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Applied and Environmental Microbiology, October 1998, p. 3860-3868, Vol. 64, No. 10
Instituto de Microbiologia Prof. Paulo de
Góes,
Received 31 October 1997/Accepted 28 July 1998
Paenibacillus azotofixans is a nitrogen-fixing
bacterium often found in soil and in the rhizospheres of different
grasses. In this study, two Brazilian clay soils were planted with
cross-hybrid maize (BR-201) and four stages of plant growth were
analyzed to characterize the P. azotofixans populations
present in the rhizoplanes, rhizospheres, and non-root-associated soils
(herein called nonrhizospheres). A total of 106 strains were isolated
and identified as P. azotofixans with an API 50CH kit, by
classical biochemical tests, and via the use of specific primers based
on the 16S rRNA gene in PCRs. To compare the isolated strains,
phenotypic characteristics were determined and three different probes
were used in hybridization experiments: two nif probes and
one probe comprising a 0.58-kb fragment cloned from the P. azotofixans C3L4 genome. These results were used to construct a
dendrogram, in which two main clusters could be observed. One cluster
contained exclusively strains from Várzea soil, and the other
contained the majority of strains from Cerrado soil. The 60 strains
from Várzea soil and the 46 strains from Cerrado soil were
further analyzed with REP and BOX primers, respectively. Based on the
patterns obtained, it was possible to identify 21 different groups
among strains from Várzea soil and 4 different groups among
strains from Cerrado soil. These different patterns were tested by
multivariate analysis of variance, and differences in the populations
of P. azotofixans during the four stages of plant growth
were demonstrated. Moreover, strains isolated from the rhizoplanes,
rhizospheres, and nonrhizospheres of maize planted in Cerrado and
Várzea soils were shown to be statistically different; the
diversity of P. azotofixans strains was affected by
the soil type.
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Comparison of Paenibacillus azotofixans Strains
Isolated from Rhizoplane, Rhizosphere, and Non-Root-Associated Soil
from Maize Planted in Two Different Brazilian Soils
*
Corresponding author. Mailing address:
Laboratório de Genética Microbiana, Depto. Microbiologia
Geral, Instituto de Microbiologia, Universidade Federal do Rio de
Janeiro, CCS, Bloco I, Ilha do Fundão, CEP 21941-590, Rio de
Janeiro, RJ, Brazil. Phone: 55-21-590 30 93. Fax: 55-21-259 99 57. E-mail: immgsel{at}microbio.ufrj.br.
Applied and Environmental Microbiology, October 1998, p. 3860-3868, Vol. 64, No. 10
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
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