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首页> 外文期刊>Journal of bacteriology >Respiratory chain of the alkalophilic bacterium Bacillus firmus RAB and its non-alkalophilic mutant derivative.
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Respiratory chain of the alkalophilic bacterium Bacillus firmus RAB and its non-alkalophilic mutant derivative.

机译：嗜碱细菌牢固芽孢杆菌RAB及其非嗜碱突变体衍生物的呼吸链。

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The membrane-bound respiratory chain components of alkalophilic Bacillus firmus RAB were studied by difference spectroscopy and oxidation-reduction potentiometric titrations. Cytochromes with the following midpoint potentials were identified at pH 9.0: a-type cytochromes, +110 and +210 mV; b-type cytochromes, +20, -120, -280, and -400 mV; and cytochrome c, +60 mV. Only the higher-potential cytochrome a showed an upward shift in midpoint potential when titrated at pH 7.0. Parallel studies of a non-alkalophilic mutant derivative of B. firmus RAB, strain RABN, revealed the presence of only one species each of a-, b-, and c-type cytochromes which exhibited midpoint potentials of +110, -150, and +160 mV, respectively, at pH 7.0. Membranes of both strains were found to contain menaquinone. At pH 9.0, NADH caused the reduction of essentially all of the cytochromes that were seen in fully reduced preparations of wild-type B. firmus RAB membranes. By contrast, at pH 7.0, NADH failed to appreciably reduce the b-type cytochromes. These findings may relate to our recent proposal that an inadequacy in energy transduction (production of a proton motive force) by the alkalophilic respiratory chain at pH 7.0 is what precludes the growth of B. firmus RAB at a neutral pH.
机译：通过差光谱法和氧化还原电位滴定法研究了嗜碱芽孢杆菌RAB的膜结合呼吸链成分。在pH 9.0时鉴定出具有以下中点电位的细胞色素：a型细胞色素，+110和+210 mV; b型细胞色素，+ 20，-120，-280和-400 mV;和细胞色素c，+ 60 mV。在pH 7.0滴定时，只有较高电势的细胞色素a在中点电势上显示出上移。对B.firmus RAB的非亲核突变体衍生物RABN进行的并行研究显示，a，b和c型细胞色素仅存在一种，其中点电位为+ 110，-150和在pH 7.0时分别为+160 mV。发现两种菌株的膜都含有甲萘醌。在pH 9.0时，NADH导致基本上所有的细胞色素减少，这在野生型牢固的芽孢杆菌RAB膜的完全还原制剂中可见。相比之下，在pH 7.0时，NADH无法明显还原b型细胞色素。这些发现可能与我们最近的建议有关，即在pH 7.0时，嗜碱呼吸链在能量转换（质子动力产生）方面的不足，是导致中性pH下坚强芽孢杆菌RAB不能生长的原因。

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