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Infection and Immunity, October 2001, p. 6012-6021, Vol. 69, No. 10
Bacterial Pathogenesis Research Group,
Department of Microbiology, Monash University, Victoria
3800,1 and Department of Microbiology
and Infectious Diseases, Royal Children's Hospital, Parkville,
Victoria 3052,2 Australia
Received 24 April 2001/Returned for modification 12 June
2001/Accepted 18 July 2001
Iron uptake systems which are critical for bacterial survival and
which may play important roles in bacterial virulence are often carried
on mobile elements, such as plasmids and pathogenicity islands (PAIs).
In the present study, we identified and characterized a ferric
dicitrate uptake system (Fec) in Shigella flexneri
serotype 2a that is encoded by a novel PAI termed the
Shigella resistance locus (SRL) PAI. The
fec genes are transcribed in S. flexneri, and complementation of a fec deletion in
Escherichia coli demonstrated that they are functional.
However, insertional inactivation of fecI, leading to a
loss in fec gene expression, did not impair the growth
of the parent strain of S. flexneri in iron-limited culture media, suggesting that S. flexneri carries
additional iron uptake systems capable of compensating for the loss of
Fec-mediated iron uptake. DNA sequence analysis showed that the
fec genes are linked to a cluster of multiple antibiotic
resistance determinants, designated the SRL, on the chromosome of
S. flexneri 2a. Both the SRL and fec loci
are carried on the 66,257-bp SRL PAI, which has integrated into the
serX tRNA gene and which carries at least 22 prophage-related open reading frames, including one for a P4-like integrase. This is the first example of a PAI that carries genes encoding antibiotic resistance and the first report of a ferric dicitrate uptake system in Shigella.
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.10.6012-6021.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Ferric Dicitrate Transport System (Fec) of Shigella
flexneri 2a YSH6000 Is Encoded on a Novel Pathogenicity
Island Carrying Multiple Antibiotic Resistance Genes
*
Corresponding author. Mailing address: Department of
Microbiology, Monash University, VIC 3800, Australia. Phone: 613 9905 4838. Fax: 613 9905 4811. E-mail:
harry.sakellaris{at}med.monash.edu.au.
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