Infection and Immunity, September 1998, p. 4100-4107, Vol. 66, No. 9
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Research Institute,
Received 20 April 1998/Returned for modification 22 May
1998/Accepted 2 June 1998
Shiga toxins 1 (Stx1) and 2 (Stx2) are encoded by toxin-converting
bacteriophages of Stx-producing Escherichia coli (STEC), and so far two Stx1- and one Stx2-converting phages have been isolated
from two STEC strains (A. D. O'Brien, J. W. Newlands, S. F. Miller, R. K. Holmes, H. W. Smith, and S. B. Formal, Science 226:694-696, 1984). In this study, we isolated two
Stx2-converting phages, designated Stx2
-I and Stx2
-II, from two
clinical strains of STEC associated with the outbreaks in Japan in 1996 and found that Stx2
-I resembled 933W, the previously reported
Stx2-converting phage, in its infective properties for E. coli K-12 strain C600 while Stx2
-II was distinct from them.
The sizes of the plaques of Stx2
-I and Stx2
-II in C600 were
different; the former was larger than the latter. The restriction maps
of Stx2
-I and Stx2
-II were not identical; rather, Stx2
-II DNA
was approximately 3 kb larger than Stx2
-I DNA. Furthermore,
Stx2
-I and Stx2
-II showed different phage immunity, with
Stx2
-I and 933W belonging to the same group. Infection of C600 by
Stx2
-I or 933W was affected by environmental osmolarity differently
from that by Stx2
-II. When C600 was grown under conditions of high
osmolarity, the infectivity of Stx2
-I and 933W was greatly decreased
compared with that of Stx2
-II. Examination of the plating efficiency
of the three phages for the defined mutations in C600 revealed that the
efficiency of Stx2
-I and 933W for the fadL mutant
decreased to less than 10
7 compared with that for C600
whereas the efficiency of Stx2
-II decreased to 0.1% of that for
C600. In contrast, while the plating efficiency of Stx2
-II for the
lamB mutant decreased to a low level (0.05% of that for
C600), the efficiencies of Stx2
-I and 933W were not changed.
This was confirmed by the phage neutralization experiments with
isolated outer membrane fractions from C600, fadL mutant,
or lamB mutant or the purified His6-tagged FadL
and LamB proteins. Based on the data, we concluded that FadL acts as
the receptor for Stx2
-I and Stx2
-II whereas LamB acts as the
receptor only for Stx2
-II.
*
Corresponding author. Mailing address: Research
Institute, International Medical Center of Japan, 1-21-1, Toyama,
Shinjuku-ku, Tokyo 162, Japan. Phone: 81-3-5273-6844. Fax:
81-3-3202-7364. E-mail: resedr{at}imcj.go.jp.
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