Super-robust synthetic microorganism can get chlorine resistance in advance and transfer their inserted DNA sequence in genome to indigenous bacteria in water

CRISPR-Cas gene editing tools have brought us to an era of synthetic biology that will change the world. Synthetic microorganisms (SMs) have brought enormous economic benefits and will contribute more in the future. Among them, super-robust SMs can overcome the stresses in bioproduction and further increase yield. However, when they are released into the environments, little is known about their fates and risks to human health. In this study, it was found that the gene editing super-robust SM could transfer its inserted DNA sequence in genome to the indigenous bacteria in surface water and showed stronger resistance to chlorine compared with wild-type bacteria. Chlorine disinfection did slight damage on cell membrane of super-robust SM, which decreased ATP leakage and DNA damage, and thereby promoted bacterial survival. Chlorine-injured super-robust SM retained high respiratory activity, and could resuscitate and regenerate. Less damage on super-robust SM cell membrane could prevent chlorine from entering the cells and resulted in lower ROS generation. Its DNA repair system and antioxidant system could still function under high concentrations of chlorine exposure. These findings provided new insights into the fates and environmental risks of SMs as an emerging biological pollutant in water supply system.