Developments Of Novel Environmental Biotechnologies Via Microbial Stress Responses

Microorganisms live in changing environments with various stresses,which elicit phenotypic and genetic variations.Although the cellular stress responses and its underlying mechanisms have been intensively studied,seldom reports explored the possibilities of employing the microbial stress response in bioprocesses.As environmental biotechnologies mainly rely on the cell surface properties or metabolism of microorganisms for contaminant treatment,and these properties or physiology are largely influenced by environmental stress,we proposed that the cellular stress responses of microorganisms can be applied in biotechnology.In this study,Synechococcus elongats PCC7942,Microcystis aeruginosa and model hosts Escherichia coli were chosen as examples for this proof of principle research,we exerted external stress and employed sythetic biology to investigate whether the stress response mechanisms could be utilized for environmental benefits.The main conclusions are as follow:(1)We demonstrated that it is feasible to employ cellular stress responses of cyanobacteria induced by osmotic stress for enhanced biosorption.The enhanced biosorption is attributed to the induced stress responses which elicited the combined effects of exopolysaccharides over-secretion and the up-regulated carbonic anhydrase activity.The increased expression level of sigma factor further evidenced our hypothesis that the enhanced biosorption was induced via the physiological stress responses by exerting osmotic stress.These results indicated that the inducible physiological responses of microorganisms can be employed for enhanced environmental application.(2)In order to take advantage of targeted stress responses of microbes,we designed and introduced a genetic module harboring the tetracycline degrading gene tetX into the model host,Escherichia coli,and generated a prototypal whole-cell biodevice for degradation of target antibiotics.The strain degraded tetracycline efficiently via hydroxylation,and over 98%of the tetracycline was removed within 24 h.The detoxification capability of TetX protein encoded by tetX was also verified.These resultes suggested that the feasibility of introducing genetic modules to enable environmental functions in model hosts and also would inspire more environmental innovations through synthetic routines.