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Applied and Environmental Microbiology, November 1999, p. 4855-4862, Vol. 65, No. 11
School of Biological Sciences,
Received 23 June 1999/Accepted 23 August 1999
The population of ammonia-oxidizing bacteria in a temperate
oligotrophic freshwater lake was analyzed by recovering 16S ribosomal DNA (rDNA) from lakewater and sediment samples taken throughout a
seasonal cycle. Nitrosospira and Nitrosomonas
16S rRNA genes were amplified in a nested PCR, and the identity of the
products was confirmed by oligonucleotide hybridization.
Nitrosospira DNA was readily identified in all samples, and
nitrosomonad DNA of the Nitrosomonas europaea-Nitrosomonas
eutropha lineage was also directly detected, but during the
summer months only. Phylogenetic delineation with partial (345 bp) 16S
rRNA gene sequences of clones obtained from sediments confirmed the
fidelity of the amplified nitrosomonad DNA and identified two sequence
clusters closely related to either N. europaea or N. eutropha that were equated with the littoral and profundal
sediment sites, respectively. Determination of 701-bp sequences for 16S
rDNA clones representing each cluster confirmed this delineation. A
PCR-restriction fragment length polymorphism (RFLP) system was
developed that enabled identification of clones containing N. europaea and N. eutropha 16S rDNA sequences, including subclasses therein. It proved possible to analyze 16S rDNA
amplified directly from sediment samples to determine the relative
abundance of each species compared with that of the other. N. europaea and N. eutropha are very closely related,
and direct evidence for their presence in lake systems is limited. The
correlation of each species with a distinct spatial location in
sediment is an unusual example of niche adaptation by two genotypically
similar bacteria. Their occurrence and relative distribution can now be routinely monitored in relation to environmental variation by the
application of PCR-RFLP analysis.
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Phylogenetic Differentiation of Two Closely Related
Nitrosomonas spp. That Inhabit Different Sediment
Environments in an Oligotrophic Freshwater Lake
*
Corresponding author. Mailing address: School of
Biological Sciences, Life Sciences Building, University of Liverpool,
Liverpool L69 7ZB, United Kingdom. Phone: 151 794 4413. Fax: 151 794 4401. E-mail: aj55m{at}liverpool.ac.uk.
Applied and Environmental Microbiology, November 1999, p. 4855-4862, Vol. 65, No. 11
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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