Genetic and Structural Analyses of Cytoplasmic Filaments of Wild-Type Treponema phagedenis and a Flagellar Filament-Deficient Mutant

Authors

Jacques Izard, David Axelrod Institute for Public HealthFollow
William A. Samsonoff, David Axelrod Institute for Public Health
Mary Beth Kinoshita, 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

8-1999

Citation

Journal of Bacteriology (November 1999): 6,739–6,746

Comments

Copyright 1999, American Society for Microbiology. Used by permission

Abstract

Unique cytoplasmic filaments are found in the treponeme genus of spirochete bacteria. Their function is unknown, but their location underneath the periplasmic flagellar filaments (PFF) suggests a role in motility and/or cell structure. To better understand these unique structures, the gene coding for the cytoplasmic filaments, cfpA, was identified in various treponemal species. Treponema phagedenis cfpA was 2,037 nucleotides long, and the encoded polypeptide showed 78 to 100% amino acid sequence identity with the partial sequence of CfpA from T. denticola, T. vincentii, and T. pallidum subsp. pertenue. Wild-type T. phagedenis and a PFF-deficient isolate were analyzed by electron microscopy to assess the structural relationship of the cytoplasmic filaments and the PFF. The number of cytoplasmic filaments per cell of T. phagedenis (mean, 5.7) was compared with the number of PFF at each end of the cell (mean, 4.7); the results suggest that there is no direct one-to-one correlation at the cell end. Moreover, a structural link between these structures could not be demonstrated. The cytoplasmic filaments were also analyzed by electron microscopy at different stages of cell growth; this analysis revealed that they are cleaved before or during septum formation and before the nascent formation of PFF. A PFF-deficient mutant of T. phagedenis possessed cytoplasmic filaments similar to those of the wild type, suggesting that intact PFF are not required for their assembly and regulation. The extensive conservation of CfpA among pathogenic spirochetes suggests an important function, and structural analysis suggests that it is unlikely that the cytoplasmic filaments and the flagellar apparatus are physically linked.