title: The bacterium endosymbiont of Crithidia deanei undergoes coordinated division with the host cell nucleus.
abstract: In trypanosomatids, cell division involves morphological changes and requires coordinated replication and segregation of the nucleus, kinetoplast and flagellum. In endosymbiont-containing trypanosomatids, like Crithidia deanei, this process is more complex, as each daughter cell contains only a single symbiotic bacterium, indicating that the prokaryote must replicate synchronically with the host protozoan. In this study, we used light and electron microscopy combined with three-dimensional reconstruction approaches to observe the endosymbiont shape and division during C. deanei cell cycle. We found that the bacterium replicates before the basal body and kinetoplast segregations and that the nucleus is the last organelle to divide, before cytokinesis. In addition, the endosymbiont is usually found close to the host cell nucleus, presenting different shapes during the protozoan cell cycle. Considering that the endosymbiosis in trypanosomatids is a mutualistic relationship, which resembles organelle acquisition during evolution, these findings establish an excellent model for the understanding of mechanisms related with the establishment of organelles in eukaryotic cells.
authors.affiliation: Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil. motta@biof.ufrj.br
authors.forename: Maria Cristina Machado
authors.initials: MC
authors.lastname: Motta
authors.forename: Carolina Moura Costa
authors.initials: CM
authors.lastname: Catta-Preta
authors.forename: Sergio
authors.initials: S
authors.lastname: Schenkman
authors.forename: Allan Cezar
authors.initials: AC
authors.lastname: de Azevedo Martins
authors.forename: Kildare
authors.initials: K
authors.lastname: Miranda
authors.forename: Wanderley
authors.initials: W
authors.lastname: de Souza
authors.forename: Maria Carolina
authors.initials: MC
authors.lastname: Elias
mesh_terms: D001419:Bacteria / Q000166:cytology* / Q000235:genetics; D018407:Bacterial Physiological Phenomena; D002455:Cell Division; D002467:Cell Nucleus / Q000382:microbiology*; D003421:Crithidia / Q000166:cytology* / Q000382:microbiology* / Q000502:physiology; D004261:DNA Replication; D013559:Symbiosis