Engineering Ruminal Flora for Improved Protein Quality

Summary

Rumen bacteria are being manipulated genetically to introduce genes encoding high quality proteins containing a balance of essential amino acids. Several hybrid gene constructs have been prepared comprising gene sequences encoding essential amino acids inserted into a protein carrier. Some of these have been cloned and expressed in E. coli. Plasmid and bacteriophage vectors have been constructed to allow gene transfer to the rumen bacteria Bacteroides and Selenomonas respectively. The bacteriophage vector has been genetically mapped and critical regions have been defined. Transformation of Selenomonas has been achieved using two different methods with a frequency of up to 5 × 10² transformants/μg of DNA. The procedure has been optimised for Selenomonas and the technique will form the basis of a general transformation system for gene transfer in other species of rumen microorganisms.