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Applied and Environmental Microbiology, December 1998, p. 4650-4657, Vol. 64, No. 12
Molecular Ecology
Group,1
Microsensor
Group,2 and
Department of
Microbiology,3 Max Planck Institute for
Marine Microbiology, D-28359 Bremen, Germany
Received 8 May 1998/Accepted 16 September 1998
Recently, four Thiomicrospira strains were isolated
from a coastal mud flat of the German Wadden Sea (T. Brinkhoff and G. Muyzer, Appl. Environ. Microbiol. 63:3789-3796, 1997). Here we describe the use of a polyphasic approach to investigate the functional role of these closely related bacteria. Microsensor measurements showed
that there was oxygen penetration into the sediment to a depth of about
2.0 mm. The pH decreased from 8.15 in the overlaying water to a minimum
value of 7.3 at a depth of 1.2 mm. Further down in the sediment the pH
increased to about 7.8 and remained constant. Most-probable-number
(MPN) counts of chemolithoautotrophic sulfur-oxidizing bacteria
revealed nearly constant numbers along the vertical profile; the cell
concentration ranged from 0.93 × 105 to 9.3 × 105 cells per g of sediment. A specific PCR was used to
detect the presence of Thiomicrospira cells in the MPN
count preparations and to determine their 16S rRNA sequences. The
concentration of Thiomicrospira cells did not decrease with
depth. It was found that Thiomicrospira strains were not
dominant sulfur-oxidizing bacteria in this habitat. Denaturing gradient
gel electrophoresis (DGGE) of PCR-amplified 16S ribosomal DNA fragments
followed by hybridization analysis with a genus-specific
oligonucleotide probe revealed the diversity of
Thiomicrospira strains in the MPN cultures. Sequence
analysis of the highest MPN dilutions in which the genus Thiomicrospira was detected revealed that there were four
clusters of several closely related sequences. Only one of the 10 Thiomicrospira sequences retrieved was related to sequences
of known isolates from the same habitat. Slot blot hybridization of
rRNA isolated from different sediment layers showed that, in contrast
to the concentration of Thiomicrospira cells, the
concentration of Thiomicrospira-specific rRNA decreased
rapidly in the region below the oxic layer of the sediment. This study
revealed the enormous sequence diversity of closely related
microorganisms present in one habitat, which so far has been found only
by sequencing molecular isolates. In addition, it showed that most of
the Thiomicrospira populations in the sediment studied were quiescent.
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
A Polyphasic Approach To Study the Diversity and
Vertical Distribution of Sulfur-Oxidizing Thiomicrospira
Species in Coastal Sediments of the German Wadden Sea
*
Corresponding author. Present address: Netherlands
Institute for Sea Research. P.O. Box 59, NL-1790 AB Den Burg, Texel,
The Netherlands. Phone: 31-222-369-521. Fax: 31-222-319-674. E-mail: gmuyzer{at}nioz.nl.
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