Sulfur metabolites that facilitate oceanic phytoplankton-bacteria carbon flux
Sulfur metabolites that facilitate oceanic phytoplankton-bacteria carbon flux
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DOI：
10.1038/s41396-019-0455-3
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发表时间：
2019-10-01
期刊：
影响因子：
11
通讯作者：
Moran, Mary Ann
中科院分区：
文献类型：
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作者：
Landa, Marine;Burns, Andrew S.;Moran, Mary Ann
与生物可利用的氮和磷不同，氮和磷在表层海水中的浓度通常是有限的，硫以硫酸盐的形式丰富，不被认为会限制海洋微生物的活动。尽管如此，在一个海洋细菌从共培养的浮游植物中获得所有碳的模型系统中，细菌基因表达表明，至少有七种溶解的有机硫（DOS）代谢物支持细菌异养。这些不稳定的海洋鞭毛藻和硅藻的外代谢产物包括牛磺酸、n -乙酰牛磺酸、异硫酸盐、胆碱-硫酸酯、半胱氨酸、2,3-二羟基丙烷-1-磺酸盐（DHPS）和二甲基磺丙酸盐（DMSP）。利用该模型系统中鉴定的化合物，我们通过挖掘塔拉海洋诊断基因数据集来评估硫代谢物在海洋碳循环中的作用。在调查的140万个细菌基因组当量中，对具有DOS代谢物利用能力的基因组频率的估计范围很广，从每190个基因组中只有1个（对于C2磺酰异硫酸盐）到每5个基因组中有1个（对于磺化化合物DMSP）。能够参与DOS转化的细菌主要是海洋表层的Alphaproteobacteria，但在中深海深处的SAR324、酸化微生物和Gammaproteobacteria则占主导地位，在中深海，利用硫代谢物的能力比表层细菌高一半以上。一组丰富多样的具有DOS转化遗传能力的海洋细菌的发现，证明了硫代谢物在远洋海洋碳循环中的重要作用。
Unlike biologically available nitrogen and phosphorus, which are often at limiting concentrations in surface seawater, sulfur in the form of sulfate is plentiful and not considered to constrain marine microbial activity. Nonetheless, in a model system in which a marine bacterium obtains all of its carbon from co-cultured phytoplankton, bacterial gene expression suggests that at least seven dissolved organic sulfur (DOS) metabolites support bacterial heterotrophy. These labile exometabolites of marine dinoflagellates and diatoms include taurine, N-acetyltaurine, isethionate, choline-O-sulfate, cysteate, 2,3-dihydroxypropane-1-sulfonate (DHPS), and dimethylsulfoniopropionate (DMSP). Leveraging from the compounds identified in this model system, we assessed the role of sulfur metabolites in the ocean carbon cycle by mining the Tara Oceans dataset for diagnostic genes. In the 1.4 million bacterial genome equivalents surveyed, estimates of the frequency of genomes harboring the capability for DOS metabolite utilization ranged broadly, from only 1 out of every 190 genomes (for the C2 sulfonate isethionate) to 1 out of every 5 (for the sulfonium compound DMSP). Bacteria able to participate in DOS transformations are dominated by Alphaproteobacteria in the surface ocean, but by SAR324, Acidimicrobiia, and Gammaproteobacteria at mesopelagic depths, where the capability for utilization occurs in higher frequency than in surface bacteria for more than half the sulfur metabolites. The discovery of an abundant and diverse suite of marine bacteria with the genetic capacity for DOS transformation argues for an important role for sulfur metabolites in the pelagic ocean carbon cycle.