title: Structural characterization of the cell division cycle in Strigomonas culicis, an endosymbiont-bearing trypanosomatid.
abstract: Strigomonas culicis (previously referred to as Blastocrithidia culicis) is a monoxenic trypanosomatid harboring a symbiotic bacterium, which maintains an obligatory relationship with the host protozoan. Investigations of the cell cycle in symbiont harboring trypanosomatids suggest that the bacterium divides in coordination with other host cell structures, particularly the nucleus. In this study we used light and electron microscopy followed by three-dimensional reconstruction to characterize the symbiont division during the cell cycle of S. culicis. We observed that during this process, the symbiotic bacterium presents different forms and is found at different positions in relationship to the host cell structures. At the G1/S phase of the protozoan cell cycle, the endosymbiont exhibits a constricted form that appears to elongate, resulting in the bacterium division, which occurs before kinetoplast and nucleus segregation. During cytokinesis, the symbionts are positioned close to each nucleus to ensure that each daughter cell will inherit a single copy of the bacterium. These observations indicated that the association of the bacterium with the protozoan nucleus coordinates the cell cycle in both organisms.
authors.affiliation: Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941-590, Brazil.
authors.forename: Felipe Lopes
authors.initials: FL
authors.lastname: Brum
authors.affiliation: Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941-590, Brazil.
authors.forename: Carolina Moura Costa
authors.initials: CM
authors.lastname: Catta-Preta
authors.affiliation: Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941-590, Brazil.
authors.forename: Wanderley
authors.initials: W
authors.lastname: de Souza
authors.affiliation: Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de São Paulo, São Paulo, SP, 04023-062, Brazil.
authors.forename: Sergio
authors.initials: S
authors.lastname: Schenkman
authors.affiliation: Laboratório Especial de Ciclo Celular, Instituto Butantan, São Paulo, SP, 05503-900, Brazil.
authors.forename: Maria Carolina
authors.initials: MC
authors.lastname: Elias
authors.affiliation: Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941-590, Brazil.
authors.forename: Maria Cristina Machado
authors.initials: MC
authors.lastname: Motta
mesh_terms: D001419:Bacteria; D002453:Cell Cycle / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D016054:DNA, Protozoan / Q000032:analysis / Q000737:chemistry; D008856:Microscopy, Fluorescence; D015388:Organelles / Q000737:chemistry / Q000382:microbiology; D013559:Symbiosis / Q000502:physiology*; D014351:Trypanosomatina / Q000737:chemistry / Q000166:cytology / Q000382:microbiology* / Q000502:physiology*
chemical_list: D016054:DNA, Protozoan