Environmental Engineering Reference
In-Depth Information
Table 2. Estimates of current taxonomic coverage for Archaea and Bacteria
Distance
# Current OTUs
Rarefaction estimation
Coverage
a
(%)
Archaea
0.03
521
883
59
0.05
364
587
62
0.10
190
278
68
0.20
82
91
90
Bacteria
0.03
6383
15768
40
0.05
5042
9854
51
0.10
2937
4617
63
0.20
954
1118
85
a
Coverage = #OTUs/rarefaction estimate.
There was about 59% of the expected diversity revealed at the species level. The
estimates of current coverage of Euryarchaeota and Crenarchaeota were much greater than
that of Archaea. As the results of rarefaction analysis and diversity statistics, it was obvious
that the known bacterial and archaeal diversity in wetlands were incomplete below the
phylum level. Nevertheless, the global microbial diversity in wetlands revealed in this study
could serve as a framework for future studies of alpha and beta diversity. More specifically,
the collected sequence dataset could give a hand on detecting and quantifying specific groups
of either bacteria or archaea at the nucleotide level. Additionally, these studies will great
advance the ecology of individual microbia collected in the dataset.
Sufficient coverage and depth were provided to explore an individual sample or compare
multiple samples through multiplexing, with the development of second generation
sequencing technologies. Moreover, new sequences dataset could be added to the composite
datasets analyzed in this study to increase our knowledge on the diversity of this ecosystem.
The knowledge on the diversity may shine light on the understanding of the microbiomes of
wetlands, and define the significance of individual microbia. It is also suited for continuous
following of the succession variation of the diversity of wetlands.
However, the beta diversity was hardly to be determined because most of studies couldn't
contain large sequence datasets and detail information with same methodologies and
sequence submission criteria. A ‗core group' was defined after analyzing seven municipal
sludge digesters [66]. Although a distinct microbiome is possible be selected under a unique
environment, only a small number of ‗core OTUs' can be found among the large numbers of
OTUs identified. Systematic studies examining multiple wetlands designs with great depth of
coverage should help further define the ‗core microbiomes' in wetlands.
Now that the analysis of 16S rRNA gene sequences can provide insight into the
functional diversity of wetlands, the metabolic functions of organisms are getting more
concerned. For a well comprehension of the metabolic capacities of these organisms,
metagenomic studies techniques such as SIP and MAR-FISH should be used more frequently.
Cultivation-based studies are also needed to define the functions of uncharacterized species of
bacteria and archaea in wetlands.
