1. INTRODUCTION
4.3. Results and discussions
4.3.3. Microbial community dynamics
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Figure 4-6. XRD profile of the RM digestate taken on day 389 (at 8 mM magnetite).
74
community in both reactors. By contrast, the relative abundance of Spirochaetes (OTUs B2 and B8) increased significantly in both DNA and RNA libraries with the addition of magnetite or FeCl2 into the reactors. Therefore, it is likely that the growth and activity of Spirochaetes bacteria were significantly enhanced by either of the Fe compounds. The discrepancy between the DNA- and RNA-based analysis results is attributed to the difference between the abundance and metabolic activity of the individual populations (Baek et al., 2017), although the high variability of rRNA operon copy number in prokaryotes may also have had an effect (Hein et al., 2014).
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Figure 4-7. Relative abundance of bacterial sequences in the 16S rRNA gene and 16S rRNA libraries for RM, RC (A), RM1, and RM2 (B). Each lane is labeled with its corresponding reactor name and iron dose (mM Fe; magnetite for RM, RM1, and RM2, and FeCl2 for RC). Sequences with relative abundance lower than 1% in all samples were classified as “Others”.
The retrieved bacterial 16S rRNA gene sequences belonged to 23 known phyla, with 1.9% of them being unclassified at the phylum level. Bacteroidetes, Proteobacteria, Chloroflexi, Firmicutes, and Spirochaetes were the major phyla in both RM1 and RM2 (Fig. 4-7B). In RM1 and RM2, the changes in relative abundance of several bacterial phyla to the magnetite addition were similar with those observed in RM (Fig. 4-7A). For example, the growth and metabolic activity of Spirochaetes and Fibrobacteres bacteria were promoted by magnetite addition, showing increased relative abundance at both DNA and RNA levels, as in RM. Notably, the relative abundance of Bacteroidetes (particularly OTU B1, B2, and B3) greatly increased with magnetite addition, especially at the RNA level. Such remarkable increases in Bacteroidetes at magnetite-added conditions were largely accounted for by the genus Paludibacter (OTU B1), suggesting that their metabolic activity was enhanced by magnetite and likely affected the reactor performances in RM1 and RM2.
Looking at class Deltaproteobacteria, to which most SRBs belong (Rabus et al., 2006), two bacterial genera Desulfobulbus (OTU B6 in RM and RC, and OTU B6 in RM1 and RM2) and Desulfomicrobium (OTU B13 in RM and RC, and OTU B6 in RM1 and RM2) were likely the dominant SRBs in all reactors (Fig. 4-8). They were prevalent throughout the experiment at the RNA level as well as at the DNA level in both reactors. This result indicates that microbial sulfate reduction was active regardless of the addition of magnetite or FeCl2, further supporting the inference made above that S0 formation in the magnetite-added reactors (i.e., RM, RM1, and RM2) occurred through the oxidation of sulfide and not through the partial reduction of sulfate.
Anoxygenic phototrophic bacteria, such as purple sulfur bacteria, purple non-sulfur bacteria, and green sulfur bacteria, use sulfide as an electron donor for photosynthetic growth, and they produce S0 under anaerobic conditions (Frigaard, 2016). However, it is unlikely that the phototrophic oxidation of sulfide was active in four reactors, which were operated under dark conditions. Some chemotrophic bacteria, such as Sulfurospirillum, Desulfurispirillum, Wolinella, Beggiatoa, Thioploca, and Thiomagarita, anaerobically oxidize sulfide to S0; however, they need nitrate as an electron acceptor for anaerobic sulfide oxidation (Shao et al., 2010; Sorokin et al., 2007). In AD processes, nitrogen is present mostly as ammonium and in low amounts as nitrate (<4 mg NO3–-N/L
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throughout the experiment in four reactors); thus, sulfide oxidation coupled with nitrate reduction is unlikely in the experimental reactors. It is therefore inferred that unknown anaerobic sulfide- oxidizing bacteria (ASOBs) other than those mentioned above may have caused the microbial oxidation of sulfide to S0 in magnetite-added reactors. Accordingly, none of the OTUs were affiliated with the phototrophic or nitrate-reducing ASOBs described above.
Figure 4-8. Relative abundance of Deltaproteobacteria sequences in the 16S rRNA gene and 16S rRNA
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libraries RM, RC (A), RM1, and RM2 (B). Each lane is labeled with its corresponding reactor name and iron dose (mM Fe; magnetite for RM, RM1, and RM2, and FeCl2 for RC). Sequences with relative abundance lower than 1% in all samples were classified as “Others”.
The order Methanomicrobiales and the family Methanotrichaceae, particularly the latter, dominated the archaeal community in RM and RC (Fig. 4-9). In RM, the relative abundance of Methanosaetaceae (mainly OTU A1) increased greatly while that of Methanomicrobiales (mainly OTU A3) decreased with the addition of magnetite at both the DNA and RNA levels.
Methanotrichaceae accounted for 79.3% and 95.0% of the total archaeal sequences in the DNA and RNA libraries, respectively, at the magnetite dose of 20 mM Fe. By contrast, such an increase in Methanotrichaceae was not induced by the addition of FeCl2 at either the DNA or RNA level in RC.
It is therefore likely that magnetite addition somehow promoted the growth and metabolic activity of Methanotrichaceae in RM. The relative abundance of Methanotrichaceae at the RNA level in RC remained high (around 80%), although it is lower than that in RM before and after the addition of FeCl2. These results suggest that Methanotrichaceae played the main role in methanogenesis in both reactors.
Meanwhile, in both RM1 and RM2, the relative abundance of family Methanotrichaceae greatly decreased whereas that of order Methanobacteriales and Methanomicrobiales increased at DNA level in the presence of magnetite (Fig. 4-9B). At the magnetite dose of 20 mM Fe, Methanotrichaceae, Methanobacteriales, and Methanomicrobiales accounted for 17.0%, 22.8%, and 50.8% of the total archaeal sequences in DNA libraries. Such increases in hydrogenotrophic methanogens (i.e., Methanobacteriales, and Methanomicrobiales) in the presence of magnetite were recently reported (Baek et al., 2016; Li et al., 2015). However, such abundance profile at DNA level was totally different in that at RNA level. For example, Methanotrichaeceae was the predominant methanogen, which accounted for 85.9–91.3% of the total archaeal sequences in RNA libraries, and the relative abundance of Methanobacteriales and Methanomicrobiales occupied relatively low fractions (7.1–11.0% for Methanobacteriales and 0.0–0.6% for Methanomicrobiales). These indicate that the magnetite addition promoted the metabolic activity of Methanotrichaeceae as in RM, even though their abundance decreased at DNA level. Although Methanotrichaeceae was the most abundant methanogen in both reactors regardless of magnetite, the different members of Methanotrichaeceae contributed to their abundance in different experimental phases, particularly at RNA level. When magnetite was not added, OTU A1 was the major Methanotrichaceae in both reactors, whereas the abundance of Methanotrichaceae was primarily contributed by OTU A2 after
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magnetite addition (Table 4-7). This suggests that magnetite addition somehow fostered the metabolic activity of the specific Methanotrichaceae species in both experimental reactors.
Figure 4-9. Relative abundance of archaeal sequences in the 16S rRNA gene and 16S rRNA libraries for RM, RC (A), RM1, and RM2 (B). Each lane is labeled with its corresponding reactor name and iron dose (mM Fe; magnetite for RM, RM1, and RM2, and FeCl2 for RC). Sequences with relative abundance lower than 1% in all samples were classified as “Others.”.
The cluster dendrograms generated based on the rRNA gene and rRNA OTU abundances reflect the dynamic changes in the structure and activity of the reactor microbial communities across the experimental phases (Figs. 4-10 and 4-11). For RM and RC, the result indicates that the
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addition of magnetite or FeCl2 significantly influenced the evolution of both bacterial and archaeal communities in RM and RC and ultimately the reactor performance (Fig. 4-10). The cluster dendrograms clearly show that the community structure and activity in RM changed progressively as the magnetite dose increased, further demonstrating the significant effect of magnetite on the microbial ecology and performance of the reactor. The effect of the addition of Fe compounds is notably more apparent in the archaeal cluster dendrograms, particularly the one on the rRNA libraries. This finding appears to be attributable to the less diverse and less dynamic nature of archaea, most of which are methanogens with a narrow substrate range, compared with the bacteria in AD systems (Kim & Lee, 2015a). The effect on magnetite addition on microbial communities was also well presented in the cluster dendrograms of RM1 and RM2 (Fig 4-11). In the dendrograms based on both rRNA gene and rRNA libraries, both bacterial and archaeal community structures were largely grouped regarding magnetite addition. This confirmed again that the magnetite addition apparently affected the development of microbial community structure and consequently their activities.
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Table 4-6 Relative abundance and taxonomic affiliation of major archaeal and bacterial OTUs (>2% relative abundance in at least one sample)a.
OTU Classificationb
16S rRNA gene libraries 16S rRNA libraries
Closest cultivated speciesc
Accession number
Sim (%)d
RM RC RM RC
0 4 8 12 20 0 8 0 4 8 12 20 0 8
A1 Methanothrix 13.6 55.9 37.3 70.6 78.0 36.3 44.8 31.4 77.9 69.0 78.9 90.5 40.2 75.0 Methanosaeta concilii KF431940 97.6 A2 Methanothrix 11.9 4.6 1.0 3.0 1.2 31.3 1.9 32.8 10.4 6.8 13.4 4.4 35.3 4.3 Methanosaeta concilii KM408635 98.6 A3 Methanolinea 27.0 32.2 57.4 22.7 16.2 9.7 51.6 6.2 4.9 18.7 4.0 3.5 2.6 19.8 Methanolinea mesophila NR112799 95.9 A4 Methanospirillum 0.0 0.0 0.0 0.1 0.0 6.0 0.1 0.0 0.0 0.0 0.1 0.2 13.1 0.2 Methanospirillum
stamsii NR117705 97.9 A5 Euryarchaeota 5.9 1.2 1.6 0.7 0.5 0.8 0.2 5.6 1.3 4.5 1.9 0.8 0.3 0.5 Methanobrevibacter sp.
HW23 AB033293 87.7
A6 Euryarchaeota 20.8 1.9 0.0 0.0 0.0 0.3 0.0 16.7 1.4 0.0 0.1 0.0 0.1 0.0 Methanobrevibacter sp.
AbM23 KF697723 86.6
A7 Methanomassiliicoccus 0.3 0.5 0.3 0.5 1.4 6.2 1.0 0.9 3.3 0.2 0.5 0.3 4.4 0.2 Methanomassiliicoccus
luminyensis NR118098 93.8 A8 Methanoregulaceae 4.2 2.0 0.0 0.0 0.0 0.0 0.0 1.2 0.4 0.0 0.0 0.0 0.0 0.0 Methanolinea mesophila NR112799 95.2 A9 Methanobacterium 10.3 1.3 0.1 0.3 0.7 1.7 0.0 0.5 0.1 0.0 0.0 0.0 0.0 0.0 Methanobacterium
subterraneum CP017768 97.6
A10 Thermoprotei 4.1 0.1 2.0 0.8 0.5 0.5 0.0 1.8 0.2 0.7 0.7 0.1 0.1 0.0 Ca. Bathyarchaeota MH268291 97.8
A11 Methanolinea 0.0 0.0 0.1 0.1 0.0 5.1 0.0 0.0 0.0 0.1 0.0 0.0 3.7 0.0 Methanolinea tarda KP109880 97.9
A12 Methanothrix 1.6 0.0 0.0 0.0 0.0 0.0 0.0 2.6 0.1 0.0 0.0 0.0 0.1 0.0 Methanosaeta
harundinacea CP003117 98.6
B1 Paludibacter 11.5 19.7 1.5 6.5 14.7 12.2 8.5 36.3 36.1 8.7 44.7 32.3 45.8 24.0 Paludibacter sp. XHN03 MG763127 98.6 B2 Sphaerochaeta 0.5 0.1 5.8 2.7 15.9 0.8 15.7 2.3 0.4 31.3 17.9 35.2 3.0 38.8 Spirochaeta sp. JC231 LN614382 82.5
B3 Chloroflexi 0.8 8.3 18.5 22.1 11.2 11.2 5.3 0.3 1.4 0.5 0.6 0.0 0.3 0.1 Longilinea sp. AK5 MG734887 90.9
B4 Paludibacter 0.2 0.1 6.5 0.9 0.2 0.3 0.6 0.1 0.0 22.6 1.8 0.1 0.4 0.2 Paludibacter sp. XHN03 MG763127 93.8
B5 Bacteroidetes 10.8 4.0 2.8 3.4 2.7 2.3 0.0 2.7 0.4 3.4 4.2 1.4 1.4 0.0 Mariniphaga sp. KR012276 91.4
81
JXH-287
B6 Desulfobulbus 0.4 1.5 2.3 3.2 2.3 1.0 2.7 4.0 10.1 0.8 1.8 3.1 0.5 3.0 Desulfobulbus
propionicus MF623798 98.3
B7 Bacteroidetes 0.0 0.0 5.3 3.7 0.6 0.0 5.1 0.0 0.0 5.6 4.3 0.4 0.0 3.6 Lentimicrobium
saccharophilum NR149795 93.5
B8 Treponema 0.8 0.4 4.3 2.1 5.3 7.6 2.5 1.2 0.3 1.5 1.0 1.3 7.7 1.3 Treponema zuelzerae NR104797 98.3
B9 Bacteroidetes 13.7 0.1 0.0 0.0 0.0 0.0 0.0 18.0 0.0 0.0 0.0 0.0 0.0 0.0 Mangroviflexus
xiamenensis KT183419 93.7 B10 Fibrobacter 0.1 0.1 0.2 0.2 0.9 0.6 0.2 0.2 0.1 3.0 1.6 2.5 1.6 0.8 Fibrobacter sp. UW_T1 KY463366 90.8 B11 Saccharofermentans 1.4 2.8 1.1 3.6 3.9 2.7 0.0 0.6 0.3 0.0 0.0 0.0 0.0 0.0 Ercella succinigenes HG003577 97.9 B12 Saccharofermentans 0.2 0.4 3.5 3.1 2.7 2.6 0.3 0.1 0.1 0.1 0.1 0.1 0.0 0.2 Saccharofermentans
acetigenes AB910750 95.9
B13 Desulfomicrobium 0.4 0.6 1.3 2.1 0.6 2.9 1.5 0.4 0.1 1.0 1.9 0.4 2.6 3.3 Desulfomicrobium
norvegicum LS997916 98.6
B14 Clostridiales 0.2 1.4 1.8 1.7 0.5 0.1 8.3 0.1 0.4 0.1 0.0 0.0 0.0 0.3 Moorella humiferrea NR108634 86.6
B15 Bellilinea 0.0 0.1 13.5 5.3 0.6 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 Ornatilinea apprima NR109544 90.1
B16 Bacteroides 0.4 9.6 0.0 0.0 0.0 2.0 0.3 0.1 3.5 0.1 0.2 0.2 6.5 1.5 Bacteroides
graminisolvens MG859671 98.6 B17 Ca. Cloacamonase 10.0 3.7 0.0 0.0 0.1 0.0 0.5 8.3 2.7 0.0 0.0 0.0 0.0 0.2 Ca. Cloacamonas
acidaminovorans CU466930 98.6
B18 Smithella 0.8 0.7 0.6 0.4 1.1 0.2 0.1 2.7 0.8 3.3 1.6 3.0 1.1 0.4 Smithella propionica NR024989 95.5
B19 Sulfurovum 7.9 0.0 0.8 2.5 1.1 0.6 0.0 1.1 0.0 0.0 0.1 0.1 0.0 0.0 Sulfurovum
lithotrophicum CP011308 95.5
B20 Bacteroidetes 0.0 0.0 0.5 0.2 0.0 0.5 11.5 0.0 0.0 0.5 0.1 0.0 0.2 5.0 Lentimicrobium
saccharophilum NR149795 93.1
B21 Bacteroidetes 0.0 0.4 0.0 0.0 0.2 5.2 0.0 0.0 0.5 0.1 0.0 0.3 4.7 0.0 Lentimicrobium
saccharophilum NR149795 91.1
B22 Syntrophaceae 0.1 0.7 0.2 0.2 0.2 0.2 0.2 0.8 4.1 1.9 1.8 0.5 2.8 1.0 Syntrophus
aciditrophicus NR102776 95.2
82
B23 Firmicutes 1.9 3.8 2.7 2.4 1.3 4.5 0.5 0.2 0.4 0.4 0.5 0.1 0.2 0.1 Caldalkalibacillus
uzonensis NR043653 88.3
B24 Bacteroidetes 0.0 0.1 0.3 0.3 3.2 3.0 0.0 0.0 0.1 0.2 0.3 0.7 1.4 0.0 Saccharicrinis
fermentans MG264242 89.0
B25 Anaerolineaceae 0.0 0.0 2.0 4.2 0.9 0.0 0.6 0.0 0.0 0.2 0.3 0.0 0.0 0.0 Ornatilinea apprima NR109544 91.4
B26 Holophagaceae 0.3 0.4 0.0 0.5 0.3 4.5 0.3 0.3 0.3 0.1 0.5 0.3 5.9 0.4 Holophaga foetida NR036891 94.8
B27 Bacteria 0.0 2.0 0.0 0.0 0.0 0.0 0.0 0.0 10.3 0.0 0.0 0.0 0.0 0.0 Ca. Kuenenia
stuttgartiensis MH581480 83.8
B28 Pirellula 0.0 0.2 0.2 0.4 1.0 0.1 0.0 0.0 2.5 0.9 0.9 2.1 0.6 0.0
Ca.
Anammoximicrobium moscowii
KC467065 95.9
B29 Syntrophaceae 0.0 0.3 0.0 0.1 0.1 0.0 0.5 0.0 1.6 0.1 1.9 0.5 0.1 3.3 Smithella propionica NR024989 94.2 B30 Aminobacterium 1.4 0.1 0.3 0.4 2.3 0.1 1.5 0.6 0.0 0.1 0.1 0.3 0.0 0.4 Selenomonas sputigena KF528158 97.3 B31 Bacteroidetes 0.1 0.0 0.0 0.0 3.4 0.8 0.0 0.0 0.0 0.0 0.0 2.3 0.3 0.0 Solitalea canadensis KF528157 98.6 B32 Sunxiuqinia 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 5.0 0.0 0.0 Labilibacter aurantiacus NR156071 91.8
B33 Pseudomonas 1.2 0.0 0.0 0.0 0.0 0.0 0.2 6.0 0.0 0.1 0.0 0.0 0.0 0.1 Pseudomonas veronii MG972913 98.3
B34 Bacteroidetes 0.0 0.0 0.2 0.2 0.0 0.0 0.0 0.0 0.0 2.9 1.0 0.1 0.0 0.2 Riemerella anatipestifer MK641456 91.4
B35 Bacteroidetes 0.2 2.1 0.1 0.2 0.1 0.0 0.1 0.3 2.8 0.3 0.4 0.1 0.0 0.2 Lentimicrobium
saccharophilum NR149795 91.4
B36 Aminicenantes 0.0 6.8 0.2 0.2 0.0 0.8 0.3 0.0 0.3 0.1 0.0 0.0 0.0 0.1 Ca. Kuenenia
stuttgartiensis MH581445 84.2
B37 Bacteroidetes 0.0 0.1 0.6 0.0 2.1 0.4 0.2 0.0 0.0 0.0 0.0 0.1 0.1 0.0 Saccharicrinis
fermentans MG264242 89.7
B38 Pseudomonas 0.1 0.5 0.1 0.0 0.0 0.0 0.1 0.4 2.6 0.0 0.0 0.0 0.0 0.0 Pseudomonas veronii MG972914 99.3
B39 Bacteroidetes 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 2.3 0.2 0.1 0.0 0.2 0.2 Mariniphaga
anaerophila KP174641 92.8
B40 Chloroflexi 0.2 0.2 0.1 0.1 0.2 0.3 4.7 0.1 0.1 0.0 0.0 0.0 0.0 0.0 Litorilinea aerophila NR132330 89.3 B41 Saccharofermentans 0.2 0.3 0.8 0.6 0.4 2.5 0.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Ercella succinigenes HG003577 94.5
83
B42 Chloroflexi 0.0 0.2 0.1 0.0 0.0 0.0 2.3 0.0 0.3 0.0 0.0 0.0 0.0 0.0 Longilinea sp. AK5 MG734887 91.6
B43 Bacteria 0.0 1.9 0.0 0.0 0.0 4.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Pedinomonas
tuberculata KM462867 79.0
B44 Chloroflexi 2.4 0.0 0.0 0.0 0.0 0.0 0.0 0.7 0.0 0.0 0.0 0.0 0.0 0.0 Rubrobacter spartanus NR158052 84.4
a OTUs, operational taxonomic units. Cells with relative abundance values are shown in color in a heatmap-like fashion: green for archaeal sequences and red for bacterial sequences.
Libraries are labeled with the corresponding reactor name and dose (mM Fe) of magnetite (RM) or FeCl2 (RC).
b Lowest rank assigned using UCLUST against the RDP database.
c Closest cultivated sequences determined by BLAST search against the NCBI 16S rRNA sequence database.
d Sequence similarity.
e Ca., Candidatus.
Table 4-7 Relative abundance and taxonomic affiliation of major archaeal and bacterial OTUs (>2% relative abundance in at least one sample)a.
16S rRNA gene libraries 16S rRNA libraries
0 mM 8 mM 20 mM 0 mM 8 mM 20 mM
OTU no.
Classificationb R1 R2 R1 R2 R1 R2 R1 R2 R1 R2 R1 R2 Closest cultivated speciesc Accession
no.
Sim (%)d
A1 Methanothrix 89.1 91.1 2.7 5.2 1.0 1.8 91.6 90.5 8.4 4.8 4.3 2.1 Methanothrix LC413787 98.6
A2 Methanothrix 0.0 0.0 16.9 12.5 16.4 14.1 0.0 0.0 75.5 82.4 80.2 84.0 Methanosaeta concilii KM408635 98.6
A3 Methanobacteriacea
e 0.0 0.0 63.0 34.5 43.5 21.3 0.0 0.0 0.3 0.5 0.5 0.0
Methanobacterium
petrolearium NR113044 97.3
A4 Methanolinea 0.0 0.0 9.8 37.4 32.8 50.8 0.0 0.0 9.8 7.1 10.8 11.0 Methanolinea mesophila NR112799 96.2
A5 Methanothrix 2.2 3.2 2.4 3.5 0.4 1.1 4.1 6.3 5.0 4.2 1.4 1.6 Methanosaeta harundinacea CP003117 98.3
A6 Euryarchaeota 4.8 2.7 0.0 0.0 0.0 0.0 3.9 2.9 0.0 0.0 0.0 0.0 Methanobrevibacter KF697723 86.3
A7 Methanocella 0.0 0.0 1.4 2.0 3.1 3.4 0.0 0.0 0.9 0.6 1.9 0.7 Methanocella arvoryzae KF431947 97.9
A8 Pacearchaeota 3.6 2.4 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 Methanococcus AB518739 81.1
84 A9 Methanomassiliicoc
cus 0.0 0.1 0.6 1.9 1.2 5.5 0.0 0.0 0.0 0.0 0.1 0.4
Methanomassiliicoccus
luminyensis NR118098 93.8
B1 Paludibacter 0.2 0.6 1.5 2.1 2.9 3.5 2.6 8.3 49.0 45.0 35.5 21.2 Paludibacter MG763127 98.6
B2 Bacteroidetes 0.0 0.0 10.5 3.5 11.0 7.9 0.0 0.0 7.5 2.4 14.1 3.7 Solitalea canadensis KF528160 92.8
B3 Paludibacter 0.4 0.4 0.5 1.0 0.7 16.4 1.6 1.3 0.3 4.6 0.8 28.6 Paludibacter MG763127 93.5
B4 Desulfomicrobium 16.6 16.4 2.7 2.6 1.0 1.4 22.2 26.1 2.0 1.3 1.0 0.8 Desulfomicrobium norvegicum LS997916 98.3
B5 Bacteroidetes 0.1 1.9 6.9 10.6 4.8 8.5 0.3 2.8 5.0 6.6 7.5 7.6 Bacteroidetes bacterium AB623231 94.2
B6 Desulfobulbus 0.6 0.3 8.1 6.4 2.2 3.8 6.0 2.4 7.5 4.9 5.3 2.7 Desulfobulbus propionicus MF623798 98.6
B7 Saccharofermentans 12.9 9.4 2.3 5.1 1.5 2.0 0.2 0.0 0.0 0.0 0.1 0.1 Ruminococcaceae bacterium LK391549 97.6
B8 Smithella 0.1 0.1 0.4 0.5 0.6 0.8 3.6 2.7 4.4 4.8 4.6 5.2 Smithella propionica NR024989 96.2
B9 Sulfuricurvum 0.5 3.9 0.0 0.0 0.0 0.0 3.0 10.6 0.0 0.0 0.0 0.0 Sulfuricurvum KF494428 98.6
B10 Sulfurimonas 3.3 0.1 0.0 0.0 0.0 0.0 13.8 0.2 0.0 0.0 0.0 0.0 Sulfurimonas MN080872 93.8
B11 Bacteroidetes 6.0 4.6 1.2 2.2 1.4 1.8 1.6 1.2 0.1 0.4 0.2 0.4 Tangfeifania diversioriginum MK568413 89.7
B12 Chloroflexi 0.0 0.0 3.9 0.0 8.4 0.1 0.0 0.0 0.0 0.0 0.0 0.0 Ca.Roseilinea gracile KY937207 83.6
B13 Bacteroidetes 4.8 4.4 0.4 0.0 0.0 0.0 0.7 0.6 0.0 0.0 0.0 0.0 Alkaliflexus LK391566 89.5
B14 Bacteroidetes 0.0 0.0 2.6 0.8 2.4 0.5 0.0 0.0 2.3 0.4 3.1 0.4 Lentimicrobium
saccharophilum NR149795 93.5
B15 Anaerolineaceae 0.3 0.3 10.5 1.3 16.4 1.3 0.0 0.0 0.3 0.0 0.2 0.0 Levilinea saccharolytica KT183424 89.0
B16 Bacteroidetes 0.2 3.1 0.6 1.1 0.3 0.3 1.0 13.2 0.3 0.4 0.3 0.1 Bacteroidetes bacterium MK568430 96.2
B17 Saccharofermentans 0.2 0.3 0.6 1.2 1.4 3.1 0.0 0.0 0.3 1.0 0.6 1.4 Saccharofermentans acetigenes AB910750 95.9 B18 Candidatus
Cloacamonas 0.9 3.7 0.0 0.0 0.0 0.0 0.7 2.0 0.0 0.0 0.0 0.0 Ca. Cloacamonas
acidaminovorans CU466930 89.7
B19 Sphaerochaeta 0.0 0.0 0.5 0.6 0.7 1.6 0.0 0.0 0.5 2.6 3.6 4.2 Spirochaeta LN614382 82.9
B20 Lactobacillus 0.0 0.1 2.3 10.7 0.3 0.4 0.0 0.0 0.7 1.3 0.2 0.6 Lactobacillus curvatus MN493649 98.3
B21 Chloroflexi 11.5 10.7 1.1 0.8 1.6 0.5 0.4 0.3 0.0 0.1 0.1 0.0 Rubrobacter spartanus NR158052 84.2
85
B22 Clostridiales 0.2 0.0 1.2 3.9 1.7 1.9 0.0 0.0 0.2 0.6 0.3 0.5 Geosporobacter ferrireducens KY962942 88.7 B23 Anaerolineaceae 0.2 0.2 1.2 0.3 3.4 0.9 0.0 0.0 0.0 0.0 0.0 0.0 Leptolinea tardivitalis NR040971 90.4
B24 Chloroflexi 0.0 0.0 2.3 0.6 4.6 0.9 0.0 0.0 0.0 0.0 0.0 0.0 Longilinea MG734887 90.5
B25 Sulfurovum 1.6 0.0 0.0 0.0 0.0 0.0 6.5 0.0 0.0 0.0 0.0 0.0 Sulfurovum aggregans NR126188 96.6
B26 Treponema 0.3 4.7 5.4 1.9 1.1 2.5 0.1 0.9 0.6 0.2 0.9 0.9 Treponema zuelzerae NR104797 97.3
B27 Kosmotoga 6.4 5.2 0.1 0.2 0.2 0.1 0.3 0.2 0.0 0.0 0.0 0.0 Mesotoga infera LS974202 99.0
B28 Atopobium 1.3 4.6 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 Atopobium KF030213 97.6
B29 Bacteroidetes 0.3 0.2 0.0 0.0 0.0 0.0 3.9 2.3 0.0 0.0 0.0 0.0 Carboxylicivirga taeanensis NR133715 90.7
B30 Thermovirga 3.6 1.6 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 Thermovirga lienii NR074606 92.4
a OTUs, operational taxonomic units. Cells with relative abundance values are colored in a heatmap-like fashion: green for archaeal and red for bacterial sequences. Samples are labeled with the corresponding reactor name and dose of either magnetite or FeCl2.
b The lowest rank assigned by UCLUST against the RDP database.
c Closest cultivated sequences were determined by BLAST search against the NCBI 16S rRNA sequence database.
d Sequence similarity.
e Ca., Candidatus.
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Figure 4-10. Cluster dendrograms constructed based on the OTU distribution in the bacterial (A) and archaeal (B) 16S rRNA gene libraries and in the bacterial (C) and archaeal (D) 16S rRNA libraries obtained in RM and RC by high-throughput sequencing. Samples are labeled with the corresponding reactor names and iron doses (mM Fe; magnetite for RM and FeCl2 for RC). Bootstrap values higher than 70% (1000 replicates) are shown at the nodes.
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Figure 4-11. Cluster dendrograms constructed based on the OTU distribution in the bacterial (A) and archaeal (B) 16S rRNA gene libraries and in the bacterial (C) and archaeal (D) 16S rRNA libraries obtained in RM1 and RM2 by high-throughput sequencing. Samples are labeled with the corresponding reactor names and iron doses (mM Fe; magnetite for RM and FeCl2 for RC). Bootstrap values higher than 70% (1000 replicates) are shown at the nodes.