Professor John Wallace - Microbial metabolism in the gut of man and ruminants

Research focus

Methane is a greenhouse gas (GHG), 25 times as potent as carbon dioxide. Ruminants are major methane emitters, contributing 3-4% of global GHG emissions. The methane is derived from microbial fermentation in the rumen, being produced by microbes known as archaea. The archaea convert hydrogen and carbon dioxide produced by bacteria and protozoa to methane. In our Theme 5 work funded by RESAS, the ruminal methanogenic archaea of Scottish cattle and sheep are being characterized, in collaboration with Bob Mayes of the James Hutton Institute and Rainer Roehe of the Scottish Agricultural College. We will assess whether high methane-producing animals possess a different archaeal community to low-methane producers, and dietary and/or host characteristics associated with the differences.

Hydrogen is also utilized by fatty acid biohydrogenation in the rumen, which leads to a high proportion of health-threatening saturated fatty acids in foods derived from ruminants and to the formation, followed by the destruction, of health-promoting conjugated linoleic acids (CLA), and to the destruction of n-3, health-promoting fatty acids. The primary aim of this part of our research is to improve the fatty acid composition of ruminant milk and meat for human health. In order to achieve this aim, the microorganisms responsible for fatty acid transformations in the rumen are being identified, the fluxes through pathways of biohydrogenation and desaturation measured, the population sizes of the most significant microbial species evaluated, and ways of altering these fluxes and populations are being investigated. If these objectives can be achieved, it will then be possible, using dietary manipulation or new feed additives, to improve the health profile of fatty acids in ruminant products.

Microbial metabolism in the gut of man has implications for health. In particular, the microbial degradation of protein in the distal colon leads to the formation of toxic products. If amino acids were to be assimilated rather than broken down, much less toxic material would be formed. Protein-rich, low-carbohydrate diets lead to higher genotoxic activity in the colon and to the enrichment of pathogens, including Clostridium perfringens. The factors leading to these developments are being investigated. The possible usefulness of essential oils in promoting gut health, via their effects on commensal as well as pathogenic bacteria, is being investigated in an industrially funded studentship (Mr Dinesh Thapa, Nepal).

I previously coordinated two EC-funded programmes, RUMEN-UP and REPLACE, whose aims were to find alternatives to growth-promoting antibiotics. The new 2012 FP7 project (7.7M euros) of which I am coordinator is named RuminOmics: Connecting the animal genome, gastrointestinal microbiomes and nutrition to improve digestion efficiency and the environmental impacts of ruminant livestock production (www.ruminomics.eu). Eleven partners across Europe will attempt to define the relations between host genetics, the ruminal microbiome and emissions using state-of-the-art –omics technologies. While doing so, we aim to develop tools for livestock producers and breeders to help them increase the efficiency of production by lowering polluting emissions.

I also participate in the FP7 FOODSEG project (foodseg.net) and the Global Research Alliance, which is a NZ initiative aiming to bring countries together to find ways to grow more food without growing GHG emissions. Recent Technology Strategy Board awards with Ingenza Ltd and Innovent Technology Ltd will enable metagenomic approaches to be taken to solve the methane problem, as well as to find new enzymes of industrial significance. In my spare time, I am on the Editorial Advisory Board of Animal Feed Science and Technology and participate in the Centre of Expertise, ClimateXChange.

Policy Briefings

• Plants and plant extracts to replace growth-promoting antibiotics in livestock production

Press Releases

13th Feb: New European study to investigate methane production in livestock

Latest Publications