Nakano M M, Zuber P
Department of Biochemistry and Molecular Biology, Louisiana State University Medical Center, Shreveport 71130-3932, USA.
Annu Rev Microbiol. 1998;52:165-90. doi: 10.1146/annurev.micro.52.1.165.
There was a long-held belief that the gram-positive soil bacterium Bacillus subtilis is a strict aerobe. But recent studies have shown that B. subtilis will grow anaerobically, either by using nitrate or nitrite as a terminal electron acceptor, or by fermentation. How B. subtilis alters its metabolic activity according to the availability of oxygen and alternative electron acceptors is but one focus of study. A two-component signal transduction system composed of a sensor kinase, ResE, and a response regulator, ResD, occupies an early stage in the regulatory pathway governing anaerobic respiration. One of the essential roles of ResD and ResE in anaerobic gene regulation is induction of fnr transcription upon oxygen limitation. FNR is a transcriptional activator for anaerobically induced genes, including those for respiratory nitrate reductase, narGHJI.B. subtilis has two distinct nitrate reductases, one for the assimilation of nitrate nitrogen and the other for nitrate respiration. In contrast, one nitrite reductase functions both in nitrite nitrogen assimilation and nitrite respiration. Unlike many anaerobes, which use pyruvate formate lyase, B. subtilis can carry out fermentation in the absence of external electron acceptors wherein pyruvate dehydrogenase is utilized to metabolize pyruvate.
长期以来，人们一直认为革兰氏阳性土壤细菌枯草芽孢杆菌是严格的需氧菌。但最近的研究表明，枯草芽孢杆菌可以通过将硝酸盐或亚硝酸盐用作末端电子受体，或者通过发酵进行厌氧生长。枯草芽孢杆菌如何根据氧气和替代电子受体的可用性改变其代谢活性只是研究的一个重点。由传感激酶ResE和响应调节因子ResD组成的双组分信号转导系统在控制厌氧呼吸的调节途径中处于早期阶段。ResD和ResE在厌氧基因调控中的重要作用之一是在氧气限制时诱导fnr转录。FNR是厌氧诱导基因的转录激活因子，包括呼吸硝酸盐还原酶narGHJI的基因。枯草芽孢杆菌有两种不同的硝酸盐还原酶，一种用于硝酸盐氮的同化，另一种用于硝酸盐呼吸。相比之下，一种亚硝酸还原酶在亚硝酸氮同化和亚硝酸呼吸中都起作用。与许多使用丙酮酸甲酸裂解酶的厌氧菌不同，枯草芽孢杆菌可以在没有外部电子受体的情况下进行发酵，其中利用丙酮酸脱氢酶代谢丙酮酸。
