Fichtel Katja, Mathes Falko, Könneke Martin, Cypionka Heribert, Engelen Bert
Paleomicrobiology, Institute for Chemistry and Biology of the Marine Environment, University of Oldenburg Oldenburg, Germany.
Front Microbiol. 2012 Feb 20;3:65. doi: 10.3389/fmicb.2012.00065. eCollection 2012.
On a global scale, crustal fluids fuel a large part of the deep-subseafloor biosphere by providing electron acceptors for microbial respiration. In this study, we examined bacterial cultures from sediments of the Juan de Fuca Ridge, Northeast Pacific (IODP Site U1301). The sediments comprise three distinctive compartments: an upper sulfate-containing zone, formed by bottom-seawater diffusion, a sulfate-depleted zone, and a second (∼140 m thick) sulfate-containing zone influenced by fluid diffusion from the basaltic aquifer. In order to identify and characterize sulfate-reducing bacteria, enrichment cultures from different sediment layers were set up, analyzed by molecular screening, and used for isolating pure cultures. The initial enrichments harbored specific communities of heterotrophic microorganisms. Strains affiliated to Desulfosporosinus lacus, Desulfotomaculum sp., and Desulfovibrio aespoeensis were isolated only from the top layers (1.3-9.1 meters below seafloor, mbsf), while several strains of Desulfovibrio indonesiensis and a relative of Desulfotignum balticum were obtained from near-basement sediments (240-262 mbsf). Physiological tests on three selected strains affiliated to Dv. aespoeensis, Dv. indonesiensis, and Desulfotignum balticum indicated that all reduce sulfate with a limited number of short-chain n-alcohols or fatty acids and were able to ferment either ethanol, pyruvate, or betaine. All three isolates shared the capacity of growing chemolithotrophically with H(2) as sole electron donor. Strain P23, affiliating with Dv. indonesiensis, even grew autotrophically in the absence of any organic compounds. Thus, H(2) might be an essential electron donor in the deep-subseafloor where the availability of organic substrates is limited. The isolation of non-sporeforming sulfate reducers from fluid-influenced layers indicates that they have survived the long-term burial as active populations even after the separation from the seafloor hundreds of meters above.
在全球范围内，地壳流体通过为微生物呼吸提供电子受体，为大部分深海海底生物圈提供能量。在本研究中，我们检测了东北太平洋胡安德富卡海岭（综合大洋钻探计划U1301站点）沉积物中的细菌培养物。这些沉积物包括三个不同的区域：由底层海水扩散形成的上部含硫酸盐区域、硫酸盐耗尽区域以及受玄武岩含水层流体扩散影响的第二个（约140米厚）含硫酸盐区域。为了鉴定和表征硫酸盐还原菌，我们建立了来自不同沉积层的富集培养物，通过分子筛选进行分析，并用于分离纯培养物。最初的富集培养物中含有特定的异养微生物群落。仅从表层（海底以下1.3 - 9.1米）分离出了隶属于湖生脱硫孢菌、脱硫肠状菌属和埃斯波脱硫弧菌的菌株，而从近基底沉积物（海底以下240 - 262米）中获得了几株印尼脱硫弧菌和波罗的海脱硫线菌的亲缘菌株。对隶属于埃斯波脱硫弧菌、印尼脱硫弧菌和波罗的海脱硫线菌的三株选定菌株进行的生理测试表明，它们都能利用有限数量的短链正醇或脂肪酸还原硫酸盐，并且能够发酵乙醇、丙酮酸或甜菜碱。所有这三株分离菌都具有以氢气作为唯一电子供体进行化能自养生长的能力。隶属于印尼脱硫弧菌的菌株P23甚至在没有任何有机化合物的情况下也能自养生长。因此，在深海海底有机底物可用性有限的地方，氢气可能是一种重要的电子供体。从受流体影响的层中分离出非芽孢形成的硫酸盐还原菌表明，即使在与数百米以上的海底分离后，它们作为活跃种群在长期埋藏中存活了下来。
