Gut microbes in cows and hoatzins
In order to effectively access the energy stored in vegetation, cows and other ruminants have an enlarged foregut that contains a variety of microbes that aid in the breakdown of the otherwise indigestible plant matter through fermentation. Interestingly this trait is not only common to various mammals including cows, sheep, deer, and sloths but is also present in the hoatzin, a folivorous bird that feeds on young plant leaves. The presence of foregut fermentation in both cows and hoatzins is an example of evolutionary convergence that Dr. Filipa Godoy-Vitorino and her colleagues in a team lead by Dr. Maria Gloria Dominguez-Bello used to answer the question of whether host phylogeny or organ function contributes to the evolution of gut microbial communities.
In their study, published recently in the ISME Journal, Dr. Godoy-Vitorino and her colleagues used PhyloChip to analyze the microbes present in the foreguts and hindguts of four cows and four hoatzins. The team chose to use PhyloChip as it is “a fast and economic way to compare profiles of microbiota between different ecosystems.” The results indicated that there was “a clear 'core' microbiota for the foregut organs and a 'core' microbiota for the hindgut organs, regardless of the independent origin of foregut fermentation in birds and mammals.” This core microbiota for the foregut included populations of Bacteriodetes, Acidobacteria, and Spriochaetes but fewer Proteobacteria and Firmicutes than the hindgut. In addition to the core microbiota there were a variety of other microbes present with the cow digestive organs containing a higher number of species than the hoatzin. There were also microbes that were present only in the foreguts and not in the hindguts including various Bacteriodetes, Cyanobacteria, Lentisphaerae, Planctomycetes, and Spirochaetes species. A broad UniFrac comparison between hoatzins, cows and various other ruminants and birds showed that the hoatzin microbiota is “more similar to that of foregut fermenter mammals than to organs from other birds.”
As Dr. Godoy-Vitorino says “our study clearly shows that organ function is a stronger determinant of microbial community structure than host phylogeny. Despite the phylogenetic distance of the hosts (bird and mammal), the fact that they have a similar digestive strategy, their fermentative organs play similar roles and thus we find 'core' taxa in all of them.” As the next step in their research the team is currently analyzing the metagenome of the hoatzin foregut in order to create an inventory of the genes present. The identification of genes present in foregut fermenters is potentially useful to the biofuel industry. As Dr. Godoy-Vitorino points out, “to stop our dependency in fossil fuels we might be able to modify bacteria to express carbohydrate-active enzymes (found for example in the hoatzin or cows) to degrade, wood, paper, etc., to the ultimate production of alcohol to be used as alternative source of energy.”
Article:
Filipa Godoy-Vitorino, Katherine C Goldfarb, Ulas Karaoz, Sara Leal, Maria A Garcia-Amado, Philip Hugenholtz, Susannah G Tringe, Eoin L Brodie, and Maria Gloria Dominguez-Bello. (2011). Comparative analyses of foregut and hindgut bacterial communities in hoatzins and cows. The ISME Journal, advance online publication, 22 September 2011.
DOI: 10.1038/ismej.2011.131
About the author: Ruth Warre is a freelance scientific writer and editor currently living in Toronto. She writes on a variety of subjects from microbiomes to neuroscience, in a variety of mediums from blogs to peer-reviewed articles.
