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J. Bacteriol., 10 1995, 5959-5970, Vol 177, No. 20
EL Rosey, MJ Kennedy, DK Petrella, RG Ulrich and RJ Yancey Jr
Serpulina hyodysenteriae, the etiologic agent of swine dysentery, contains
complex periplasmic flagella which are composed of multiple class A and
class B polypeptides. To examine the role these proteins play in flagellar
synthesis, structure, and function and to develop strains which may provide
insight into the importance of motility in the etiology of this pathogen,
we constructed specific periplasmic flagellar mutations in S.
hyodysenteriae B204. The cloned flaA1 and flaB1 genes were disrupted by
replacement of internal fragments with chloramphenicol and/or kanamycin
gene cassettes. Following delivery of these suicide plasmids into S.
hyodysenteriae, homologous recombination and allelic exchange at the
targeted chromosomal flaA1 and flaB1 genes was verified by PCR, sequence,
and Southern analysis. The utility of a chloramphenicol resistance gene
cassette for targeted gene disruption was demonstrated and found more
amenable than kanamycin as a selective marker in S. hyodysenteriae.
Immunoblots of cell lysates of the flagellar mutants with antiserum raised
against purified FlaA or FlaB confirmed the absence of the corresponding
sheath or core protein. Both mutations selectively abolished expression of
the targeted gene without affecting synthesis of the other flagellar
polypeptide. flaA1 and flaB1 mutant strains exhibited altered motility in
vitro and were less efficient in movement through a liquid medium.
Paradoxically, isogenic strains containing specifically disrupted flaA1 or
flaB1 alleles were capable of assembling periplasmic flagella that were
morphologically normal as evidenced by electron microscopy. This is the
first report of specific inactivation of a motility-associated gene in
spirochetes.
Copyright © 1995, American Society for Microbiology
Inactivation of Serpulina hyodysenteriae flaA1 and flaB1 periplasmic flagellar genes by electroporation-mediated allelic exchange
Upjohn Company, Kalamazoo, Michigan 49001, USA.
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