Xia Yongzhen, Lü Chuanjuan, Hou Ningke, Xin Yufeng, Liu Jihua, Liu Honglei, Xun Luying
State Key Laboratory of Microbial Technology, Shandong University, Jinan, China.
Institute of Oceanography, Shandong University, Jinan, China.
ISME J. 2017 Dec;11(12):2754-2766. doi: 10.1038/ismej.2017.125. Epub 2017 Aug 4.
Sulfide (HS, HS and S) oxidation to sulfite and thiosulfate by heterotrophic bacteria, using sulfide:quinone oxidoreductase (SQR) and persulfide dioxygenase (PDO), has recently been reported as a possible detoxification mechanism for sulfide at high levels. Bioinformatic analysis revealed that the sqr and pdo genes were common in sequenced bacterial genomes, implying the sulfide oxidation may have other physiological functions. SQRs have previously been classified into six types. Here we grouped PDOs into three types and showed that some heterotrophic bacteria produced and released HS from organic sulfur into the headspace during aerobic growth, and others, for example, Pseudomonas aeruginosa PAO1, with sqr and pdo did not release HS. When the sqr and pdo genes were deleted, the mutants also released HS. Both sulfide-oxidizing and non-oxidizing heterotrophic bacteria were readily isolated from various environmental samples. The sqr and pdo genes were also common in the published marine metagenomic and metatranscriptomic data, indicating that the genes are present and expressed. Thus, heterotrophic bacteria actively produce and consume sulfide when growing on organic compounds under aerobic conditions. Given their abundance on Earth, their contribution to the sulfur cycle should not be overlooked.
最近有报道称，异养细菌利用硫化物：醌氧化还原酶（SQR）和过硫化物双加氧酶（PDO）将硫化物（HS⁻、H₂S和S）氧化为亚硫酸盐和硫代硫酸盐，这可能是一种在高浓度下对硫化物进行解毒的机制。生物信息学分析表明，sqr和pdo基因在已测序的细菌基因组中很常见，这意味着硫化物氧化可能具有其他生理功能。SQR此前已被分为六种类型。在这里，我们将PDO分为三种类型，并表明一些异养细菌在有氧生长过程中会产生HS⁻并将有机硫中的HS⁻释放到顶空中，而其他细菌，例如铜绿假单胞菌PAO1，具有sqr和pdo基因则不会释放HS⁻。当sqr和pdo基因被删除时，突变体也会释放HS⁻。硫化物氧化型和非氧化型异养细菌都很容易从各种环境样本中分离出来。sqr和pdo基因在已发表的海洋宏基因组和宏转录组数据中也很常见，这表明这些基因是存在并表达的。因此，异养细菌在有氧条件下利用有机化合物生长时会积极地产生和消耗硫化物。鉴于它们在地球上的丰富程度，它们对硫循环的贡献不应被忽视。
