Abstract
Background: Microbial activities play a crucial role in the carbon and energy cycle of the ocean. Microbial communities in the MCP has been proposed the function of transforming carbon, yet the potential for direct CO 2 reduction to the organic carbon is rarely considered in the carbon cycle and energy transforming. Results: Here we showed a naturally inherent photo-driven bioprocess of CO 2 reduction producing C 1 -C 6 alkanes/alkenes by the marine microbial community with CO 2 consumption rate of 100.87 uM day -1 . Upon the metabolite profiles and metagenomic sequencing analysis, we revealed the mechanism of CO 2 conversion to hydrocarbons that CO 2 fixation was dominantly completed with the Calvin-Benson-Bassham cycle, tricarboxylic acid cycle, and Wood-Ljungdahl cycle, while nitrogenases, aldehyde decarbonylase and carboxylic acid reductase played the crucial roles on the hydrocarbon formations. As these insights, the pathway of CO 2 to hydrocarbons was proposed. Isolated microorganisms from the enriched community, including Pseudomonas sp. , Serratia sp. , Candidatus sp. , Clostridium sp. , Enterococcus sp ., Salmonella sp. , Rhodospirillum sp. , Thalassospira sp. , Thioclava sp. , Stenotrophomonas sp. and Desulfovibrio sp., were tentatively integrated for validating the hypothesized process. Results exhibited that the improved performance of CO 2 reduction to hydrocarbons was achieved by this group. Conclusions: This study demonstrated a natural microbial CO 2 reduction process contributing to the carbon and energy cycle in the ocean, and could provide a microbial “CO 2 -hydrogenation process” or “fischer-tropsch process” for industrial application.