AUTHOR=Ungerfeld Emilio M. , Newbold C. Jamie TITLE=Editorial: Engineering Rumen Metabolic Pathways: Where We Are, and Where Are We Heading JOURNAL=Frontiers in Microbiology VOLUME=8 YEAR=2018 URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.02627 DOI=10.3389/fmicb.2017.02627 ISSN=1664-302X