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Applied and Environmental Microbiology, March 1999, p. 1207-1213, Vol. 65, No. 3
Department of Microbiology, Oregon State
University, Corvallis, Oregon 97331
Received 26 October 1998/Accepted 18 December 1998
Most techniques used to assay the growth of microbes in natural
communities provide no information on the relationship between microbial productivity and community structure. To identify actively growing bacteria, we adapted a technique from immunocytochemistry to
detect and selectively isolate DNA from bacteria incorporating bromodeoxyuridine (BrdU), a thymidine analog. In addition, we developed
an immunocytochemical protocol to visualize BrdU-labeled microbial
cells. Cultured bacteria and natural populations of aquatic
bacterioplankton were pulse-labeled with exogenously supplied BrdU.
Incorporation of BrdU into microbial DNA was demonstrated in DNA dot
blots probed with anti-BrdU monoclonal antibodies and either
peroxidase- or Texas red-conjugated secondary antibodies. BrdU-containing DNA was physically separated from unlabeled DNA by
using antibody-coated paramagnetic beads, and the identities of
bacteria contributing to both purified, BrdU-containing fractions and
unfractionated, starting-material DNAs were determined by length
heterogeneity PCR (LH-PCR) analysis. BrdU-containing DNA purified from
a mixture of DNAs from labeled and unlabeled cultures showed >90-fold
enrichment for the labeled bacterial taxon. The LH-PCR profile for
BrdU-containing DNA from a labeled, natural microbial community
differed from the profile for the community as a whole, demonstrating
that BrdU was incorporated by a taxonomic subset of the community.
Immunocytochemical detection of cells with BrdU-labeled DNA was
accomplished by in situ probing with anti-BrdU monoclonal antibodies
and Texas red-labeled secondary antibodies. Using this suite of
techniques, microbial cells incorporating BrdU into their newly
synthesized DNA can be quantified and the identities of these actively
growing cells can be compared to the composition of the microbial
community as a whole. Since not all strains tested could incorporate
BrdU, these methods may be most useful when used to gain an
understanding of the activities of specific species in the context of
their microbial community.
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Immunochemical Detection and Isolation of DNA from
Metabolically Active Bacteria
*
Corresponding author. Mailing address: Department of
Microbiology, 220 Nash Hall, Oregon State University, Corvallis, OR
97331. Phone: (541) 737-0717. Fax: (541) 737-0496. E-mail:
urbache{at}bcc.orst.edu.
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