Studying niche differentiation
An exciting new direction in molecular microbial ecology is
the analysis of enzyme encoding genes. Generally these
genes have more sequence variation than the relatively
conserved 16s rRNA encoding genes, and might, therefore,
be better molecular markers to discriminate between close-
ly related but ecologically different populations [41”].
Moreover, the use of functional genes makes it possible to
study the specific activities of bacterial populations.
Wawer et a/. [42”] were the first to use DGGE analysis of
[NiFe] hydrogenase gene fragments of Desu~owibrio
species, an important group of sulfate-reducing bacteria.
By comparative analysis of PCR products obtained from
genomic DNA and mRNA extracted from bioreactor sam-
ples incubated with hydrogen, the substrate for the [NiFe]
hydrogenase enzyme, the authors could demonstrate the
presence of different Desu~ofonihio populations, but only
the preferential expression of the [NiFe] hydrogenase
gene by one population. It was concluded that this popu-
lation might be better adapted to growth on hydrogen than
other Desulfoovibrio populations suggesting a niche differen-
tiation of closely related bacterial populations performing
different functions in the community. As more sequences
for other functional genes become available in the future,
we will soon be able to use PCR-DGGE/TGGE to relate
community structure and function.