Bacteria of the radiation resistant genus ππ¦πͺπ―π°π€π°π€π€πΆπ΄ have a high resistance to the lethal and mutagenic effects of many DNA damaging agents, however, the mechanisms involved in the response of these bacteria to oxidative stress are poorly understood. To investigate antioxidant enzyme responses in ππ¦πͺπ―π°π€π°π€π€πΆπ΄ sp., the types of catalase and superoxide dismutase (SOD) produced by these bacteria were identified by visualization of the enzyme activities on non-denaturing polyacrylamide gels (PAGE) and the growth inhibition of selected strains by various concentrations of hydrogen peroxide and paraquat (a superoxide generating agent) was tested. ππ¦πͺπ―π°π€π°π€π€πΆπ΄ sp. were found to be more resistant to hydrogen peroxide and more sensitive to paraquat than ππ΄π€π©π¦π³πͺπ€π©πͺπ’ π€π°ππͺ K12. They possess relatively high levels of catalase and exhibit similar electrophoretic patterns on catalase zymograms compared to π. π€π°ππͺ, but all the tested strains produce only one SOD except ππ¦πͺπ―π°π€π°π€π€πΆπ΄ π³π’π₯πͺπ°π±π©πͺππΆπ΄ which produces two. The two catalases of ππ¦πͺπ―π°π€π°π€π€πΆπ΄ π³π’π₯πͺπ°π₯πΆπ³π’π―π΄ were found to be regulated independently. Cultures of π. π³π’π₯πͺπ°π₯πΆπ³π’π―π΄, when pretreated with sublethal levels of hydrogen peroxide, became relatively resistant to the lethal effects of HβOβ and exhibited higher levels of catalase than untreated control cultures. The pretreated cells were also relatively resistant to UV-and Ξ³-ray-mediated lethality. These results suggest that ππ¦πͺπ―π°π€π°π€π€πΆπ΄ sp. possess inducible defense mechanisms against the deleterious effects of oxidants and ionizing and UV radiation. The resistance to the lethal effects of hydrogen peroxide and UV radiation can not be induced by pretreatment with sublethal levels of hydrogen peroxide in π. π³π’π₯πͺπ°π₯πΆπ³π’π―π΄ rec30 mutant. Effects of manganese and magnesium on the growth and catalase activity of π. π³π’π₯πͺπ°π₯πΆπ³π’π―π΄ were determined. Homology between π. π€π°ππͺ catalase and SOD genes and those of ππ¦πͺπ―π°π€π°π€π€πΆπ΄ sp. was tested by Southern blot analysis using previously cloned genes from π. π€π°ππͺ. / Thesis / Master of Science (MS)
Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/22938 |
Date | 09 1900 |
Creators | Wang, Ping |
Contributors | Schellhorn, H. E., Biology |
Source Sets | McMaster University |
Language | English |
Detected Language | English |
Type | Thesis |
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