Out of the black box and back to the future: New frontiers and challenges for rumen microbiology to advance animal growth and development.

Ruminant microbiology has been studied for more than a century, initially via microscopic examinations of rumen fluid providing morphological and compositional descriptions of the microbiota. Cultivation techniques for obligate anaerobes were developed in the mid-20th Century, and the principal way of studying rumen microbiology shifted, to culture and isolate as many species as possible then study select physiological processes. In the late ‘80s and ‘90s, with the development of tools such as PCR, and the application of reverse transcriptase and DNA polymerases, the field of rumen microbial ecology was transformed to a largely cultivation-independent field of inquiry, using 16S rRNA and/or the gene encoding that molecule as a semantide. During this period, recombinant DNA technologies also made an impact on the field of rumen microbiology, principally via a level of reductionism that provided deeper knowledge about fewer rumen microbial interactionsand processes. In the first decade of the 21st Century, microbialbiology has advanced from the sequencing of individual genomes, to comprehensive assessments of microbial diversity and the genetic potential resident within entire microbial communities. This has been driven largely by the appreciation that culturable microbes represent only a small percentage of the microbial world and advances in high throughput sequencing technologies. As such, there has been a renewed interest in the interrogation of rumen and other gut microbiomes via (meta)genomic approaches. So, are these efforts resulting in more of the same, or something “new” in relation to our understanding of the microbial biology underpinning rumen function, nutrient availability, and animal growth and development; and from which, new opportunities might emerge? This presentation will examine some of the latest observations and findings arising from the study of individual rumen bacteria, as well as rumen microbiomes. The field of rumen microbiologystill has something to offer the animal industries, as well as other sectors of science and industry