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Journal of Bacteriology, March 1999, p. 1883-1891, Vol. 181, No. 6
Departamento de Microbiología y
Parasitología Sanitarias,
Received 3 September 1998/Accepted 13 January 1999
The Serratia marcescens N28b wbbL gene has
been shown to complement the rfb-50 mutation of
Escherichia coli K-12 derivatives, and a wbbL
mutant has been shown to be impaired in O4-antigen biosynthesis (X. Rubirés, F. Saigí, N. Piqué, N. Climent, S. Merino,
S. Albertí, J. M. Tomás, and M. Regué, J. Bacteriol. 179:7581-7586, 1997). We analyzed a recombinant cosmid
containing the wbbL gene by subcloning and determination of
O-antigen production phenotype in E. coli DH5
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Genetic Analysis of the Serratia
marcescens N28b O4 Antigen Gene Cluster
by sodium
dodecyl sulfate-polyacrylamide electrophoresis and Western blot
experiments with S. marcescens O4 antiserum. The results
obtained showed that a recombinant plasmid (pSUB6) containing about 10 kb of DNA insert was enough to induce O4-antigen biosynthesis. The same
results were obtained when an E. coli K-12 strain with a
deletion of the wb cluster was used, suggesting that the O4
wb cluster is located in pSUB6. No O4 antigen was produced
when plasmid pSUB6 was introduced in a wecA mutant E. coli strain, suggesting that O4-antigen production is
wecA dependent. Nucleotide sequence determination of the
whole insert in plasmid pSUB6 showed seven open reading frames (ORFs).
On the basis of protein similarity analysis of the ORF-encoded proteins and analysis of the S. marcescens N28b wbbA
insertion mutant and wzm-wzt deletion mutant, we suggest
that the O4 wb cluster codes for two dTDP-rhamnose
biosynthetic enzymes (RmlDC), a rhamnosyltransferase (WbbL), a
two-component ATP-binding-cassette-type export system (Wzm Wzt), and a
putative glycosyltransferase (WbbA). A sequence showing DNA homology to
insertion element IS4 was found downstream from the last
gene in the cluster (wbbA), suggesting that an
IS4-like element could have been involved in the
acquisition of the O4 wb cluster.
*
Corresponding author. Mailing address: Departamento de
Microbiología y Parasitología Sanitarias,
División de Ciéncias de la Salud, Facultad de Farmacia,
Universidad de Barcelona, 08028 Barcelona, Spain. Phone: 34-3-4024496. Fax: 34-3-4021886. E-mail: regue{at}farmacia.far.ub.es.
Journal of Bacteriology, March 1999, p. 1883-1891, Vol. 181, No. 6
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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