日本海洋研究開發(fā)機構(gòu)日前宣布,，其研究小組在青森縣八戶市近海海底距今約46萬年前的地層中采集到大量活的“超節(jié)能”微生物。由于這些微生物消耗能量的速度極慢,，研究人員推測這些生物已在嚴酷的環(huán)境中生存了數(shù)百年甚至數(shù)千年以上,。
研究小組2006年利用“地球”號深海探測船對八戶市約80公里外近海水深約1200米的海底進行了鉆探。結(jié)果在海底以下約200米,、距今約46萬年前的地層中發(fā)現(xiàn)每立方厘米含有超過1000萬個單細胞微生物,，并對這些微生物進行了培養(yǎng)。
這些微生物多數(shù)都是未知的,，大小只有0.5至1微米,。研究人員向這些微生物提供養(yǎng)分后，利用高性能的質(zhì)量分析儀進行檢測,，發(fā)現(xiàn)約80％的養(yǎng)分被吸收,，從而確認這些微生物是活的。
研究小組發(fā)現(xiàn),，如果向這些微生物投放葡萄糖等高營養(yǎng)物質(zhì),，細胞還會分裂并增殖。不過,，這些微生物吸收養(yǎng)分的速度不到大腸桿菌的十萬分之一,，極為緩慢。研究人員根據(jù)它們吸收和消耗能量的速度估算認為,，這些微生物可能活了數(shù)百到數(shù)千年,。
海洋研究開發(fā)機構(gòu)首席研究員諸野祐樹指出，這一發(fā)現(xiàn)將有助于弄清微生物參與的甲烷水合物和天然氣等形成的原因,。
這一成果已刊登在最新一期的美國《國家科學(xué)院院刊》（PNAS）網(wǎng)絡(luò)版上,。（生物谷 Bioon.com）
doi:10.1073/pnas.1107763108
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PMID:
Carbon and nitrogen assimilation in deep subseafloor microbial cells
Morono, Yuki; Terada, Takeshi; Nishizawa, Manabu; Ito, Motoo; Hillion, Fran?ois; Takahata, Naoto; Sano, Yuji; Inagaki, Fumio
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 13C- and/or 15N-labeled glucose, pyruvate, acetate, bicarbonate, methane, ammonium, and amino acids. Significant incorporation of 13C and/or 15N and growth occurred in response to glucose, pyruvate, and amino acids (∼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 × 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.
