Rumen-like methanogens identified from the crop of the folivorous South American bird, the hoatzin (Opisthocomus hoazin)

Abstract

The hoatzin is the only known avian species with foregut fermentation. It is a primarily folivorous feeder and has a distended crop and lower/distal esophagus, which has evolved for the microbial fermentation of ingested feed. Crop samples collected from 10 individual animals from the Apure River area, Apure State, Venezuela were examined for the presence and density of methanogens using 16S rRNA gene clone libraries and real-time PCR prepared from pooled and individual PCR products. A total of 197 clones were examined, revealing 24 different methanogen 16S rRNA sequences, or phylotypes. Of the 24 unique phylotypes, 16 (171 of 197 clones) formed five unique clades within the genus Methanobrevibacter with the largest group of clones (118 clones) 98.7% similar to Methanobrevibacter ruminantium. The remaining eight phylotypes (26 clones) formed four unique clades that had only 94.0-96.7% identity to Methanosphaera stadtmanae. Based upon 98% sequence identity, we identified 17 of the 24 methanogen phylotypes from the hoatzin as possible new species and strains, with three phylotypes representing possible new genera (o94.5% sequence identity). Although none of the hoatzin methanogen phylotypes had 100% sequence identity to any other archaeal sequences in the GenBank database, the hoatzin crop methanogen sequences formed sister groups with known rumen methanogens. Mean population densities (numbers per gram wet weight) of methanogenic archaea, rumen bacteria and ciliate protozoa, estimated using real-time PCR, were 5.80 Â 10 9 , 7.93 Â 10 12 and 3.31 Â 10 5 , respectively. The crop microbial data presented here provide an excellent example of convergent evolution of foregut fermentation in the hoatzin, similar to that of ruminants.

Examination of the Rumen Bacteria and Methanogenic Archaea of Wild Impalas (Aepyceros melampus melampus) from Pongola, South Africa

“…In the present study, Methanobrevibacter species were the most dominant methanogens from the four impalas, similar to previous studies on a range of host species including Mediterranean water buffalo on three different diets in Brazil, sheep from Venezuela, sheep from Western Australia on three different diets, lambs on different high-grain diets in France, lactating Jersey and Holstein cows in Vermont, alpaca from Vermont, and in the Hoatzin from South America [24,26,[41][42][43][44][45]. However, at the species level, the majority of the 16S rRNA gene sequence reads from the highest represented OTU had the highest sequence identity to M. thaueri, a methanogen first isolated from cow feces and a member of the Methanobrevibacter smithii-gottschalkii-millerae-thaueri (SGMT) clade that uses hydrogen and carbon dioxide to produce methane [24,46].…”

Diversity of gut methanogens in herbivorous animals

“…The hoatzin (Opisthocomus hoazin), a follivorous bird from South America, is the only bird species to have evolved a foregut fermentation system, the crop, that is analogous to the rumen. Methanobrevibacter ruminantium was the highest represented methanogen (64.5%) in the crop of the hoatzin, followed by a substantial representation of unassigned Methanobrevibacter species (21.3%) and unassigned Methanosphaera species (13.2%; Wright et al, 2009). In chickens, Methanobrevibacter woesei was found to be the most prevalent methanogen in the ceaca (96.7%; Saengkerdsub et al, 2007).…”

Methanogens and Methanogenesis in the Rumens and Ceca of Lambs Fed Two Different High-Grain-Content Diets

“…MEGA 5 (25) was used to compute distance matrixes for both mcrA-Luton sequences (using the Kimura 2-parameter algorithm) and MCR-Luton sequences (using the Dayhoff model). We used different species cutoff limits (unique and from 0.01 to 0.06) for rrs in MOTHUR and confirmed for this data set that 0.02 (98% similarity) was the best-adapted value to define archaeal species as previously reported (26). Pairwise comparisons of mcrA-Luton and MCR-Luton fragments and rrs sequences were performed to calculate the nucleotide or amino acid difference and then the percent sequence identity.…”