Environmental Engineering Reference
In-Depth Information
3.2.4. Firmicutes
The fourth largest phylum was the Firmicutes, assigned into 973 sequences and 540
OTUs with a Simpson diversity index of 0.0041 (Figure 6). As saprophytic microbes, some
members of Firmicutes are known to produce endospores under stressful environmental
conditions such as in intertidal sediment [34], extremely alkaline (pH > 12) constructed
wetland [42].
About 45% of the Firmicutes sequences were classified to the class Clostridia, and nearly
36% were classified the class Bacilli. The Clostridia (sulfite-reducing bacteria) is an
anaerobic and highly polyphyletic bacterium, while Bacilli can be obligate aerobes or
facultative anaerobes. There was a long record of evidence to suggest that both of them were
the abundant taxa in sewage sludge [57].
Some species of them exhibits great ability to degrade hydrocarbons in crude oil
contaminated wetland ultisol [6]. Within the class Bacilli, two primary genera were
Bacillus
and
Pasteuria
, representing 107 and 98 sequences, respectively. While in Clostridia, Genus
Stricto
was the most abundant genera, with 56 sequences.
The class Negativicutes represented 178 sequences. The genus
Succinispira
represented
over 70% of sequences in Negativicutes.
Figure 6. Treemap of observed Firmicutes taxons shown in their hierarchical order.
The genus
Succinispira
,
the most abundant genus in Firmicutes, was capable of
decarboxylate succinate in anaerobic conditions. The class Erysipelotrichia represented only
three sequences.
3.2.5. Actinobacteria
As the fifth abundant phylum, Actinobacteria represented 783 sequences, clustered into
418 OTUs, with a Simpson diversity index of 0.0054. All of Acidobacteria sequences were
classified to the class Actinobacteria and over 66% of them belonged to order
Actinomycetales (Figure 7). Actinobacteria can be terrestrial or aquatic, playing an important
