LCR 6013降解亚硝酸盐的途径及其亚硝酸盐还原酶的初步定位

The Degradation Pathway of Nitrite by LCR 6013 and the Primary Localization of Its Nitrite Reductase

研究了在De Man,Rogosa and Sharpe medium(简称MRS培养基)体系中NaCl、Vc对Lactobacillus casei subsp.rhamnosus6013(简称LCR 6013)降解亚硝酸盐的影响。并利用电子捕获-气相色谱法和靛酚蓝染色法确定亚硝酸盐的降解途径。通过测定LCR6013细胞中不同组分的酶活研究了亚硝酸盐还原酶(Nitrite reductase,NiR)的定位。在MRS体系中,NaCl、Vc浓度分别为0.75%、0.02%时,LCR 6013对亚硝酸盐的降解量最高分别为9.29μg/mL和9.89μg/mL,与对照比,此降解效果显著(p 0.01)。当NaNO2初始量为10.00μg/mL时,降解产物中含有28.81 10-6的N2O气体,没有NH4+。当NaNO2初始量为50.00μg/mL,在16 h时LCR 6013能够将NaNO2完全降解,14 h时N2O体积百分比含量最高为96.61 10-6;细胞周质间隙中NiR酶活是细胞质中的2.5倍。总之,在MRS体系中,LCR 6013能有效降解亚硝酸盐是源于细胞内亚硝酸盐还原酶NiR的作用;最可能通过NO2-NO N2O N2的途径进行降解,而非铵化作用;降解产物中含有N2O气体。

The effects of Vc, NaCl on the nitrites degradation by Lactobacillus casei subsp. rhamnosus 6013 （LCR 6013） in the De Man, Rogosa and Sharpe medium （MRS） were investigated. The degradation pathway was confirmed by electron capture gas-chromatography and indophenol blue colorimetric method. The nitrite reductase （NiR） localization was examined by measuring the enzyme activity of different cellular components from LCR 6013 cells. In MRS, the degraded nitrites concentration reached the highest to 9.29 μg/mL and 9.89 μg/mL when NaCl and Vc concentrations were 0.75 % and 0.02 %, respectively. To compare with the control, the degradation effect of treatment was significant （p≤0.01）. When the initial concentration of nitrites was 10.00 μg/mL, the degradation products contained 28.81×10^-6 N2O. The strain LCR 6013 completely degraded the nitrites with initial concentration of 50.00 μg/mL after 16 h incubation And the volume fraction of N2O reached 96.61？10-6 after 14 h. The enzyme activity of nitrites from the periplasm extraction was 2.5 fold higher than that from the cytoplasm extraction. In summary, the effective degradation of nitrites is due to the reaction of the nitrite reductase in the LCR 6013 cell. The most likely pathway of degradation was as follows：NO2-→NO→N2O→N2, rather than ammonification. The degradation products contain N2O gas.