Description of Gloeomargarita lithophora gen. nov., sp. nov., a thylakoid-bearing, basal-branching cyanobacterium with intracellular carbonates, and proposal for Gloeomargaritales ord. nov

Int J Syst Evol Microbiol. 2017 Mar;67(3):653-658. doi: 10.1099/ijsem.0.001679. Epub 2017 Apr 3.


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.

Keywords: Gloeomargarita; cyanobacteria, phylogeny.

MeSH terms

  • Bacterial Typing Techniques
  • Base Composition
  • Carbonates / chemistry
  • Chlorophyll / chemistry
  • Chlorophyll A
  • Cyanobacteria / classification*
  • Cyanobacteria / genetics
  • Cyanobacteria / isolation & purification
  • DNA, Bacterial / genetics
  • Lakes / microbiology*
  • Mexico
  • Phycocyanin / chemistry
  • Phylogeny*
  • RNA, Ribosomal, 16S / genetics
  • Sequence Analysis, DNA
  • Thylakoids


  • Carbonates
  • DNA, Bacterial
  • RNA, Ribosomal, 16S
  • Phycocyanin
  • Chlorophyll
  • Chlorophyll A