DGGE of PCRamplified
16S rDNA fragments was
first used to profile community complexity of a microbial
mat and bacterial biofilms (Muyzer et al., 1993).
For this purpose bacterial genomicDNA was extracted
from natural samples, and segments of the 16S rRNA
genes were amplified in the polymerase chain reaction
(PCR; Saiki et al., 1988). This resulted in a mixture
of PCR products obtained from the different bacteria
present in the sample. The individual PCR products
were subsequently separated by DGGE. The resultwas
a pattern of bands, for which the number of bands corresponded
to the number of predominant members in
the microbial communities. To obtain more detailed
information about some of the community members,
DGGE profiles were blotted onto nylon membranes
and hybridised with a radioactivelylabelled
oligonucleotide
probe specific for sulfatereducing
bacteria
(Amann et al., 1992). In a subsequent study, Muyzer
and de Waal (1994) were able to identify community
members by sequencing of DNA eluted from excised
DGGE bands. Figure 1 gives a flow chart of the different
steps in this strategy.
Muyzer et al. (1995) used DGGE analysis of PCRamplified
rDNA fragments to provide information on
the genetic diversity of microbial communities found
around hydrothermal vents. Denaturing gradient gel
electrophoresis ofDNAfragments obtained after enzymatic
amplification of the 16S rDNA using genomic
DNA extracted from 2 different hydrothermal vent
samples and bacterial primers, showed only 1 band for