Environmental Engineering Reference
In-Depth Information
role in the decomposition of organic materials. Although understood primarily as soil
bacteria, they might be more abundant in freshwaters [10, 57].
Mycobacterium
(103
sequences)
was
the
most
frequently
observed
genus
in
Actinobacteria. It has been widely detected from contaminated soil or sediments [51].
Some species of
Mycobacterium
were the dominant PAH-degraders and played an
important role in degrading PAHs in contaminated mangrove sediments [7]. The following
abundant genera were
Aciditerrimonas
,
Conexibacter
,
Arthrobacter
, and
Ilumatobacter
. The
rest of genera were less than 5% of actinobacterial sequences.
Figure 7. Treemap of observed Actinobacteria taxons shown in their hierarchical order.
3.2.6. Minor Phyla
In addition to the five phyla described above, 26 minor phyla with 1601 sequences were
also observed based on the dataset. Of these minor phyla, only the phyla Chloroflexi (2.96%),
Planctomycetes (2.77%), Cyanobacteria (2.28%), and Verrucomicrobia (1.28%) represented
more than 1% of all the bacterial sequences, and accounted for over 73% of all minor phyla
sequences (Figure 1).
Some known genera were represented in these ‗minor phyla'. The most abundant of the
minor phyla, Chloroflexi, comprised 372 sequences. Members of the Chloroflexi are
generally found in intertidal sediment and moderately acidic wetland [11, 13, 34, 58].
Planctomycetes was the second most abundant of the minor phyla, to which 349 sequences
were assigned. A number of genera of the Planctomycetes, which were once thought to occur
primarily in aquatic environments, have been discovered in wetlands [12, 29]. As the third
most abundant minor phyla, Cyanobacteria occupy a broad range of habitats across all
latitudes wetlands. They are widespread in freshwater, marine and even in the most extreme
niches such as hot springs, and hypersaline bays [12, 59, 60]. Evidence suggests that
Verrucomicrobia are abundant within the environment, and important. The species of
Verrucomicrobia have been identified and isolated from fresh water and soil environments
[61].
