Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Tokyo 113-8656, Japan.
Biomolecular Characterization Unit, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
Sci Adv. 2018 Feb 16;4(2):eaao5682. doi: 10.1126/sciadv.aao5682. eCollection 2018 Feb.
Bacterial reduction of oxidized sulfur species (OSS) is critical for energy production in anaerobic marine subsurfaces. In organic-poor sediments, H has been considered as a major energy source for bacterial respiration. We identified outer-membrane cytochromes (OMCs) that are broadly conserved in sediment OSS-respiring bacteria and enable cells to directly use electrons from insoluble minerals via extracellular electron transport. Biochemical, transcriptomic, and microscopic analyses revealed that the identified OMCs were highly expressed on the surface of cells and nanofilaments in response to electron donor limitation. This electron uptake mechanism provides sufficient but minimum energy to drive the reduction of sulfate and other OSS. These results suggest a widespread mechanism for survival of OSS-respiring bacteria via electron uptake from solid minerals in energy-poor marine sediments.
细菌将氧化硫物种（OSS）还原对于厌氧海洋底层的能量生产至关重要。在有机质贫乏的沉积物中，H 被认为是细菌呼吸的主要能源。我们鉴定了在沉积物 OSS 呼吸细菌中广泛保守的外膜细胞色素（OMC），这些细胞色素使细胞能够通过细胞外电子传递直接利用来自不溶性矿物质的电子。生化、转录组和显微镜分析表明，鉴定出的 OMC 在外膜细胞和纳米丝上的表达量很高，以响应电子供体的限制。这种电子摄取机制提供了足够但最低的能量，以驱动硫酸盐和其他 OSS 的还原。这些结果表明，在能量贫乏的海洋沉积物中，OSS 呼吸细菌通过从固体矿物质中摄取电子来生存的机制是广泛存在的。
