State Key Laboratory of Microbial Technology, Microbial Technology Institute, Shandong Universitygrid.27255.37, Qingdao, People's Republic of China.
Department of Pathogen Biology, School of Basic Medical Sciences, Shandong First Medical University & Shandong Academy of Medical Sciencegrid.410587.fs, Jinan, People's Republic of China.
Microbiol Spectr. 2022 Aug 31;10(4):e0043622. doi: 10.1128/spectrum.00436-22. Epub 2022 Jun 28.
Thermotoga maritima is an anaerobic hyperthermophilic bacterium that efficiently produces H by fermenting carbohydrates. High concentration of H inhibits the growth of T. maritima, and S could eliminate the inhibition and stimulate the growth through its reduction. The mechanism of T. maritima sulfur reduction, however, has not been fully understood. Herein, based on its similarity with archaeal NAD(P)H-dependent sulfur reductases (NSR), the ORF THEMA_RS02810 was identified and expressed in Escherichia coli, and the recombinant protein was characterized. The purified flavoprotein possessed NAD(P)H-dependent S reductase activity (1.3 U/mg for NADH and 0.8 U/mg for NADPH), polysulfide reductase activity (0.32 U/mg for NADH and 0.35 U/mg for NADPH), and thiosulfate reductase activity (2.3 U/mg for NADH and 2.5 U/mg for NADPH), which increased 3~4-folds by coenzyme A stimulation. Quantitative RT-PCR analysis showed that was upregulated together with the , , and genes when the strain grew in S- or thiosulfate-containing medium. The mechanism for sulfur reduction in T. maritima was discussed, which may affect the redox balance and energy metabolism of T. maritima. Genome search revealed that NSR homolog is widely distributed in thermophilic bacteria and archaea, implying its important role in the sulfur cycle of geothermal environments. The reduction of S and thiosulfate is essential in the sulfur cycle of geothermal environments, in which thermophiles play an important role. Despite previous research on some sulfur reductases of thermophilic archaea, the mechanism of sulfur reduction in thermophilic bacteria is still not clearly understood. Herein, we confirmed the presence of a cytoplasmic NAD(P)H-dependent polysulfide reductase (NSR) from the hyperthermophile T. maritima, with S, polysulfide, and thiosulfate reduction activities, in contrast to other sulfur reductases. When grown in S- or thiosulfate-containing medium, its expression was upregulated. And the putative membrane-bound MBX and Rnf may also play a role in the metabolism, which might influence the redox balance and energy metabolism of T. maritima. This is distinct from the mechanism of sulfur reduction in mesophiles such as Wolinella succinogenes. NSR homologs are widely distributed among heterotrophic thermophiles, suggesting that they may be vital in the sulfur cycle in geothermal environments.
海洋栖热菌是一种厌氧嗜热菌，能够高效地通过发酵碳水化合物生产 H。高浓度的 H 会抑制海洋栖热菌的生长，而 S 可以通过还原作用消除抑制并刺激生长。然而，海洋栖热菌的硫还原机制尚未完全阐明。在此，基于其与古菌 NAD(P)H 依赖型硫还原酶（NSR）的相似性，鉴定并在大肠杆菌中表达了 ORF THEMA_RS02810，对重组蛋白进行了表征。纯化的黄素蛋白具有 NAD(P)H 依赖型 S 还原酶活性（NADH 为 1.3 U/mg，NADPH 为 0.8 U/mg）、多硫化物还原酶活性（NADH 为 0.32 U/mg，NADPH 为 0.35 U/mg）和硫代硫酸盐还原酶活性（NADH 为 2.3 U/mg，NADPH 为 2.5 U/mg），辅酶 A 的刺激可使这些活性提高 3~4 倍。定量 RT-PCR 分析表明，当菌株在 S 或硫代硫酸盐存在的培养基中生长时， 与 、 、 和 基因一起上调。讨论了海洋栖热菌的硫还原机制，这可能会影响海洋栖热菌的氧化还原平衡和能量代谢。基因组搜索显示，NSR 同源物广泛分布于嗜热细菌和古菌中，这表明其在温泉环境中的硫循环中具有重要作用。 S 和硫代硫酸盐的还原对于温泉环境中的硫循环至关重要，其中嗜热菌发挥着重要作用。尽管先前对一些嗜热古菌的硫还原酶进行了研究，但嗜热细菌的硫还原机制仍不清楚。在此，我们从海洋栖热菌中证实了一种细胞质 NAD(P)H 依赖型多硫化物还原酶（NSR）的存在，该酶具有 S、多硫化物和硫代硫酸盐还原活性，与其他硫还原酶不同。当在含有 S 或硫代硫酸盐的培养基中生长时，其表达上调。而假定的膜结合 MBX 和 Rnf 也可能在代谢中发挥作用，这可能会影响海洋栖热菌的氧化还原平衡和能量代谢。这与沃尔林氏梭菌等中温菌的硫还原机制不同。NSR 同源物广泛分布于异养嗜热菌中，表明它们可能在温泉环境中的硫循环中至关重要。
