镍(Ni)是甲烷生成所需的许多酶的活性位点金属因子的关键成分,包括[NiFe]氢化酶,一氧化碳脱氢酶,和甲基CoM还原酶,导致产甲烷菌对镍的需求很高。然而,产甲烷菌通常居住在有利于镍作为金属硫化物矿物的固存环境中,如镍黄铁矿[(Ni,Fe)S2],溶解度低,不被认为是生物可利用的。最近,然而,几种不同的产甲烷菌模型(巴氏甲烷,伏甲烷球菌,已证明甲烷球菌可以还原溶解黄铁矿(FeS2),并利用溶解产物来满足铁和硫的生物合成需求。这里,使用M.BarkeriFusaro,和实验室合成(Ni,Fe)S2,使用透析膜从细胞中物理分离,我们表明,痕量镍(<20nM)从矿物中无价溶解可以支持甲烷生成和有限的生长,大约比已知的支持产甲烷的最低浓度低五倍。此外,当与(Ni,Fe)S2,M.barkeri促进(Ni,Fe)S2和同化的溶解镍,铁,硫是这些元素的唯一来源。还原溶解的细胞(Ni,Fe)S2的生物积累镍比用可溶性镍和硫化物生长的镍多约四倍,但具有相似的代谢偶联效率。虽然古细菌产甲烷菌吸收镍的机制尚不清楚,细菌Nik摄取系统的同源物在产甲烷菌基因组中无处不在。总的来说,这些观察结果表明(Ni,Fe)S2在缺氧环境中具有生物可利用性,产甲烷菌可以将这种矿物质转化为镍-,铁-,和含硫的金属酶来支持产甲烷和生长。重要性镍是一种必不可少的金属,由于太古代晚期火山活动的主要类型的变化限制了其可用性,并且元古代早期的euxinic条件增加,有利于其沉淀为硫化镍矿物,因此其可用性在地球历史上发生了巨大变化。本文提供的观察结果表明产甲烷菌,巴氏甲烷,可以从可溶性和矿物质来源获得低浓度(<20nM)的镍。此外,巴克里杆菌被证明能积极减少镍黄铁矿;使用溶解产品来满足他们的铁,硫磺,和镍需求;和生物积累镍。这些数据有助于解释M.barkeri(以及可能的其他产甲烷菌和厌氧菌)如何在当代和过去的缺氧或缺氧环境中获得镍。
Nickel (Ni) is a key component of the active site metallocofactors of numerous enzymes required for methanogenesis, including [NiFe]-hydrogenase, carbon monoxide dehydrogenase, and methyl CoM reductase, leading to a high demand for Ni among methanogens. However, methanogens often inhabit euxinic environments that favor the sequestration of nickel as metal-sulfide minerals, such as nickelian pyrite [(Ni,Fe)S2], that have low solubilities and that are not considered bioavailable. Recently, however, several different model methanogens (Methanosarcina barkeri, Methanococcus voltae, Methanococcus maripaludis) were shown to reductively dissolve pyrite (FeS2) and to utilize dissolution products to meet iron and sulfur biosynthetic demands. Here, using M. barkeri Fusaro, and laboratory-synthesized (Ni,Fe)S2 that was physically isolated from cells using dialysis membranes, we show that trace nickel (<20 nM) abiotically solubilized from the mineral can support methanogenesis and limited growth, roughly fivefold less than the minimum concentration known to support methanogenesis. Furthermore, when provided direct contact with (Ni,Fe)S2, M. barkeri promoted the reductive dissolution of (Ni,Fe)S2 and assimilated solubilized nickel, iron, and sulfur as its sole source of these elements. Cells that reductively dissolved (Ni,Fe)S2 bioaccumulated approximately fourfold more nickel than those grown with soluble nickel and sulfide but had similar metabolic coupling efficiencies. While the mechanism for Ni uptake in archaeal methanogens is not known, homologs of the bacterial Nik uptake system were shown to be ubiquitous across methanogen genomes. Collectively, these observations indicate that (Ni,Fe)S2 is bioavailable in anoxic environments and that methanogens can convert this mineral into nickel-, iron-, and sulfur-containing metalloenzymes to support methanogenesis and growth. IMPORTANCE Nickel is an essential metal, and its availability has changed dramatically over Earth history due to shifts in the predominant type of volcanism in the late Archean that limited its availability and an increase in euxinic conditions in the early Proterozoic that favored its precipitation as nickel sulfide minerals. Observations presented herein indicate that the methanogen, Methanosarcina barkeri, can acquire nickel at low concentration (<20 nM) from soluble and mineral sources. Furthermore, M. barkeri was shown to actively reduce nickelian pyrite; use dissolution products to meet their iron, sulfur, and nickel demands; and bioaccumulate nickel. These data help to explain how M. barkeri (and possibly other methanogens and anaerobes) can acquire nickel in contemporary and past anoxic or euxinic environments.