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Applied and Environmental Microbiology, August 1999, p. 3493-3501, Vol. 65, No. 8
Institute of Genetic Ecology, Tohoku
University, Katahira, Aoba-ku, Sendai 980-8577, Japan
Received 19 January 1999/Accepted 25 May 1999
From Bradyrhizobium japonicum highly reiterated
sequence-possessing (HRS) strains indigenous to Niigata and Tokachi in
Japan with high copy numbers of the repeated sequences RS
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
IS1631 Occurrence in Bradyrhizobium
japonicum Highly Reiterated Sequence-Possessing Strains with
High Copy Numbers of Repeated Sequences RS
and RS
and RS
(K. Minamisawa, T. Isawa, Y. Nakatsuka, and N. Ichikawa, Appl.
Environ. Microbiol. 64:1845-1851, 1998), several insertion sequence
(IS)-like elements were isolated by using the formation of DNA duplexes by denaturation and renaturation of total DNA, followed by treatment with S1 nuclease. Most of these sequences showed structural features of
bacterial IS elements, terminal inverted repeats, and homology with
known IS elements and transposase genes. HRS and non-HRS strains of
B. japonicum differed markedly in the profiles obtained after hybridization with all the elements tested. In particular, HRS
strains of B. japonicum contained many copies of
IS1631, whereas non-HRS strains completely lacked this
element. This association remained true even when many field isolates
of B. japonicum were examined. Consequently,
IS1631 occurrence was well correlated with B. japonicum HRS strains possessing high copy numbers of the
repeated sequence RS
or RS
. DNA sequence analysis indicated that
IS1631 is 2,712 bp long. In addition, IS1631
belongs to the IS21 family, as evidenced by its two open
reading frames, which encode putative proteins homologous to IstA and
IstB of IS21, and its terminal inverted repeat sequences
with multiple short repeats.
*
Corresponding author. Mailing address: Institute of
Genetic Ecology, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577, Japan. Phone: 81-22-217-5684. Fax: 81-22-263-9845. E-mail:
kiwamu{at}ige.tohoku.ac.jp.
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