title: High genetic diversity and different distributions of glycosyl hydrolase family 10 and 11 xylanases in the goat rumen.
abstract: BACKGROUND
  The rumen harbors a complex microbial ecosystem for efficient hydrolysis of plant polysaccharides which are the main constituent of the diet. Xylanase is crucial for hemicellulose hydrolysis and plays an important role in the plant cell wall degradation. Xylanases of ruminal strains were widely studied, but few studies have focused on their diversity in rumen microenvironment.
  
  
  RESULTS
  We explored the genetic diversity of xylanases belonging to two major glycosyl hydrolase families (GH 10 and 11) in goat rumen contents by analyzing the amplicons generated with two degenerate primer sets. Fifty-two distinct GH 10 and 35 GH 11 xylanase gene fragments (similarity <95%) were retrieved, and most had low identities with known sequences. Based on phylogenetic analysis, all GH 10 xylanase sequences fell into seven clusters, and 88.5% of them were related to xylanases from Bacteroidetes. Five clusters of GH 11 xylanase sequences were identified. Of these, 85.7% were related to xylanases from Firmicutes, and 14.3% were related to those of rumen fungi. Two full-length xylanase genes (one for each family) were directly cloned and expressed in Escherichia coli. Both the recombinant enzymes showed substantial xylanase activity, and were purified and characterized. Combined with the results of sheep rumen, Bacteroidetes and Firmicutes are the two major phyla of xylan-degrading microorganisms in rumen, which is distinct from the representatives of other environments such as soil and termite hindgut, suggesting that xylan-degrading microorganisms are environment specific.
  
  
  CONCLUSIONS
  The numerous new xylanase genes suggested the functional diversity of xylanase in the rumen microenvironment which may have great potential applications in industry and agriculture. The phylogenetic diversity and different distributions of xylanase genes will help us understand their roles in plant cell wall degradation in the rumen microenvironment.
authors.affiliation: Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing, People's Republic of China.
authors.forename: Guozeng
authors.initials: G
authors.lastname: Wang
authors.forename: Huiying
authors.initials: H
authors.lastname: Luo
authors.forename: Kun
authors.initials: K
authors.lastname: Meng
authors.forename: Yaru
authors.initials: Y
authors.lastname: Wang
authors.forename: Huoqing
authors.initials: H
authors.lastname: Huang
authors.forename: Pengjun
authors.initials: P
authors.lastname: Shi
authors.forename: Xia
authors.initials: X
authors.lastname: Pan
authors.forename: Peilong
authors.initials: P
authors.lastname: Yang
authors.forename: Qiyu
authors.initials: Q
authors.lastname: Diao
authors.forename: Hongfu
authors.initials: H
authors.lastname: Zhang
authors.forename: Bin
authors.initials: B
authors.lastname: Yao
mesh_terms: D000818:Animals; D001439:Bacteroides / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D003001:Cloning, Molecular; D014644:Genetic Variation / Q000502:physiology; D006026:Glycoside Hydrolases / Q000235:genetics / Q000378:metabolism; D006041:Goats / Q000235:genetics* / Q000378:metabolism* / Q000382:microbiology; D008954:Models, Biological; D008969:Molecular Sequence Data; D005810:Multigene Family; D010802:Phylogeny; D018720:Prevotella / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D012417:Rumen / Q000201:enzymology* / Q000378:metabolism / Q000382:microbiology; D014018:Tissue Distribution; D014995:Xylosidases / Q000235:genetics / Q000378:metabolism
chemical_list: D006026:Glycoside Hydrolases; D014995:Xylosidases