Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, 48109, USA.
Environ Microbiol. 2014 Jan;16(1):304-17. doi: 10.1111/1462-2920.12165. Epub 2013 Jun 30.
Chemolithotrophy is a pervasive metabolic lifestyle for microorganisms in the dark ocean. The SAR324 group of Deltaproteobacteria is ubiquitous in the ocean and has been implicated in sulfur oxidation and carbon fixation, but also contains genomic signatures of C1 utilization and heterotrophy. Here, we reconstructed the metagenome and metatranscriptome of a population of SAR324 from a hydrothermal plume and surrounding waters in the deep Gulf of California to gain insight into the genetic capability and transcriptional dynamics of this enigmatic group. SAR324's metabolism is signified by genes that encode a novel particulate hydrocarbon monooxygenase (pHMO), degradation pathways for corresponding alcohols and short-chain fatty acids, dissimilatory sulfur oxidation, formate dehydrogenase (FDH) and a nitrite reductase (NirK). Transcripts of the pHMO, NirK, FDH and transporters for exogenous carbon and amino acid uptake were highly abundant in plume waters. Sulfur oxidation genes were also abundant in the plume metatranscriptome, indicating SAR324 may also utilize reduced sulfur species in hydrothermal fluids. These results suggest that aspects of SAR324's versatile metabolism (lithotrophy, heterotrophy and alkane oxidation) operate simultaneously, and may explain SAR324's ubiquity in the deep Gulf of California and in the global marine biosphere.
化能自养是黑暗海洋中微生物普遍存在的代谢方式。δ变形菌的 SAR324 组在海洋中无处不在，与硫氧化和碳固定有关，但也包含 C1 利用和异养的基因组特征。在这里，我们重建了来自加利福尼亚湾深海热液羽流及其周围水域的 SAR324 种群的宏基因组和宏转录组，以深入了解这个神秘群体的遗传能力和转录动态。SAR324 的代谢由编码新型颗粒状烃单加氧酶（pHMO）、相应醇和短链脂肪酸降解途径、异化硫氧化、甲酸盐脱氢酶（FDH）和亚硝酸盐还原酶（NirK）的基因标志。在羽流水中，pHMO、NirK、FDH 和外源性碳和氨基酸摄取的转运蛋白的转录本丰度很高。硫氧化基因在羽流宏转录组中也很丰富，表明 SAR324 也可能在热液流体中利用还原态硫。这些结果表明，SAR324 多样的代谢方式（自养、异养和烷烃氧化）同时作用，这可能解释了 SAR324 在加利福尼亚湾深海和全球海洋生物群中的普遍存在。
