Effects of Elevated Carbon Dioxide on Environmental Microbes and Its Mechanisms: A Review

Before the industrial revolution, the atmospheric CO concentration was 180-330 ppm; however, fossil-fuel combustion and forest destruction have led to increased atmospheric CO concentration. CO capture and storage is regarded as a promising strategy to prevent global warming and ocean acidification and to alleviate elevated atmospheric CO concentration, but the leakage of CO from storage system can lead to rapid acidification of the surrounding circumstance, which might cause negative influence on environmental microbes. The effects of elevated CO on microbes have been reported extensively, but the review regarding CO affecting different environmental microorganisms has never been done previously. Also, the mechanisms of CO affecting environmental microorganisms are usually contributed to the change of pH values, while the direct influences of CO on microorganisms were often neglected. This paper aimed to provide a systematic review of elevated CO affecting environmental microbes and its mechanisms. Firstly, the influences of elevated CO and potential leakage of CO from storage sites on community structures and diversity of different surrounding environmental microbes were assessed and compared. Secondly, the adverse impacts of CO on microbial growth, cell morphology and membranes, bacterial spores, and microbial metabolism were introduced. Then, based on biochemical principles and knowledge of microbiology and molecular biology, the fundamental mechanisms 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 CO that need to be answered in the future were addressed.