混合电子供体促进非光合微生物菌群固碳效率的分子生态机制

Molecular ecological mechanism of mixed electron donors promoting carbon fixation efficiency of non-photosynthetic microbial community

前期研究已从全国各地的表层海水中分离驯化得到了能有效固碳的非光合固碳微生物菌群(Non-photosynthetic microbial community,NPMC),并发现在好氧条件下,混合电子供体(Mixture of Electron Donors,MEDs)(配比为0.46%NaNO2、0.50%Na2S2O3和1.25%Na2S)能显著提高其固碳效率。但其与最佳H2作为电子供体相比促进效果如何,其促进机制是什么,尚未见有报道。本文在比较了NPMC以MED和H2为电子供体的固碳效率基础上,从NPMC的固碳基因丰度和表达活性角度分析了MED促进NPMC固碳效率的分子生态学机制。结果表明:(1)MED系统的固碳效率可以达到H2系统的水平,并显著高于传统的NH4^+系统的固碳效率;(2)卡尔文循环关键基因cbbL和cbbM在MED系统中的较高基因丰度和同时较高的表达可能是MED促进NPMC固碳效率的一个重要原因;(3)由于MED系统含有不同价态的N和S,有利于多种微生物生长,丰富了微生物多样性,为形成不同菌种之间的相互作用促进cbbL和cbbM的同时高表达提供了条件。

The non-photosynthetic microbial communities(NPMC)were isolated and domesticated from the surface seawater from all over the country in previous studies,and it was found that under aerobic conditions,mixed electron donors(MED)(consisted of 0.46% NaNO2,0.50% Na2S2O3 and 1.25% Na2S)could significantly improve its carbon fixation efficiency.However,compared with the optimal H2 as an electron donor,the promoting effect and the promoting mechanism were not reported.In this paper,based on the comparison of the carbon fixation efficiency of NPMC with MED and H2 as electron donors,the molecular ecological mechanism of MED promoting carbon fixation efficiency of NPMC was analyzed from the perspective of carbon fixation gene abundance and expression activity of NPMC.The results showed that:(1)The carbon fixation efficiency of the MED system could reach the level of the H2 system and was significantly higher than that of the traditional NH4^+ system;(2)The higher gene abundance and higher expression of Calvin Cycle key genes cbbL and cbbM in MED system might be an important reason for MED to promote the carbon fixation efficiency of NPMC;(3)Since MED system contained different valence states of N and S,it was beneficial to the growth of various microorganisms and enriched microbial diversity.It provided conditions for the interactions between different species which contributed to the simultaneous high expression of cbbL and cbbM genes.