Carbon and nitrogen assimilation in deep subseafloor microbial cells
Carbon and nitrogen assimilation in deep subseafloor microbial cells
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DOI：
10.1073/pnas.1107763108
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发表时间：
2011-11-08
影响因子：
11.1
通讯作者：
Inagaki, Fumio
中科院分区：
文献类型：
--
作者：
Morono, Yuki;Terada, Takeshi;Inagaki, Fumio
在全球浅层到深海海底沉积物中已观察到数量可观的微生物细胞。越来越多的证据表明，深层和古老的沉积物中有生命的微生物，那里的营养物质和能量的通量极低。然而，它们的生理和能量需求在很大程度上仍然未知。利用稳定同位素示踪剂培养和纳米级二次离子质谱技术，研究了来自日本下田半岛西北太平洋下更新世（460000年）沉积物219 m深的单个微生物细胞的碳氮同化活动动态。沉淀物样品与（13）C和/或（15）n标记的葡萄糖、丙酮酸、乙酸、碳酸氢盐、甲烷、铵和氨基酸在体外孵育。葡萄糖、丙酮酸和氨基酸（约占总细胞的76%）对（13）C和/或（15）N的显著掺入和生长产生了反应，而醋酸盐和碳酸氢盐的掺入没有促进生长。在这些底物中，碳酸氢盐的最大底物同化率为67 × 10(-18) mol/cell / d。碳同化和生长对甲烷的反应都不明显。从铵中吸收的氮与细胞总氮的原子比一直超过碳的原子比，这表明海底微生物在体外恢复时优先需要氮同化。我们的研究结果表明，埋藏最深的海底沉积微生物保持着代谢活动的潜力，其生长通常受能量限制，而不受C和N化合物可用性的限制。
Remarkable numbers of microbial cells have been observed in global shallow to deep subseafloor sediments. Accumulating evidence indicates that deep and ancient sediments harbor living microbial life, where the flux of nutrients and energy are extremely low. However, their physiology and energy requirements remain largely unknown. We used stable isotope tracer incubation and nanometer-scale secondary ion MS to investigate the dynamics of carbon and nitrogen assimilation activities in individual microbial cells from 219-m-deep lower Pleistocene (460,000 y old) sediments from the northwestern Pacific off the Shimokita Peninsula of Japan. Sediment samples were incubated in vitro with (13)C- and/or (15)N-labeled glucose, pyruvate, acetate, bicarbonate, methane, ammonium, and amino acids. Significant incorporation of (13)C and/or (15)N and growth occurred in response to glucose, pyruvate, and amino acids (similar to 76% of total cells), whereas acetate and bicarbonate were incorporated without fostering growth. Among those substrates, a maximum substrate assimilation rate was observed at 67 x 10(-18) mol/cell per d with bicarbonate. Neither carbon assimilation nor growth was evident in response to methane. The atomic ratios between nitrogen incorporated from ammonium and the total cellular nitrogen consistently exceeded the ratios of carbon, suggesting that subseafloor microbes preferentially require nitrogen assimilation for the recovery in vitro. Our results showed that the most deeply buried subseafloor sedimentary microbes maintain potentials for metabolic activities and that growth is generally limited by energy but not by the availability of C and N compounds.