Flow diagram of the different steps in the study of the struc-
ture and function of microbial communities. Genetic fingerprinting
by DGGE or TGGE of molecular markers is the heart of a strategy to
study the presence (DNA) and activity (rRNA or mRNA) of bacterial
populations in complex mixtures. Additional information about par-
ticular bacterial populations within the community can be obtained
by hybridisation analysis with taxon-specific probes. Furthermore,
individual bands can be excised from the gels and sequenced to
identify the community members. These techniques are also used to
monitor the success of isolation of bacteria in pure cultures, and to
screen clone libraries for redundancy.