Candidatus Glomeribacter gigasporarum

Candidatus "Glomeribacter gigasporarum" is a gram-negative β-proteobacteria.[1] The bacterium is rod-shaped, and has a obligate endosymbiotic relationship with the arbuscular-mycorrhizal fungi Gigaspora margarita.[2] Sequencing of the16S rRNA gene places Ca. "G. gigasporarum" within the Burkholderia genus.[1][2] Ca. "G. gigasporarum is unculturable as of yet, but can stay alive in enrichment for up to 4 weeks.[3] The candidate bacteria is considered "the smallest beta-proteobacterium" with a genome size of 1.4 Mb.[3] The chromosome is 750 kb long and a plasmid is 600 to 650 kb. The genome size was determined using gel-electrophoresis.[3]

Symbiotic relationship

The relationship between Ca. "G. gigasporarum" and the fungi Gigaspora margarita is obligate endosymbiotic. This occurs when either the symbiont or the host cannot live without each other. In this case the bacteria cannot live without the fungi. In certain studies, it has been found that over multiple generations of cloning certain spores of Gigaspora margarita contain no bacteria.[4] It was also found that these spores that lacked the bacteria had several different physiological changes in spore diameter, nuclear diameter, and wall thickness.[4] The fungi root system did not grow as abundant and changes in cell structure occurred in the fungi without bacteria.[4] The fungi were able to grow and complete their life cycle supporting that they can live without the symbiotic bacteria inside of them.[4] Since Ca. "G. gigasporarum" has only been found inside the fungi, it is the current idea that it cannot live by itself.

References
  1. Bianciotto, Valeria; Lumini, Erica; Bonfante, Paola; Vandamme, Peter (2003). "'Candidatus Glomeribacter gigasporarum' gen. nov., sp. nov., an endosymbiont of arbuscular mycorrhizal fungi". International Journal of Systematic and Evolutionary Microbiology. 53 (1): 121–124. doi:10.1099/ijs.0.02382-0. ISSN 1466-5026. PMID 12656162.
  2. Bianciotto, V.; Bandi, C.; Minerdi, D.; Sironi, M.; Tichy, H. V.; Bonfante, P. (1996-08-01). "An obligately endosymbiotic mycorrhizal fungus itself harbors obligately intracellular bacteria". Applied and Environmental Microbiology. 62 (8): 3005–3010. doi:10.1128/AEM.62.8.3005-3010.1996. ISSN 0099-2240. PMC 168087. PMID 8702293.
  3. Jargeat, P.; Cosseau, C.; Ola'h, B.; Jauneau, A.; Bonfante, P.; Batut, J.; Bécard, G. (October 2004). "Isolation, free-living capacities, and genome structure of "Candidatus Glomeribacter gigasporarum," the endocellular bacterium of the mycorrhizal fungus Gigaspora margarita". Journal of Bacteriology. 186 (20): 6876–6884. doi:10.1128/JB.186.20.6876-6884.2004. ISSN 0021-9193. PMC 522191. PMID 15466041.
  4. Lumini, Erica; Bianciotto, Valeria; Jargeat, Patricia; Novero, Mara; Salvioli, Alessandra; Faccio, Antonella; Bécard, Guillaume; Bonfante, Paola (2007). "Presymbiotic growth and sporal morphology are affected in the arbuscular mycorrhizal fungus Gigaspora margarita cured of its endobacteria". Cellular Microbiology. 9 (7): 1716–1729. doi:10.1111/j.1462-5822.2007.00907.x. ISSN 1462-5822.
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