Mining of novel chassis bacteria from the gut of dairy cows and construction of engineered bacteria

Engineered bacteria can efficiently produce a variety of bioactive substances with complex structures and diverse functions, which has great application value in animal breeding and industrial production. The development of engineered bacteria based on chassis derived from dairy cows is of theoretical significance and practical value for the promotion of healthy breeding in dairy cows through the utilisation of microorganisms. In order to construct cow engineered bacteria capable of secreting and expressing foreign proteins, the signal peptide pelB was connected to the target gene in order to modify the low-copy plasmid pBAD. The recombinant plasmid was transformed into Escherichia coli Nissle 1917 (EcN), and the secretion and expression efficiency of the plasmid were verified by SDS-PAGE and DNS enzyme activity assay method. A potential chassis bacterium, Escherichia coli E28, was isolated, cultured and screened from the faeces of healthy dairy cows using the limiting dilution method. Safety evaluation and genomic analysis indicate that it can be used as a new type of chassis bacterium. The recombinant vector was transformed into E28, and the target gene was successfully expressed in a secretory manner. In conclusion, the engineering of bacteria that can secrete and express foreign genes has been successfully constructed, providing a new model for the development of biological agents in animal husbandry in the future and a reference for the development of other important economic livestock chassis bacteria.