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Applied and Environmental Microbiology, September 1998, p. 3180-3187, Vol. 64, No. 9
Max-Planck-Institut für Terrestrische
Mikrobiologie,
Received 31 October 1997/Accepted 1 July 1998
Plant-pathogenic bacteria produce various extracellular
polysaccharides (EPSs) which may function as virulence factors in diseases caused by these bacteria. The EPS levan is synthesized by the
extracellular enzyme levansucrase in Pseudomonas syringae, Erwinia amylovora, and other bacterial species. The
lsc genes encoding levansucrase from P. syringae pv. glycinea PG4180 and P. syringae pv.
phaseolicola NCPPB 1321 were cloned, and their nucleotide sequences
were determined. Heterologous expression of the lsc gene in
Escherichia coli was found in four and two genomic library
clones of strains PG4180 and NCPPB 1321, respectively. A 3.0-kb
PstI fragment common to all six clones conferred levan synthesis on E. coli when further subcloned. Nucleotide
sequence analysis revealed a 1,248-bp open reading frame (ORF) derived from PG4180 and a 1,296-bp ORF derived from NCPPB 1321, which were both
designated lsc. Both ORFs showed high homology to the E. amylovora and Zymomonas mobilis lsc genes at
the nucleic acid and deduced amino acid sequence levels. Levansucrase
was not secreted into the supernatant but was located in the
periplasmic fraction of E. coli harboring the
lsc gene. Expression of lsc was found to be
dependent on the vector-based Plac promoter,
indicating that the native promoter of lsc was not
functional in E. coli. Insertion of an antibiotic
resistance cassette in the lsc gene abolished levan
synthesis in E. coli. A PCR screening with primers derived
from lsc of P. syringae pv. glycinea PG4180
allowed the detection of this gene in a number of related bacteria.
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Cloning, Nucleotide Sequence, and Expression in Escherichia
coli of Levansucrase Genes from the Plant Pathogens
Pseudomonas syringae pv. glycinea and P. syringae
pv. phaseolicola
*
Corresponding author. Mailing address:
Max-Planck-Institut für Terrestrische Mikrobiologie,
Karl-von-Frisch Strasse, 35043 Marburg, Germany. Phone: (49) 6421 178 600. Fax: (49) 6421 178 609. E-mail:
ullrichm{at}mailer.uni-marburg.de.
Applied and Environmental Microbiology, September 1998, p. 3180-3187, Vol. 64, No. 9
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
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