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Journal of Bacteriology, February 2001, p. 1078-1084, Vol. 183, No. 3
Wadsworth Center, David Axelrod Institute for
Public Health, New York State Department of Health, Albany, New
York 12201-2002
Received 18 September 2000/Accepted 2 November 2000
In Treponema denticola, a ribbon-like structure of
cytoplasmic filaments spans the cytoplasm at all stages of the cell
division process. Insertional inactivation was used as a first step to determine the function of the cytoplasmic filaments. A suicide plasmid
was constructed that contained part of cfpA and a nonpolar erythromycin resistance cassette (ermF and
ermAM) inserted near the beginning of the gene. The plasmid
was electroporated into T. denticola, and double-crossover
recombinants which had the chromosomal copy of cfpA
insertionally inactivated were selected. Immunoblotting and electron
microscopy confirmed the lack of cytoplasmic filaments. The mutant was
further analyzed by dark-field microscopy to determine cell morphology
and by the binding of two fluorescent dyes to DNA to assess the
distribution of cellular nucleic acids. The cytoplasmic filament
protein-deficient mutant exhibited pleiotropic defects, including
highly condensed chromosomal DNA, compared to the homogeneous
distribution of the DNA throughout the cytoplasm in a wild-type cell.
Moreover, chains of cells are formed by the cytoplasmic
filament-deficient mutant, and those cells show reduced spreading in
agarose, which may be due to the abnormal cell length. The chains of
cells and the highly condensed chromosomal DNA suggest that the
cytoplasmic filaments may be involved in chromosome structure, segregation, or the cell division process in Treponema.
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.3.1078-1084.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Cytoplasmic Filament-Deficient Mutant of
Treponema denticola Has Pleiotropic Defects
*
Corresponding author. Mailing address: Wadsworth
Center, David Axelrod Institute for Public Health, New York State
Department of Health, P.O. Box 22002, Albany, NY 12201-2002. Phone:
(518) 474-4177. Fax: (518) 486-7971. E-mail:
Jacques.Izard{at}wadsworth.org.
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