Interspecies hydrogen transfer in anoxic ecosystems is essential for the complete microbial breakdown of organic matter to methane. Acetogenic bacteria are key players in anaerobic food webs and have been considered as prime candidates for hydrogen cycling. We have tested this hypothesis by mutational analysis of the hydrogenase in the model acetogen Acetobacterium woodii. Hydrogenase-deletion mutants no longer grew on H2 + CO2 or organic substrates such as fructose, lactate, or ethanol. Heterotrophic growth could be restored by addition of molecular hydrogen to the culture, indicating that hydrogen is an intermediate in heterotrophic growth. Indeed, hydrogen production from fructose was detected in a stirred-tank reactor. The mutant grew well on organic substrates plus caffeate, an alternative electron acceptor that does not require molecular hydrogen but NADH as reductant. These data are consistent with the notion that molecular hydrogen is produced from organic substrates and then used as reductant for CO2 reduction. Surprisingly, hydrogen cycling in A. woodii is different from the known modes of interspecies or intraspecies hydrogen cycling. Our data are consistent with a novel type of hydrogen cycling that connects an oxidative and reductive metabolic module in one bacterial cell, "intracellular syntrophy."

中文翻译：

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探戈并不总是需要两个：通过一个细菌细胞中的氢循环进行的“ Syntrophy”。

缺氧生态系统中的种间氢转移对于微生物将有机物完全分解为甲烷至关重要。产乙酸细菌是厌氧食物网中的关键角色，被认为是氢循环的主要候选者。我们已经通过对模型丙酮原木醋杆菌中的氢化酶进行突变分析来检验了这一假设。氢化酶缺失突变体不再在H2 + CO2或果糖，乳酸盐或乙醇等有机底物上生长。可以通过向培养物中添加分子氢来恢复异养生长，这表明氢是异养生长的中间产物。实际上，在搅拌釜反应器中检测到由果糖产生的氢气。该突变体在有机底物和咖啡因上生长良好，一种不需要分子氢但需要NADH作为还原剂的电子受体。这些数据与分子氢从有机底物产生然后用作还原CO2的还原剂的观点是一致的。令人惊讶的是，木柴中的氢循环不同于种间或种内氢循环的已知模式。我们的数据与一种新型的氢循环相一致，这种氢循环将一个细菌细胞中的氧化和还原代谢模块连接在一起，称为“细胞内营养”。