the main pattern followed in most of the stress responses. Vast majority of stress responses is complex and groups of genes to react on them interfere too. Thus, it is very difficult to interpret the data of these studies. However, the great importance of understanding these mechanisms is unquestionable. Key words: stress response, bacteria, Rhodococcus, biotechnology, degradation, toxic compounds, sigma factor
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