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首页> 外文期刊>Archives of microbiology >Investigation of the fumarate metabolism of the syntrophic propionate-oxidizing bacterium strain MPOB
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Investigation of the fumarate metabolism of the syntrophic propionate-oxidizing bacterium strain MPOB

机译：腐殖酸丙酸氧化细菌菌株MPOB的富马酸酯代谢研究

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The growth of the syntrophic propionate-oxidizing bacterium strain MPOB in pure culture by fumarate disproportionation into carbon dioxide and succinate and by fumarate reduction with propionate, formate or hydrogen as electron donor was studied. The highest growth yield, 12.2 g dry cells/mol fumarate, was observed for growth by fumarate disproportionation. In the presence of hydrogen, formate or propionate, the growth yield was more than twice as low: 4.8, 4.6, and 5.2 g dry cells/mol fumarate, respectively. The location of enzymes that are involved in the electron transport chain during fumarate reduction in strain MPOB was analyzed. Fumarate reductase, succinate dehydrogenase, and ATPase were membrane-bound, while formate dehydrogenase and hydrogenase were loosely attached to the periplasmic side of the membrane. The cells contained cytochrome c, cytochrome b, menaquinone-6 and menaquinone-7 as possible electron carriers. Fumarate reduction with hydrogen in membranes of strain MPOB was inhibited by 2-(heptyl)4-hydroxyquinoline-N-oxide (HOQNO). This inhibition, together with the activity of fumarate reductase with reduced 2,3-dimethyl-1,4-naphtoquinone (DMNH2) and the observation that cytochrome b of strain MPOB was oxidized by fumarate, suggested that menequinone and cytochrome b are involved in the electron transport during fumarate reduction in strain MPOB. The growth yields of fumarate reduction with hydrogen or formate as electron donor were similar to the growth yield of Wolinella succinogenes. Therefore, it can be assumed that strain MPOB gains the same amount of ATP from fumarate reduction as W. succinogenes, i.e. 0.7 mel ATP/mol fumarate. This value supports the hypothesis that syntrophic propionate-oxidizing bacteria have to invest two-thirds of an ATP via reversed electron transport in the succinate oxidation step during the oxidation of propionate. The same electron transport chain that is involved in fumarate reduction may operate in the reversed direction to drive the energetically unfavourable oxidation of succinate during syntrophic propionate oxidation since (1) cytochrome b was reduced by succinate and (2) succinate oxidation was similarly inhibited by HOQNO as fumarate reduction. [References: 34]
机译：研究了通过富马酸酯歧化成二氧化碳和琥珀酸酯，以及通过用丙酸酯，甲酸或氢作为电子供体进行的富马酸酯还原，在纯培养物中合成营养的丙酸氧化细菌菌株MPOB的生长。通过富马酸酯歧化观察到最高的生长产量，即12.2g干细胞/ mol富马酸酯。在存在氢，甲酸盐或丙酸盐的情况下，生长产率低了两倍多：分别为4.8、4.6和5.2 g干细胞/摩尔富马酸盐。分析了MPOB菌株富马酸酯还原过程中电子传输链中涉及的酶的位置。富马酸酯还原酶，琥珀酸脱氢酶和ATPase被膜结合，而甲酸脱氢酶和氢化酶则松散地附着在膜的周质侧。细胞含有细胞色素c，细胞色素b，甲萘醌6和甲萘醌7作为可能的电子载体。 2-（庚基）4-羟基喹啉-N-氧化物（HOQNO）抑制了MPOB菌株膜中氢的富马酸酯还原。这种抑制作用以及还原的2,3-二甲基-1,4-萘醌（DMNH2）的富马酸酯还原酶的活性，以及​​观察到MPOB菌株的细胞色素b被富马酸酯氧化，表明甲萘醌和细胞色素b参与了该过程。菌株MPOB富马酸酯还原过程中的电子传输用氢或甲酸作为电子给体的富马酸酯还原的生长产率与沃林氏菌（Wolinella succinogenes）的生长产率相似。因此，可以假定MPOB菌株从富马酸酯的还原中获得了与琥珀酸W.琥珀酸基因相同量的ATP，即0.7 mel ATP / mol富马酸酯。该值支持以下假设：在丙酸的氧化过程中，在细菌的琥珀酸氧化步骤中，对营养的丙酸氧化细菌必须通过逆向电子传输来投入三分之二的ATP。在富营养的丙酸酯氧化过程中，与富马酸酯还原反应相同的电子传输链可能在相反的方向上驱动琥珀酸酯的能量上不利的氧化，因为（1）琥珀酸酯还原了细胞色素b，而（2）HOQNO抑制了琥珀酸酯的氧化作为减少富马酸。 [参考：34]

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