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Infect. Immun., Aug 1997, 3112-3117, Vol 65, No. 8
AE Fiore, JM Michalski, RG Russell, CL Sears and JB Kaper
Phospholipases are associated with virulence in bacterial diseases. Vibrio
cholerae produces a phospholipase (lecithinase), with enzyme production
visualized as a zone of clearing around colonies plated on egg yolk agar.
The role of phospholipase in gut colonization or disease pathogenesis is
unknown. We used the egg yolk agar assay to clone and characterize a gene
encoding a phospholipase from V. cholerae El Tor strain E7946. Sequence
analysis revealed a 1,254-bp open reading frame (lec) encoding a
418-amino-acid protein with a predicted molecular weight of 47,600. The
predicted sequence exhibits DNA homology to other Vibrionaceae
phospholipases. A potential signal sequence exists in the predicted amino
acid sequence, as does a lipid binding motif found in prokaryotic and
eukaryotic phospholipases and lipases. Polyacrylamide gel electrophoresis
combined with an egg yolk agarose overlay demonstrated phospholipase
activity migrating at a relative molecular weight of 45,000 in preparations
of V. cholerae and the Escherichia coli clone. Restriction mapping and
Southern blot analysis revealed that lec, hlyA (hemolysin), and hlyC
(lipase) are adjacent on the V. cholerae chromosome, and chromosomal
digests of several El Tor, classical, and O139 (Bengal) strains
demonstrated conservation of this gene arrangement. An in-frame internal
deletion of the lec gene was constructed and recombined into the chromosome
of attenuated V. cholerae El Tor strain CVD 110. The resulting mutant
lacked lecithinase activity on egg yolk agar but had undiminished
reactivity in rabbit ligated ileal loop assays.
Copyright © 1997, American Society for Microbiology
Cloning, characterization, and chromosomal mapping of a phospholipase (lecithinase) produced by Vibrio cholerae
Center for Vaccine Development, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
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