Gloeomargarita lithophora


Gloeomargarita lithophora, a cyanobacterium, is the proposed closest present day relative of all chloroplasts. The ancient relative of Gloeomargaritas was engulfed by a eukaryotic host in an endosymbiotic event around 1900-1400 million years ago. The origin of plastids by endosymbiosis signifies the beginning of photosynthesis in eukaryotes, and as such their evolutionary relationship to Gloeomargarita lithophora, as the sister group, is of high importance to the evolutionary history of endosymbiotic organelles and photosynthesis.

Description

G. lithophora was first isolated in 2007 from microbiolate samples taken from alkaline Lake Alchichica. These samples were maintained in a lab aquarium and G. lithophora was isolated from biofilm that occurred within the aquarium. G. lithophora are gram-negative, unicellular rods with oxygenic photoautotrophic metabolism and gliding motility. They contain chlorophyll a and phycocyanin and photosynthetic thylakoids located peripherally. Cells are 1.1 μm wide and 3.9 μm long on average. Growth occurred in both liquid and solid BG-11 growth media, as well as in alkaline water. Optimal growth temperature is 25 °C and optimal growth pH is 8–8.5.

Bioremediation

Some evidence suggests that Gloeomargarita lithophora could serve as a biological buffer to treat water contaminated with strontium, barium, or radioactive pollutants such as radium. This could be a useful application of bioremediation.