Abstract
BackgroundThe newly proposed methanogenic order ‘Methanomassiliicoccales’ is the second largest archaeal population in the rumen, second only to the Methanobrevibacter population. However, information is limited regarding the community of this new order in the rumen.MethodsThis study used real-time PCR and 454 pyrosequencing to explore the abundance and community composition of Methanomassiliicoccales in the rumen of Chinese goats fed a hay (0% grain, n = 5) or a high grain (65% grain, n = 5) diet.ResultsReal-time PCR analysis showed that the relative abundance of Methanomassiliicoccales (% of total archaea) in the goat rumen was significantly lower in the high-grain-diet group (0.5% ± 0.2%) than that in the hay-diet group (8.2% ± 1.1%, P < 0.05). The pyrosequencing results showed that a total of 208 operational taxonomic units (OTUs) were formed from ten samples at 99% sequence identity. All the sequences were identified as Methanomassiliicoccaceae at the family level, and most of the sequences (96.82% ± 1.64%) were further classified as Group 8, 9, and 10 at the Methanomassiliicoccales genus level in each sample based on the RIM-DB database. No significant differences were observed in the number of OTUs or Chao1’s, Shannon’s or Pielou’s evenness indexes between the hay- and high-grain-diet groups (P ≥ 0.05). PCoA analysis showed that diet altered the community of Methanomassiliicoccales. At the genus level, the relative abundances of Group 10 (67.25 ± 12.76 vs. 38.13 ± 15.66, P = 0.012) and Group 4 (2.07 ± 1.30 vs. 0.27 ± 0.30, P = 0.035) were significantly higher in the high-grain-diet group, while the relative abundance of Group 9 was significantly higher in the hay-diet group (18.82 ± 6.20 vs. 47.14 ± 17.72, P = 0.020). At the species level, the relative abundance of Group 10 sp. (67.25 ± 12.76 vs. 38.13 ± 15.66, P = 0.012) and Group 4 sp. MpT1 (2.07 ± 1.30 vs. 0.27 ± 0.30, P = 0.035) were significantly higher in the high-grain-diet group, while the relative abundance of Group 9 sp. ISO4-G1 was significantly higher in the hay-diet group (12.83 ± 3.87 vs. 42.44 ± 18.47, P = 0.022).ConclusionsOnly a few highly abundant phylogenetic groups dominated within the Methanomassiliicoccales community in the rumens of Chinese goats, and these were easily depressed by high-grain-diet feeding. The relatively low abundance suggests a small contribution on the part of Methanomassiliicoccales to the rumen methanogenesis of Chinese goats.
Highlights
The newly proposed methanogenic order ‘Methanomassiliicoccales’ is the second largest archaeal population in the rumen, second only to the Methanobrevibacter population
The relative abundance of Methanomassiliicoccales in the goat rumen as measured via real-time PCR The real-time PCR results showed that the relative abundance of Methanomassiliicoccales in the rumen of goats fed the hay diet was 8.20% ± 2.43%, which was higher than that (0.50% ± 0.38%) in the rumen of goats fed the high-grain diet (P = 0.002)
Across all reads from the ten samples, a total of 208 operational taxonomic units (OTUs) were formed after the removal the OTUs containing less than ten sequences
Summary
The newly proposed methanogenic order ‘Methanomassiliicoccales’ is the second largest archaeal population in the rumen, second only to the Methanobrevibacter population. A large group of archaea closely related to the Thermoplasmatales has been proposed as a new methanogenic order ‘Methanomassiliicoccales’ [1, 2]. Methanomassiliicoccales accounted for less than 5% of the archaea in the rumens of sheep, water buffalo, yaks, dairy cattle, and other ruminant species [5]. Seedorf et al [6] used 454 pyrosequencing to study the methanogenic communities in the rumens of New Zealand sheep and cattle fed with pasture (ryegrass and white clover). They reported a mean relative abundance of Methanomassiliicoccales of about 10.4%, but this value exceeded 40% in some treatment groups [6]. Methane is produced by via the hydrogenmediated reduction of methyl-group-containing compounds (e.g., methylamines and methanol) [8,9,10]
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