Environmental Engineering Reference
In-Depth Information
Figure 3. Treemap of observed Proteobacteria taxons shown in their hierarchical order.
Classes in Proteobacteria showed various tendencies in different wetlands. The wide
distribution of Gammaproteobacteria and Deltaproteobacteria in marine sediment has been
documented, and most of them were involved in sulfur reduction under anaerobic conditions
[4]. In comparison, a high abundance of Alphaproteobacteria and Betaproteobacteria
appearance in freshwater sediment, and it is significantly correlated with pH and nutrients
[34]. Some genera of Betaproteobacteria were confirmed to inhabit extremely alkaline
wetlands filled with historic steel slag [42]. The Epsilonproteobacteria is relatively abundant
at oxic-anoxic interfaces such as intertidal wetland [43].
Deltaproteobacteria was the largest class in the phylum, with 1627 sequences (28.9% of
the proteobacteria).
Geobacter
of family Geobacteraceae, was the most abundant genus
(9.8%
of the Deltaproteobacteria) in Deltaproteobacteria. It was abundant in the rhizosphere, and has
been widely known as a kind of Fe (III)-reducing bacterium [44]. The followed abundant
genera were
Deltaproteobacteria
,
Desulfosarcina
,
Desulfopila
,
Desulfovibrio
,
Desulfonema
,
and
Desulfobacterium
, which represented greater than 1.0% of proteobacterial sequences. All
of them were sulfate-reducing bacteria, and their distributions were influenced by salinity and
plant nutrients [45]. They played important roles in the metabolism of nitrogen, phosphorus,
sulfur, and some organic compounds in wetland systems [18, 46].
Anaeromyxobacter
was also
the genus more than 1.0% proteobacterial sequences. As a kind of facultative bacteria, its
unique respiratory reduction of nitrate and nitrite to ammonia were not linked to its ability to
reduce nitrous oxide to nitrogen gas [47].
For the class Gammaproteobacteria, 1456 sequences were identified. It was the second
largest class in Proteobacteria. Approximate 12.6% of gammaproteobacterial sequences (184
sequences) were assigned to the genus
Rhodanobacter
of family Xanthomonadaceae. This
genus might be engaged in acidic denitrification in wetland soils [3]. The following abundant
genera were
Thioprofundum
and
Methylobacter
, accounting for 8.9% (129 sequences) and
8.0% (108 sequences) of gammaproteobacterial sequences, respectively.
Thioprofundum
was
recently concerned as a mesophilic, facultatively anaerobic, sulfur-oxidizing bacterial strain
