Effects of elevated carbon dioxide on environmental microbes and its mechanisms: A review

Before the industrial revolution, the atmospheric CO2 concentration was 180-330 ppm; however, fossil-fuel combustion and forest destruction have led to increased atmospheric CO2 concentration. CO2 capture and storage is regarded as a promising strategy to prevent globalwarming and ocean acidification and to alleviate elevated atmospheric CO2 concentration, but the leakage of CO2 from storage system can lead to rapid acidification of the surrounding circumstance, whichmight cause negative influence on environmentalmicrobes. The effects of elevated CO2 on microbes have been reported extensively, but the review regarding CO2 affecting different environmental microorganisms has never been done previously. Also, the mechanisms of CO2 affecting environmental microorganisms are usually contributed to the change of pH values, while the direct influences of CO2 on microorganisms were often neglected. This paper aimed to provide a systematic review of elevated CO2 affecting environmental microbes and its mechanisms. Firstly, the influences of elevated CO2 and potential leakage of CO2 from storage sites on community structures and diversity of different surrounding environmentalmicrobeswere assessed and compared. Secondly, the adverse impacts of CO2 on microbial growth, cellmorphology andmembranes, bacterial spores, andmicrobial metabolismwere introduced. Then, based on biochemical principles and knowledge ofmicrobiology and molecular biology, the fundamentalmechanisms of the influences of carbon dioxide on environmental microbes were discussed from the aspects of enzyme activity, electron generation and transfer, and key gene and protein expressions. Finally, key questions relevant to the environmental effect of CO2 that need to be answered in the future were addressed. (c) 2018 Elsevier B.V. All rights reserved.