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Appl. Environ. Microbiol., Jun 1995, 2257-2261, Vol 61, No. 6
T Hurek and B Reinhold-Hurek
The genus Azoarcus includes nitrogen-fixing, grass-associated strains as
well as denitrying toluene degraders. In order to identify and group
members of the genus Azoarcus, phylogenetic analysis based on partial
sequences of 16S rRNA genes (16S rDNAs) is proposed. 16S rRNA-targeted PCR
using specific primers to exclude amplification in the majority of other
members of the beta subclass of the class Proteobacteria was combined with
direct sequencing of the PCR products. Tree inference from comparisons of
446-bp rDNA fragments yielded similar results for the three known Azoarcus
spp. sequences and for analysis of the complete 16S rDNA sequence. These
three species formed a phylogenetically coherent group with representatives
of two other Azoarcus species which were subjected to 16S rRNA sequencing
in this study. This group was related to Rhodocyclus purpureus and Thauera
selenatis. New isolates and also sequences of so far uncultured bacteria
from roots of Kallar grass were assigned to the genus Azoarcus as well.
Also, strains degrading monoaromatic hydrocarbons anaerobically in the
presence of nitrate clustered within this genus, albeit not with
grass-associated isolates. All representative members of the five species
harboring rhizospheric bacteria were able to form N2O from nitrate and
showed anaerobic growth on malic acid with nitrate but not on toluene. In
order to visualize different Azoarcus spp. by whole-cell in situ
hybridizations, we generated 16S rRNA-targeted, fluorescent probes by in
vitro transcription directly from PCR products which spanned the variable
region V2. Hybridization was species specific for Azoarcus communis and
Azoarcus indigens.(ABSTRACT TRUNCATED AT 250 WORDS)
Copyright © 1995, American Society for Microbiology
Identification of grass-associated and toluene-degrading diazotrophs, Azoarcus spp., by analyses of partial 16S ribosomal DNA sequences
Abteilung Biogeochemie, Max-Planck-Institut fur Terrestrische Mikrobiologie, Marburg, Germany.
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