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Applied and Environmental Microbiology, November 1999, p. 5042-5049, Vol. 65, No. 11
Max-Planck-Institut für terrestrische
Mikrobiologie, D-35043 Marburg, Germany,1 and
Institute of Terrestrial Ecology, Soil Biology, CH-8952
Schlieren, Switzerland2
Received 29 April 1999/Accepted 23 August 1999
Most-probable-number (liquid serial dilution culture) counts were
obtained for polysaccharolytic and saccharolytic fermenting bacteria in
the anoxic bulk soil of flooded microcosms containing rice plants. The
highest viable counts (up to 2.5 × 108 cells per g
[dry weight] of soil) were obtained by using xylan, pectin, or a
mixture of seven mono- and disaccharides as the growth substrate. The
total cell count for the soil, as determined by using
4',6-diamidino-2-phenylindole staining, was 4.8 × 108
cells per g (dry weight) of soil. The nine strains isolated from the
terminal positive tubes in counting experiments which yielded culturable populations that were equivalent to about 5% or more of the total microscopic count population belonged to the division Verrucomicrobia, the
Cytophaga-Flavobacterium-Bacteroides division, clostridial
cluster XIVa, clostridial cluster IX, Bacillus spp., and
the class Actinobacteria. Isolates originating from the
terminal positive tubes of liquid dilution series can be expected to be representatives of species whose populations in the soil are large. None of the isolates had 16S rRNA gene sequences identical to 16S rRNA
gene sequences of previously described species for which data are
available. Eight of the nine strains isolated fermented sugars to
acetate and propionate (and some also fermented sugars to succinate).
The closest relatives of these strains (except for the two strains of
actinobacteria) were as-yet-uncultivated bacteria detected in the same
soil sample by cloning PCR-amplified 16S rRNA genes (U. Hengstmann,
K.-J. Chin, P. H. Janssen, and W. Liesack, Appl. Environ.
Microbiol. 65:5050-5058, 1999). Twelve other isolates, which
originated from most-probable-number counting series indicating
that the culturable populations were smaller, were less closely related
to cloned 16S rRNA genes.
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Copyright © 1999, American Society for Microbiology. All rights reserved.
Characterization and Identification of Numerically
Abundant Culturable Bacteria from the Anoxic Bulk Soil of Rice
Paddy Microcosms

*
Corresponding author. Present address: Department of
Microbiology and Immunology, University of Melbourne, Parkville,
Victoria 3052, Australia. Phone: 61 (3) 9344 5706. Fax: 61 (3) 9347 1540. E-mail:
p.janssen{at}microbiology.unimelb.edu.au.
Present address: Department of Biological Sciences, Rutgers
University, Newark, NJ 07102.
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