Cytoplasmic Filament-Deficient Mutant of Treponema denticola Has Pleiotropic Defects

Authors

Jacques Izard, David Axelrod Institute for Public HealthFollow
William A. Samsonoff, David Axelrod Institute for Public Health
Ronald J. Limberger, David Axelrod Institute for Public Health

ORCID IDs

Izard https://orcid.org/0000-0002-5904-5436

Document Type

Article

Date of this Version

11-2-2000

Citation

Journal of Bacteriology (February 2001), pages 1,078–1,084

doi: 10.1128/JB.183.3.1078–1084.2001

Comments

Copyright 2001, American Society for Microbiology. Used by permission

Abstract

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.