Team:NCHU Taichung/Description

Project Inspiration

For reducing global warming, to increase clouds that could reflect sunlight and promote rainfall can be considered as one of the solutions. Our original idea is derived by the function of coccolithophores. Coccolithophores stand as the main group of marine phytoplankton and play crucial role in marine ecosystem as primary producer. Except organic carbon and calcium carbonate, they also produce dimethyl sulfide (DMS), which can be transformed into cloud condensation nuclei (CCN) and consequently affect climate. In our project, we attempt to increase their marine biomass through understanding their beneficial symbionts. And we also mimic their functions by adding carbon fixation pathways and DMS synthesis pathway into Escherichia coli, in order to produce CCN through anthropogenic carbon dioxide emissions.


To understand the beneficial symbionts of coccolithophores, antibiotics were used to treat marine phytoplankton culture and distinguish the effect by beneficial symbionts. One of the beneficial symbionts was isolated from non-antibiotic-treated culture and identified as cellulosimicrobium celluans. The possible symbiosis interactions between them and clues to enhance their biomass were discussed. On the other hand, the metabolic engineering approach to mimic the function of both carbon fixation and DMS production coccolithophores were conducted. Carbon fixation machinery such as phosphoenolpyruvate carboxylase (PEPC), ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) and phosphoribulokinase (PRK) were engaged for constructing the Carbon fixation pathway. Though coccolithophores often use DMSP (dimethylsulfoniopropionate) dependent pathway to produce DMS by the action of DMSP lyase, we decided to introduce a novel DMSP independent pathway into E. coli for generating DMS without limitation of marine environment. Our pathway depends on Methionine-gamma lyase (MegL) to release methanethiol (MeSH) from methionine, while methanethiol S-methyltransferase (mddA) catalyzes the methylation of methanethiol to DMS. The productivities of DMS were confirmed by Gas chromatography–mass spectrometry and the results suggest that the phosphoenolpyruvate carboxylase may play a crucial role in both carbon fixation and DMS production. Our results may offer actual biological strategies to reduce global warming.