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The DGGE analysis method may have specific limitations such as band crowding or malposition during the electrophoresis. The agreed primer of DGGE also can not cover or separate all kinds of bacteria. Occasionally, special classes cannot be discerned due to their migration to identical positions in the gel and thus further qualitative analysis needs to be taken. To understand the detailed community structure, 16s rRNA gene cloning library of the microbial community was established. The effect of the AT addition on the microbial functional diversity was investigated. The phylogenetic tree of the samples taken from the sDMBR with (SEUDM4) and without (SEUDM1) AT addition is shown in Figure 5 and Table 6. In total, there were nine phyla: α-Proteobacteria, β-Proteobacteria, γ-Proteobacteria, δ-Proteobacteria, Firmicutes, Acidobacteria, Bacteroidetes, Nitrospira and Planctomycete. In the phylum of the Firmicutes, the Lactococcus-like genus which contains Homofermentors species with a single product-lactic acid (Buyze et al. 1957) were detected in both SEUDM4 (four clones) and SEUDM1 (one clone). In the dominated phylum of β-Proteobacteria, 34 and 26 clones were detected inSEUDM4 and SEUDM1, respectively. There were eight clones of γ-Proteobacteria detected in SEUDM4 compared to 15 clones detected in SEUDM1. There were three and two clones of γ-Proteobacteria detected in SEUDM1 and SEUDM4, respectively. In the phylum of the Acidobacteria, two clones of SEUDM4 and one clone of SEUDM1 were detected as Acidobacteriaceae. In the phylum of Bacteroidetes, six clones were detected as Trachelomonas-like and Sphingobacteria-like in SEUDM1 and eight clones were detected in SEUDM4. There were 13 clones of uncultured-Bacterodetes-like in SEUDM1, but only one clone in SEUDM4 was detected. In total, 22 clones in SEUDM4 and 30 clones were detected in the phyla of Bacteroidetes. The nitrite-oxidizing bacteria were detected in both of the samples, which was important for nitrogen removal in the system and these belong to the genus of Nitrospira (Juretschko et al. 1998). Moreover, two clones of Planctomycete were detected in both of the samples. Among the Planctomycete (Strous et al. 1999), there were some unusual bacteria such as an ammox bacteria which contributed to the nitrogen cycle. Furthermore, the microbial community structure of the SEM proved to have high diversity cellular morphology in our previous study during the reactor start up (Duan et al. 2011c). All indices support our observation that microbial communities became more diverse after AT addition. Our previous study showed that a dense layer of porous dynamic film was formed on the non-woven surface with a high density of microbe. Similar results of a variety of microbes were found in the DMBR, such as Coccus, Bacillus, Chainlike Cocci, Filamentous bacteria, etc. (Fan & Huang 2002).
Table 6

Dominant microbial species in sDMBR with and without AT addition detected by high-density 16S rRNA microarray

 BandsNameNCBIIdentity (%)
sDMBR without AT addition SEUDM1 Gemmata SP GQ889432 99 
SEUDM1 Planctomycete Elev EF019893 97 
SEUDM1 Uncultured Nitrospira CU466689 98 
SEUDM1 Trachelomonas JN679099 98 
SEUDM1 Chitinophaga JN679126 99 
SEUDM1 Bacteroidetes CU924211 98 
SEUDM1 Columnare AY842901 97 
SEUDM1 Acidobacteria CU921213 97 
SEUDM1 Deltaprotebacterium DQ182112 96 
SEUDM1 Rheinheimera GQ284452 98 
SEUDM1 Gamma proteobacterium AM182112 99 
SEUDM1 Chromatiaceae EU640700 98 
SEUDM1 Acidovorax HQ704415 99 
SEUDM1 Resiniphila NR027188 98 
SEUDM1 Zoogloea JF808745 99 
sDMBR with AT addition SEUDM4 Rhodocyclaceae HQ184356 98 
SEUDM4 Betaproteobacterium CU456789 99 
SEUDM4 Zoogloeaorgzae AB201044 97 
SEUDM4 Comamonas GU257797 99 
SEUDM4 Methylibium JN217059 98 
SEUDM4 Azonexus JN125387 99 
SEUDM4 Dokdonella AB663505 99 
SEUDM4 Rhizosphere AJ252682 98 
SEUDM4 Aeromonas JF496528 99 
SEUDM4 Deltaproteobacterium GASP-MB2W 98 
SEUDM4 Flavobacterium SP HM638233 99 
SEUDM4 Sphingobacteriales JN679200 97 
SEUDM4 Bacteroidetes EU283376 99 
SEUDM4 Vanneervenii AJ966883 99 
SEUDM4 Planctomycete AY921761 98 
SEUDM4 Isosphaera GQ889467 99 
 BandsNameNCBIIdentity (%)
sDMBR without AT addition SEUDM1 Gemmata SP GQ889432 99 
SEUDM1 Planctomycete Elev EF019893 97 
SEUDM1 Uncultured Nitrospira CU466689 98 
SEUDM1 Trachelomonas JN679099 98 
SEUDM1 Chitinophaga JN679126 99 
SEUDM1 Bacteroidetes CU924211 98 
SEUDM1 Columnare AY842901 97 
SEUDM1 Acidobacteria CU921213 97 
SEUDM1 Deltaprotebacterium DQ182112 96 
SEUDM1 Rheinheimera GQ284452 98 
SEUDM1 Gamma proteobacterium AM182112 99 
SEUDM1 Chromatiaceae EU640700 98 
SEUDM1 Acidovorax HQ704415 99 
SEUDM1 Resiniphila NR027188 98 
SEUDM1 Zoogloea JF808745 99 
sDMBR with AT addition SEUDM4 Rhodocyclaceae HQ184356 98 
SEUDM4 Betaproteobacterium CU456789 99 
SEUDM4 Zoogloeaorgzae AB201044 97 
SEUDM4 Comamonas GU257797 99 
SEUDM4 Methylibium JN217059 98 
SEUDM4 Azonexus JN125387 99 
SEUDM4 Dokdonella AB663505 99 
SEUDM4 Rhizosphere AJ252682 98 
SEUDM4 Aeromonas JF496528 99 
SEUDM4 Deltaproteobacterium GASP-MB2W 98 
SEUDM4 Flavobacterium SP HM638233 99 
SEUDM4 Sphingobacteriales JN679200 97 
SEUDM4 Bacteroidetes EU283376 99 
SEUDM4 Vanneervenii AJ966883 99 
SEUDM4 Planctomycete AY921761 98 
SEUDM4 Isosphaera GQ889467 99 
Figure 5

Phylogenetic tree comparison of the two samples with and without AT addition.

Figure 5

Phylogenetic tree comparison of the two samples with and without AT addition.

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