Exiguobacterium

Exiguobacterium is a genus of bacilli and a member of the low GC phyla of Firmicutes. Collins et al. first described the genus Exiguobacterium with the characterization of E. aurantiacum strain DSM6208T from an alkaline potato processing plant.[2] It has been found in areas covering a wide range of temperatures (-12^oC—55^oC) including glaciers in Greenland and hot springs in Yellowstone, and has been isolated from ancient permafrost in Siberia.[3] This ability to survive in varying temperature extremes makes them an important area of study. Some strains in addition to dynamic thermal adaption are also halotolerant (up to 13% added NaCl added to the medium), can grow within a wide range of pH values (5-11), tolerate high levels of UV radiation, and heavy metal stress (including arsenic).[4]

Exiguobacterium are globally diverse organisms that are found in a variety of environments including microbialites (Thrombolite[5] from Pavilion Lake, BC and Stromatolites[6] from Laguna Socompa, Argentina), ocean,[7] freshwater lakes,[8] Himalayan ice,[9] Himalayan soil,[10] hydrothermal vents,[11] brine shrimp [12] and in microbial biofilms [13]

Seven genomes from the genus have been completed as either complete (one circular chromosome, with plasmids) or in a draft format (containing multiple unassembled contigs). A new species of Exiguobacterium chiriqhucha has been found to have global distribution in cold lakes from Greenland, Pavilion Lake BC, and Laguna Negra, Argentina.[14] The 'Chiri qhucha' in Quechua means 'cold lake.' The study of Gutiérrez-Preciado et al. was confirmed by the completion of genomes two strains of Exiguobacterium chiriqhucha RW2 and GIC31.[15] Phospholipid fatty acid analysis (PLFA) of varying temperatures in Exiguobacterium chiriqhucha strain RW2 results in major rearrangements of cellular membrane function which may allow for its temperature, pH and salinity adaptation.[16]