Effects of Oxidative Challenge on Defensive Enzyme and Cofactors Level in Alkalibacterium sp.F26 / 微生物学通报

ABSTRACT

In this paper,a slight halophilic alkaliphile swain,Alkalibacterium sp.F26,which produced high level of intracellular CAT observed in previous research,was selected as a model microbial to explain the responses of this bacterium to oxidative stress.The results indicated that Alkalibacterium sp.F26 had obvious responses to higher concentration (＞1 mmol/L) of H2O2 than that to lower H2O2 (＜1 mmol/L) challenge from the aspects of defensive enzyme synthesis and cofactors level variation.As for catalase production,the activity increased up to 106.54 U/rag protein which was 1.76 fold of the control when cells were challenged by 3 mmol/L H2O2,but its activity only was 1.13 fold when H2P2 was 100 μmol/L.As far as energy state was concerned,ATP production and NAD+ generation were significantly inhibited from 20.55 μmol/L to 17.80 μmol/L and 69.89 μmol/L to 31.77 μmol/L,respectively,leading to the drop of energy charge from 0.77 to 0.68 and the increase of the portion of NADH/NAD+ from 0.08 to 0.41 in the former case.However,these effects were less distinct under lower concentration of H2O2.Except of the condition of 100 μmol/L H2O2,under which the activation of defensive mechanism resulted in an increase of ATE the level of ATP dropped from 22.69 μmol/L of the control to 22.38 μmol/L and 13.70 μmol/L when challenged by 50 μmol/L and 500 μmol/L H2O2.Besides,the concentration of NADH fluctuated and the NAD+ gradually reduced when H2O2 below 1 mmol/L.