title: Intercellular transfer along the trichomes of the invasive terminal heterocyst forming cyanobacterium Cylindrospermopsis raciborskii CS-505.
abstract: Cylindrospermopsis raciborskii CS-505 is an invasive freshwater filamentous cyanobacterium that when grown diazotrophically may develop trichomes of up to 100 vegetative cells while differentiating only two end heterocysts, the sole sites for their N2-fixation process. We examined the diazotrophic growth and intercellular transfer mechanisms in C. raciborskii CS-505. Subjecting cultures to a combined-nitrogen-free medium to elicit N2 fixation, the trichome length remained unaffected while growth rates decreased. The structures and proteins for intercellular communication showed that while a continuous periplasmic space was apparent along the trichomes, the putative septal junction sepJ gene is divided into two open reading frames and lacks several transmembrane domains unlike the situation in Anabaena, differentiating a 5-fold higher frequency of heterocysts. FRAP analyses also showed that the dyes calcein and 5-CFDA were taken up by heterocysts and vegetative cells, and that the transfer from heterocysts and 'terminal' vegetative cells showed considerably higher transfer rates than that from vegetative cells located in the middle of the trichomes. The data suggest that C. raciborskii CS-505 compensates its low-frequency heterocyst phenotype by a highly efficient transfer of the fixed nitrogen towards cells in distal parts of the trichomes (growing rapidly) while cells in central parts suffers (slow growth).
authors.affiliation: Department of Molecular Genetics and Microbiology, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago 8331150, Chile Departament of Oceanography and Instituto Milenio de Oceanografía, Universidad de Concepción, Casilla 160-C, Concepción 4070386, Chile.
authors.forename: Álvaro M
authors.initials: ÁM
authors.lastname: Plominsky
authors.affiliation: Department of Molecular Genetics and Microbiology, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago 8331150, Chile.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Delherbe
authors.affiliation: Department of Molecular Genetics and Microbiology, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago 8331150, Chile.
authors.forename: Dinka
authors.initials: D
authors.lastname: Mandakovic
authors.affiliation: Department of Molecular Genetics and Microbiology, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago 8331150, Chile.
authors.forename: Brenda
authors.initials: B
authors.lastname: Riquelme
authors.affiliation: Department of Ecology, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago 8331150, Chile.
authors.forename: Karen
authors.initials: K
authors.lastname: González
authors.affiliation: Department of Ecology, Environment and Plant Sciences, Stockholm University, SE-10691 Stockholm, Sweden.
authors.forename: Birgitta
authors.initials: B
authors.lastname: Bergman
authors.affiliation: Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas and Universidad de Sevilla, E-41092 Sevilla, Spain.
authors.forename: Vicente
authors.initials: V
authors.lastname: Mariscal
authors.affiliation: Department of Molecular Genetics and Microbiology, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago 8331150, Chile mvasquez@bio.puc.cl.
authors.forename: Mónica
authors.initials: M
authors.lastname: Vásquez
mesh_terms: D017033:Anabaena / Q000235:genetics / Q000502:physiology; D001426:Bacterial Proteins / Q000378:metabolism; D019295:Computational Biology; D046891:Cylindrospermopsis / Q000235:genetics / Q000254:growth & development / Q000502:physiology* / Q000648:ultrastructure; D005452:Fluoresceins / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D046529:Microscopy, Electron, Transmission; D009586:Nitrogen Fixation; D009591:Nitrogenase / Q000378:metabolism; D016366:Open Reading Frames; D019897:Periplasm / Q000378:metabolism; D010641:Phenotype; D064201:Trichomes / Q000254:growth & development* / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D005452:Fluoresceins; C084577:5-carboxyfluorescein diacetate; D009591:Nitrogenase; C007740:fluorexon
keywords: Cylindrospermopsis raciborskii; diazotrophy; intercellular transfer