Abstract
Several wastewater stabilization ponds (WSP) in Tunisia suffer periodically from the ‘red-water’ phenomenon due to blooming of purple sulfur bacteria, indicating that sulfur cycle is one of the main element cycles in these ponds. In this study, we investigated the microbial diversity of the El Menzeh WSP and focused in particular on the different functional groups of sulfur bacteria. For this purpose, we used denaturing gradient gel electrophoresis of PCR-amplified fragments of the 16S rRNA gene and of different functional genes involved in microbial sulfur metabolism (
dsr
B,
apr
A, and
puf
M). Analyses of the 16S rRNA revealed a relatively high microbial diversity where
Proteobacteria
,
Chlorobi
,
Bacteroidetes
, and
Cyanobacteria
constitute the major bacterial groups
.
The
dsr
B and
apr
A gene analysis revealed the presence of deltaproteobacterial sulfate-reducing bacteria (i.e.,
Desulfobacter
and
Desulfobulbus
), while the analysis of 16S rRNA,
apr
A, and
puf
M genes assigned the sulfur-oxidizing bacteria community to the photosynthetic representatives belonging to the
Chlorobi
(green sulfur bacteria) and the
Proteobacteria
(purple sulfur and non sulfur bacteria) phyla. These results point on the diversity of the metabolic processes within this wastewater plant and/or the availability of sulfate and diverse electron donors.