沼气池中的微生物所属成分是什么?急急急!

沼气池中的微生物所属成分是什么?急急急!
沼气池中的微生物所属成分是什么?急急急!

沼气池中的微生物所属成分是什么?急急急!
给你看篇英文文献吧 title：Taxonomic composition and gene content of a methane-producing microbial community isolated from a biogas reactor
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T3C-4ST3YB0-1&_user=1555949&_coverDate=08%2F31%2F2008&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1610706641&_rerunOrigin=scholar.google&_acct=C000053684&_version=1&_urlVersion=0&_userid=1555949&md5=6257014cbb722e1fce11c66cb1468634&searchtype=a
3. Results and discussions
3.1. Composition of the biogas-producing microbial community isolated from the first fermenter of an agricultural biogas plant
The composition of the biogas-producing microbial community was assessed using two complementary approaches: First, the taxonomic origins of reads were predicted by using 16S rDNAs as phylogenetic anchors. To get a more detailed picture of the taxonomic composition of the biogas reactor sample, in a second approach the CARMA software (Krause et al., 2008) was applied The main idea of CARMA is to identify gene fragments (EGTs) in community reads using Pfam profile hidden Markov models and to subsequently predict the taxonomic origins of these fragments by a phylogenetic analysis. Both approaches yielded a community-specific taxonomic profile portraying the composition of the underlying microbial community at each taxonomic rank (superkingdom, phylum, class, order, and genus).
3.1.1. Taxonomic composition inferred by a 16S rDNA analysis
Based on a Blast comparison of reads from the biogas reactor sample with the ARB database, 1930 16S rDNAs were identified with averaging length of 177 bp. For sequences of this length (100–200 bp) correct assignments are obtained using the RDP Classifier, with accuracy levels ranging from 99.2% to 99.7% for phylum to 74.9–86.6% for genus (Wang et al., 2007). Notably, the achieved accuracy may vary greatly, depending on whether conserved or hypervariable regions of 16S rDNAs are classified.
Bacteria are the dominant superkingdom in the biogas reactor: 82% of the 1930 identified 16S rDNAs were classified as Bacteria, only 2.5% were classified as Archaea, the remaining sequences are of unknown origin (Table 1). Firmicutes is the most abundant phylum (26% of 16S rDNAs), followed by Bacteroidetes and Euryarchaeota (3.7% and 2.4% of 16S rDNAs, respectively). Proteobacteria was not detected. At rank class, Clostridia (12%), Bacteroidetes (2.7%), and Methanomicrobia (2.3%) are overrepresented phylogenetic groups, at rank order Clostridiales (9%), Bacteroidales (2.7%), and Methanomicrobiales (2.3%). With 2.8% of assigned 16S rDNAs, Methanoculleus is the most abundant genus and dominant among the methanogens.
Table 1. Taxonomic characterization of a biogas reactor environmental sample (16S rDNA based)
Superkingdom
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1930
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Phylum
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620
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Class
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356
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Order
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287
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Genus
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90
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Archaea 48 Euryarchaeota 47 Methanomicrobia 45 Methanomicrobiales 45 Methanoculleus 44
Bacteria 1591 Actinobacteria 1 Actinobacteria 1 Actinomycetales 1 Tetrasphaera 1
Bacteroidetes 72 Bacteroidetes 53 Bacteroidales 53 Proteiniphilum 3
Petrimonas 2
Firmicutes 495 Bacilli 1 Lactobacillales 1
Clostridia 239 Clostridiales 172 Acetivibrio 4
Clostridium 4
Anaerovorax 1
Pelotomaculum 2
Sedimentibacter 6
Anaerobaculum 2
Syntrophomonas 6
Thermoanaerobacteriales 3 Tepidanaerobacter 2
Thermacetogenium 1
Mollicutes 12 Acholeplasmatales 6 Acholeplasma 6
Entomoplasmatales 1 Spiroplasma 1
Spirochaetes 2 Spirochaetes 2 Spirochaetales 2 Treponema 2
Thermotogae 3 Thermotogae 3 Thermotogales 3 Petrotoga 3
Unknown 291
Full-size table
The taxonomic origins of rDNAs can frequently not be inferred on lower taxonomic ranks. As a consequence, the sum of numbers at lower taxonomic ranks may differ from the sum at higher ranks. Shown are numbers of 16S rDNAs classified into each taxonomic group.
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3.1.2. EGT-based analysis of taxonomic composition
A similar picture of the composition of the biogas-producing microbial community was obtained by the phylogenetic classification of EGTs (gene fragments identified in community sequence reads) (Table 2). In 133,337 reads (22% of all reads) an EGT was identified. The majority of EGTs (68%) were classified as belonging to Bacteria and 11% as Archaea. A low proportion of EGTs was assigned to Eukaryota (4%) and viruses (0.4%), 16% of EGTs could not be assigned to any phylum. Despite the high consistency of the results produced by the two methods, some degree of variation was identified. While CARMA predicted that 15% of the prokaryotic fraction of EGTs (pEGTs) stems from Proteobacteria, none of the 16S rDNAs was assigned to this phylogenetic category. As a further discrepancy, only CARMA predicted Bacilli (6% of pEGTs). Within the Bacilli, Bacillales (3% of pEGTs) and Lactobacillales (2% of pEGTs) were predicted. The presence of bacilli is likely, since they may be introduced into the biogas reactor with maize silage and chicken manures.

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