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Appl. Environ. Microbiol., Nov 1996, 4147-4154, Vol 62, No. 11
JR Stephen, AE McCaig, Z Smith, JI Prosser and TM Embley
We have conducted a preliminary phylogenetic survey of ammonia- oxidizing
beta-proteobacteria, using 16S rRNA gene libraries prepared by selective
PCR and DNA from acid and neutral soils and polluted and nonpolluted marine
sediments. Enrichment cultures were established from samples and analyzed
by PCR. Analysis of 111 partial sequences of c. 300 bases revealed that the
environmental sequences formed seven clusters, four of which are novel,
within the phylogenetic radiation defined by cultured autotrophic ammonia
oxidizers. Longer sequences from 13 cluster representatives support their
phylogenetic positions relative to cultured taxa. These data suggest that
known taxa may not be representative of the ammonia-oxidizing
beta-proteobacteria in our samples. Our data provide further evidence that
molecular and culture- based enrichment methods can select for different
community members. Most enrichments contained novel Nitrosomonas-like
sequences whereas novel Nitrosospira-like sequences were more common from
gene libraries of soils and marine sediments. This is the first evidence
for the occurrence of Nitrosospira-like strains in marine samples. Clear
differences between the sequences of soil and marine sediment libraries
were detected. Comparison of 16S rRNA sequences from polluted and
nonpolluted sediments provided no strong evidence that the community
composition was determined by the degree of pollution. Soil clone sequences
fell into four clusters, each containing sequences from acid and neutral
soils in varying proportions. Our data suggest that some related strains
may be present in both samples, but further work is needed to resolve
whether there is selection due to pH for particular sequence types.
Copyright © 1996, American Society for Microbiology
Molecular diversity of soil and marine 16S rRNA gene sequences related to beta-subgroup ammonia-oxidizing bacteria
Department of Zoology, Natural History Museum, London, United Kingdom.
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