title: Description of Gloeomargarita lithophora gen. nov., sp. nov., a thylakoid-bearing, basal-branching cyanobacterium with intracellular carbonates, and proposal for Gloeomargaritales ord. nov.
abstract: A unicellular cyanobacterium, strain Alchichica-D10, was isolated from microbialites of the alkaline Lake Alchichica, Mexico. The cells were short rods (3.9±0.6 µm in length and 1.1±0.1 µm in width) forming biofilms of intense emerald green colour. They exhibited red autofluorescence under UV light excitation. UV-visible absorption spectra revealed that they contain chlorophyll a and phycocyanin, and electron microscopy showed the presence of thylakoids. The strain grew within a temperature range of 15-30 °C. Genomic DNA G+C content was 52.2 mol%. The most remarkable feature of this species was its granular cytoplasm, due to the presence of numerous intracellular spherical granules (16-26 per cell) with an average diameter of 270 nm. These granules, easily visible under scanning electron microscopy, were composed of amorphous carbonate containing Ca, Mg, Ba and Sr. A multi-gene phylogeny based on the analysis of 59 conserved protein markers supported robustly that this strain occupies a deep position in the cyanobacterial tree. Based on its phenotypic characters and phylogenetic position, strain Alchichica-D10 is considered to represent a new genus and novel species of cyanobacteria for which the name Gloeomargarita lithophora gen. nov., sp. nov. is proposed. The type strain is Alchichica-D10 (Culture Collection of Algae and Protozoa CCAP strain 1437/1; Collections de Cyanobactéries et Microalgues Vivantes of the Museum National d'Histoire Naturelle in Paris strain PMC 919.15). Furthermore, a new family, Gloeomargaritaceae, and a new order, Gloeoemargaritales, are proposed to accommodate this species under the International Code of Nomenclature for algae, fungi and plants.
authors.affiliation: Unité d'Ecologie, Systématique et Evolution, CNRS UMR 8079, Université Paris-Sud/Paris-Saclay, AgroParisTech, 91400 Orsay, France.
authors.forename: David
authors.initials: D
authors.lastname: Moreira
authors.affiliation: Facultad de Ciencias, Universidad Nacional Autónoma de México, CDMX, Mexico.
authors.forename: Rosaluz
authors.initials: R
authors.lastname: Tavera
authors.affiliation: Institut de Minéralogie, de Physique des Matériaux, et de Cosmochimie, Sorbonne Universités-UPMC Univ Paris 06, CNRS UMR 7590, MNHN, IRD UMR 206, Paris, France.
authors.forename: Karim
authors.initials: K
authors.lastname: Benzerara
authors.affiliation: Institut de Minéralogie, de Physique des Matériaux, et de Cosmochimie, Sorbonne Universités-UPMC Univ Paris 06, CNRS UMR 7590, MNHN, IRD UMR 206, Paris, France.
authors.forename: Fériel
authors.initials: F
authors.lastname: Skouri-Panet
authors.affiliation: Present address: School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA.|Facultad de Ciencias, Universidad Nacional Autónoma de México, CDMX, Mexico.|Unité d'Ecologie, Systématique et Evolution, CNRS UMR 8079, Université Paris-Sud/Paris-Saclay, AgroParisTech, 91400 Orsay, France.
authors.forename: Estelle
authors.initials: E
authors.lastname: Couradeau
authors.affiliation: Géobiosphère Actuelle et Primitive, Institut de Physique du Globe de Paris, CNRS UMR 7154, Université Paris Diderot, Sorbonne Paris Cité, Paris, France.
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Gérard
authors.affiliation: Nestlé Research Center, Minerals and Imaging Group, P.O Box 44, Ch-1000 Lausanne 26, VD, Switzerland.
authors.forename: Céline Loussert
authors.initials: CL
authors.lastname: Fonta
authors.affiliation: Facultad de Ciencias, Universidad Nacional Autónoma de México, CDMX, Mexico.
authors.forename: Eberto
authors.initials: E
authors.lastname: Novelo
authors.affiliation: Institut de Génétique et Microbiologie, CNRS UMR 8621, Université Paris-Sud/Paris-Saclay, 91405 Orsay, France.
authors.forename: Yvan
authors.initials: Y
authors.lastname: Zivanovic
authors.affiliation: Nestlé Research Center, Minerals and Imaging Group, P.O Box 44, Ch-1000 Lausanne 26, VD, Switzerland.
authors.forename: Purificación
authors.initials: P
authors.lastname: López-García
mesh_terms: D015373:Bacterial Typing Techniques; D001482:Base Composition; D002254:Carbonates / Q000737:chemistry; D002734:Chlorophyll / Q000737:chemistry; D000077194:Chlorophyll A; D000458:Cyanobacteria / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D004269:DNA, Bacterial / Q000235:genetics; D060106:Lakes / Q000382:microbiology*; D008800:Mexico; D010798:Phycocyanin / Q000737:chemistry; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D020524:Thylakoids
chemical_list: D002254:Carbonates; D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S; D010798:Phycocyanin; D002734:Chlorophyll; D000077194:Chlorophyll A
keywords: Gloeomargarita; cyanobacteria, phylogeny