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Appl. Environ. Microbiol., 11 1997, 4223-4231, Vol 63, No. 11
G Wallner, B Fuchs, S Spring, W Beisker and R Amann
Not only classical cultivation-based methods but also the new molecular
approaches may result in incomplete and selective information on the
natural diversity of microbial communities. Flow sorting of microorganisms
from environmental samples allows the deliberate selection of cell
populations of interest from highly diverse systems for molecular analysis.
Several cellular parameters that can be measured by flow cytometry are
useful as sort criteria. Here, we report sorting of bacteria from activated
sludge, lake water, and lake sediment according to differences in light
scattering, DNA content, and/or affiliation to certain phylogenetic groups
as assessed by fluorescein-labeled, rRNA-targeted oligonucleotide probes.
Microscopy of the sorted cells showed that populations of originally low
abundance could be strongly enriched by flow sorting (up to 280-fold),
depending on the original abundance of the cells of interest and the type
of sample sorted. The purity of the cells of interest could be further
increased by repeated sorting, but this increase was limited by cell
aggregation in the case of activated-sludge samples. It was possible to
amplify almost full-length 16S ribosomal DNA (rDNA) fragments from sorted
microbial cells by PCR, even after fixation with paraformaldehyde and in
situ hybridization. Dot blot hybridization and sequencing demonstrated that
most of the amplified rDNA originated from those cells that had been
selected for by flow sorting. Comparative analysis of 16S rDNA sequences
revealed previously unknown species of magnetotactic or activated-sludge
bacteria.
Copyright © 1997, American Society for Microbiology
Flow sorting of microorganisms for molecular analysis
GSF-Forschungszentrum fur Umwelt und Gesundheit, Durchflusszytometrie, Neuherberg, Germany.
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