Department of Microbiology and Public Health, Michigan State University, East Lansing, Michigan 48824-1101.
Appl Environ Microbiol. 1986 Oct;52(4):623-30. doi: 10.1128/aem.52.4.623-630.1986.
Gut microbiota from Reticulitermes flavipes termites catalyzed an H(2)-dependent total synthesis of acetate from CO(2). Rates of H(2)-CO(2) acetogenesis in vitro were 1.11 +/- 0.37 mumol of acetate g (fresh weight) h (equivalent to 4.44 +/- 1.47 nmol termite h) and could account for approximately 1/3 of all the acetate produced during the hindgut fermentation. Formate was also produced from H(2) + CO(2), as were small amounts of propionate, butyrate, and lactate-succinate. However, H(2)-CO(2) formicogenesis seemed largely unrelated to acetogenesis and was believed not to be a significant reaction in situ. Little or no CH(4) was formed from H(2) + CO(2) or from acetate. H(2)-CO(2) acetogenesis was inhibited by O(2), KCN, CHCl(3), and iodopropane and could be abolished by prefeeding R. flavipes with antibacterial drugs. By contrast, prefeeding R. flavipes with starch resulted in almost complete defaunation but had little effect on H(2)-CO(2) acetogenesis, suggesting that bacteria were the acetogenic agents in the gut. H(2)-CO(2) acetogenesis was also observed with gut microbiota from Prorhinotermes simplex, Zootermopsis angusticollis, Nasutitermes costalis, and N. nigriceps; from the wood-eating cockroach Cryptocercus punctulatus; and from the American cockroach Periplaneta americana. Pure cultures of H(2)-CO(2)-acetogenic bacteria were isolated from N. nigriceps, and a preliminary account of their morphological and physiological properties is presented. Results indicate that in termites, CO(2) reduction to acetate, rather than to CH(4), represents the main electron sink reaction of the hindgut fermentation and can provide the insects with a significant fraction (ca. 1/3) of their principal oxidizable energy source, acetate.
黄胸散白蚁肠道微生物可催化氢气依赖型 CO2 合成乙酸。体外氢气-二氧化碳产乙酸率为 1.11±0.37µmol乙酸/g（鲜重）h（相当于 4.44±1.47nmol 白蚁 h），约占后肠发酵过程中产生的所有乙酸的 1/3。氢气和二氧化碳也生成甲酸，还生成少量的丙酸、丁酸和乳酸-琥珀酸。然而，氢气-二氧化碳(formicogenesis)似乎与产乙酸作用关系不大，在原位可能不是一个重要反应。氢气和二氧化碳或乙酸几乎不生成甲烷。氧气、氰化钾、三氯甲烷和碘丙烷抑制氢气-二氧化碳产乙酸作用，用抗菌药物预先处理黄胸散白蚁可以完全抑制该反应。相反，用淀粉预先处理黄胸散白蚁导致几乎完全除虫，但对氢气-二氧化碳产乙酸作用影响很小，表明细菌是肠道中的产乙酸菌。从宽结胸白蚁、狭胸穿山甲、黑胸散白蚁和黑翅土白蚁的肠道微生物、食木蟑螂 Cryptocercus punctulatus 和美洲大蠊 Periplaneta americana 中也观察到氢气-二氧化碳产乙酸作用。从黑翅土白蚁中分离到纯培养的氢气-二氧化碳产乙酸细菌，并初步介绍了其形态和生理特性。结果表明，在后肠发酵过程中，白蚁将二氧化碳还原为乙酸而不是甲烷，这代表了主要的电子汇反应，可以为昆虫提供重要的氧化还原能量来源乙酸的一部分（约 1/3）。
