Department of Microbiology, North Carolina State University, Raleigh, NC 27695, USA.
Biodegradation. 2010 Jul;21(4):525-41. doi: 10.1007/s10532-009-9321-8. Epub 2009 Dec 10.
In this study we have examined the effects of individual gasoline hydrocarbons (C(5-10,12,14) n-alkanes, C(5-8) isoalkanes, alicyclics [cyclopentane and methylcyclopentane] and BTEX compounds [benzene, toluene, ethylbenzene, m-, o-, and p-xylene]) on cometabolism of methyl tertiary butyl ether (MTBE) and tertiary butyl alcohol (TBA) by Mycobacterium austroafricanum JOB5. All of the alkanes tested supported growth and both MTBE and TBA oxidation. Growth on C(5-8) n-alkanes and isoalkanes was inhibited by acetylene whereas growth on longer chain n-alkanes was largely unaffected by this gas. However, oxidation of both MTBE and TBA by resting cells was consistently inhibited by acetylene, irrespective of the alkane used as growth-supporting substrate. A model involving two separate but co-expressed alkane-oxidizing enzyme systems is proposed to account for these observations. Cyclopentane, methylcyclopentane, benzene and ethylbenzene did not support growth but these compounds all inhibited MTBE and TBA oxidation by alkane-grown cells. In the case of benzene, the inhibition was shown to be due to competitive interactions with both MTBE and TBA. Several aromatic compounds (p-xylene > toluene > m-xylene) did support growth and cells previously grown on these substrates also oxidized MTBE and TBA. Low concentrations of toluene (<10 microM) stimulated MTBE and TBA oxidation by alkane-grown cells whereas higher concentrations were inhibitory. The effects of acetylene suggest strain JOB5 also has two distinct toluene-oxidizing activities. These results have been discussed in terms of their impact on our understanding of MTBE and TBA cometabolism and the enzymes involved in these processes in mycobacteria and other bacteria.
在这项研究中，我们研究了个体汽油烃（C(5-10,12,14)正构烷烃、C(5-8)异构烷烃、脂环烃[环戊烷和甲基环戊烷]和 BTEX 化合物[苯、甲苯、乙苯、间-、对-和邻-二甲苯]）对分枝杆菌 austroafricanum JOB5 共代谢甲基叔丁基醚（MTBE）和叔丁醇（TBA）的影响。所有测试的烷烃都支持生长和 MTBE 和 TBA 的氧化。乙炔抑制了 C(5-8)正构烷烃和异构烷烃的生长，但这种气体对长链正构烷烃的生长影响不大。然而，无论用作生长支持底物的烷烃如何，乙炔都能一致地抑制细胞休止期 MTBE 和 TBA 的氧化。提出了一个模型，涉及两个独立但共同表达的烷烃氧化酶系统，以解释这些观察结果。环戊烷、甲基环戊烷、苯和乙苯不能支持生长，但这些化合物都抑制了烷烃生长细胞的 MTBE 和 TBA 的氧化。在苯的情况下，抑制作用被证明是由于与 MTBE 和 TBA 的竞争相互作用。几种芳香族化合物（对二甲苯>甲苯>间二甲苯）确实支持生长，先前在这些底物上生长的细胞也氧化 MTBE 和 TBA。低浓度的甲苯（<10 μM）刺激了烷烃生长细胞的 MTBE 和 TBA 氧化，而较高浓度则具有抑制作用。乙炔的影响表明，菌株 JOB5 也具有两种不同的甲苯氧化活性。这些结果已经在它们对我们理解 MTBE 和 TBA 共代谢以及分枝杆菌和其他细菌中涉及这些过程的酶的影响方面进行了讨论。
