甲烷菌通常存在于硫化物环境中,有利于铁(Fe)等过渡金属作为金属硫化物的沉淀,包括麦肯纳维(FeS)和黄铁矿(FeS2)。这些金属硫化物历来被认为是生物不可用的。尽管如此,产甲烷菌通常以硫化物(HS-)作为硫源培养,一个条件,预计将有利于金属沉淀,从而限制金属的可用性。最近的研究表明,产甲烷菌可以从FeS和FeS2中获取Fe和硫(S)以维持生长。因此,与提供有HS-的培养基相比,提供有FeS2的培养基应导致过渡金属的更高的可用性。这里,我们研究了过渡金属在硫化物下的可用性(即,提供有HS-作为唯一S源的细胞)与非硫化物(提供有FeS2作为唯一S源的细胞)条件会影响MethanosarcinabarkeriFusaro的金属蛋白质组。为了实现这一点,我们采用了尺寸排阻色谱,电感耦合等离子体质谱和鸟枪蛋白质组学。观察到铁的组成和丰度发生了显着变化,钴,镍,锌,和钼蛋白。差异中涉及甲烷生成和电子传递链的多亚基蛋白质复合物的化学计量和丰度的变化。我们的数据表明,在FeS2上生长时,M.barkeri利用了最小的铁硫簇复合物和典型的半胱氨酸生物合成蛋白,但使用了典型的Suf途径与tRNA-Sep半胱氨酸途径一起进行铁硫簇和半胱氨酸的生物合成在硫化物生长条件下。催化生化反应的蛋白质通常需要对硫具有高亲和力的过渡金属,生活的另一个必要元素。因此,金属和硫的可用性是交织在一起的,可能会对生物体的生物化学产生重大影响。产甲烷菌通常处于缺氧状态,富含硫化物(euxinic)的环境,有利于过渡金属沉淀为金属硫化物,从而产生假定的金属限制。最近,几种产甲烷菌已被证明可以从黄铁矿中获得铁和硫,一种丰富的硫化铁矿物,传统上被认为是生物学不可用的。这里介绍的工作为金属蛋白的分布提供了新的见解,和金属的吸收下生长的甲烷或黄铁矿生长条件。这种产甲烷菌在不同金属和硫条件下的彻底表征增加了我们对金属可用性对产甲烷菌的影响的理解。大概还有其他厌氧菌,居住在低氧环境中。
Methanogens often inhabit sulfidic environments that favor the precipitation of transition metals such as iron (Fe) as metal sulfides, including mackinawite (FeS) and pyrite (FeS2). These metal sulfides have historically been considered biologically unavailable. Nonetheless, methanogens are commonly cultivated with sulfide (HS-) as a sulfur source, a condition that would be expected to favor metal precipitation and thus limit metal availability. Recent studies have shown that methanogens can access Fe and sulfur (S) from FeS and FeS2 to sustain growth. As such, medium supplied with FeS2 should lead to higher availability of transition metals when compared to medium supplied with HS-. Here, we examined how transition metal availability under sulfidic (i.e., cells provided with HS- as sole S source) versus non-sulfidic (cells provided with FeS2 as sole S source) conditions impact the metalloproteome of Methanosarcina barkeri Fusaro. To achieve this, we employed size exclusion chromatography coupled with inductively coupled plasma mass spectrometry and shotgun proteomics. Significant changes were observed in the composition and abundance of iron, cobalt, nickel, zinc, and molybdenum proteins. Among the differences were alterations in the stoichiometry and abundance of multisubunit protein complexes involved in methanogenesis and electron transport chains. Our data suggest that M. barkeri utilizes the minimal iron-sulfur cluster complex and canonical cysteine biosynthesis proteins when grown on FeS2 but uses the canonical Suf pathway in conjunction with the tRNA-Sep cysteine pathway for iron-sulfur cluster and cysteine biosynthesis under sulfidic growth conditions.IMPORTANCEProteins that catalyze biochemical reactions often require transition metals that can have a high affinity for sulfur, another required element for life. Thus, the availability of metals and sulfur are intertwined and can have large impacts on an organismismal biochemistry. Methanogens often occupy anoxic, sulfide-rich (euxinic) environments that favor the precipitation of transition metals as metal sulfides, thereby creating presumed metal limitation. Recently, several methanogens have been shown to acquire iron and sulfur from pyrite, an abundant iron-sulfide mineral that was traditionally considered to be unavailable to biology. The work presented here provides new insights into the distribution of
metalloproteins, and metal uptake of Methanosarcina barkeri Fusaro grown under euxinic or pyritic growth conditions. Thorough characterizations of this methanogen under different metal and sulfur conditions increase our understanding of the influence of metal availability on methanogens, and presumably other anaerobes, that inhabit euxinic environments.