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Journal of Bacteriology, August 2001, p. 4727-4736, Vol. 183, No. 16
Division of General Microbiology, Department of
Biosciences,1 and Institute of
Biotechnology,3 FIN-00014 University of
Helsinki, and National Public Health Institute (KTL), FIN-00300
Helsinki,2 Finland
Received 27 December 2000/Accepted 30 May 2001
A novel fimbrial type in Escherichia coli was
identified and characterized. The expression of the fimbria was
associated with the O18acK1H7 clonal group of E. coli,
which cause newborn meningitis and septicemia when grown at low
temperature; hence, it was named the Mat (meningitis associated and
temperature regulated) fimbria. The fimbriae were purified from a
fimA::cat sfaA::Gm
fliC::St derivative of the O18K1H7
isolate E. coli IHE 3034. The purified Mat fimbrillin
had an apparent molecular mass of 18 kDa and did not serologically
cross-react with the type 1 or S fimbria of the same strain. The
matB gene encoding the major fimbrillin was cloned from
the genomic DNA of the fimA::cat
sfaA::Gm fliC::St derivative
of IHE 3034. The predicted MatB sequence was of 195 amino acids,
contained a signal sequence of 22 residues, and did not show
significant homology to any of the previously characterized fimbrial
proteins. The DNA sequence of matB was 97.8% identical to a region from nucleotides 17882 to 18469 in the 6- to 8-min region
of the E. coli K-12 chromosome, reported to encode a
hypothetical protein. The 7-kb DNA fragment containing
matB of IHE 3034 was found by restriction mapping and
partial DNA sequencing to be highly similar to the corresponding region
in the K-12 chromosome. Trans complementation of the
matB::cat mutation in the IHE
3034 chromosome showed that matB in combination with
matA or matC restored surface expression
of the Mat fimbria. A total of 27 isolates representing K-12 strains
and the major pathogroups of E. coli were analyzed for
the presence of a matB homolog as well as for expression
of the Mat fimbria. A conserved matB homolog was found in 25 isolates; however, expression of the Mat fimbriae was detected only in the O18acK1H7 isolates. Expression of the Mat fimbria was
temperature regulated, with no or a very small amount of fimbriae or
intracellular MatB fimbrillin being detected in cells cultivated at
37oC. Reverse transcriptase PCR and complementation
assays with mat genes controlled by the inducible
trc promoter indicated that regulation of Mat
fimbria expression involved both transcriptional and
posttranscriptional events.
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.16.4727-4736.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
matB, a Common Fimbrillin Gene of
Escherichia coli, Expressed in a Genetically Conserved,
Virulent Clonal Group
*
Corresponding author. Mailing address: Division of
General Microbiology, Department of Biosciences, P.O. Box 56 (Viikinkaari 9), FIN-0014 University of Helsinki, Finland. Phone:
358-9-19159260. Fax: 358-9-19159262. E-mail:
timo.korhonen{at}helsinki.fi.
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