The biodegradative capacity of bacteria in their natural habitats is affected by water availability. In this work, we have examined the activity and effector specificity of the transcriptional regulator XylR of the TOL plasmid pWW0 of Pseudomonas putida mt-2 for biodegradation of m-xylene when external water potential was manipulated with polyethylene glycol PEG8000. By using non-disruptive luxCDEAB reporter technology, we noticed that the promoter activated by XylR (Pu) restricted its activity and the regulator became more effector-specific towards head TOL substrates when cells were grown under water subsaturation. Such a tight specificity brought about by water limitation was relaxed when intracellular osmotic stress was counteracted by the external addition of the compatible solute glycine betaine. With these facts in hand, XylR variants isolated earlier as effector-specificity responders to the non-substrate 1,2,4-trichlorobenzene under high matric stress were re-examined and found to be unaffected by water potential in vivo. All these phenomena could be ultimately explained as the result of water potential-dependent conformational changes in the A domain of XylR and its effector-binding pocket, as suggested by AlphaFold prediction of protein structures. The consequences of this scenario for the evolution of specificities in regulators and the emergence of catabolic pathways are discussed.

• MeSH
• bakteriální proteiny genetika   metabolismus   MeSH
• DNA vazebné proteiny metabolismus   MeSH
• plazmidy MeSH
• promotorové oblasti (genetika) MeSH
• Pseudomonas putida * genetika   metabolismus   MeSH
• regulace genové exprese u bakterií MeSH
• transkripční faktory * genetika   metabolismus   MeSH
• xyleny metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• bakteriální proteiny MeSH
• DNA vazebné proteiny MeSH
• transkripční faktory * MeSH
• xyleny MeSH

Three types of contaminated soil from three geographically different areas were subjected to a constant supply of benzene or benzene/toluene/ethylbenzene/xylenes (BTEX) for a period of 3 months. Different from the soil from Brazil (BRA) and Switzerland (SUI), the Czech Republic (CZE) soil which was previously subjected to intensive in situ bioremediation displayed only negligible changes in community structure. BRA and SUI soil samples showed a clear succession of phylotypes. A rapid response to benzene stress was observed, whereas the response to BTEX pollution was significantly slower. After extended incubation, actinobacterial phylotypes increased in relative abundance, indicating their superior fitness to pollution stress. Commonalities but also differences in the phylotypes were observed. Catabolic gene surveys confirmed the enrichment of actinobacteria by identifying the increase of actinobacterial genes involved in the degradation of pollutants. Proteobacterial phylotypes increased in relative abundance in SUI microcosms after short-term stress with benzene, and catabolic gene surveys indicated enriched metabolic routes. Interestingly, CZE soil, despite staying constant in community structure, showed a change in the catabolic gene structure. This indicates that a highly adapted community, which had to adjust its gene pool to meet novel challenges, has been enriched.

• MeSH
• Bacteria klasifikace   genetika   izolace a purifikace   metabolismus   MeSH
• bakteriální proteiny genetika   metabolismus   MeSH
• benzen metabolismus   MeSH
• benzenové deriváty metabolismus   MeSH
• biodegradace MeSH
• biodiverzita MeSH
• látky znečišťující půdu metabolismus   MeSH
• půda chemie   MeSH
• půdní mikrobiologie * MeSH
• toluen metabolismus   MeSH
• xyleny metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH
• Geografické názvy
• Brazílie MeSH
• Česká republika MeSH
• Švýcarsko MeSH
• Názvy látek
• bakteriální proteiny MeSH
• benzen MeSH
• benzenové deriváty MeSH
• ethylbenzene MeSH Prohlížeč
• látky znečišťující půdu MeSH
• půda MeSH
• toluen MeSH
• xyleny MeSH