From MicrobeWiki, the student-edited microbiology resource
A Microbial Biorealm page on the genus Methanoculleus
Higher order taxa:
Archaea; Euryarchaeota; Methanococci; Methanomicrobiales; Methanomicrobiaceae
Methanoculleus submarinus sp. nov. Nankai-1
Description and Significance
Methane hydrates, an ice-like material that can trap methane in cages of latticed water molecules, form at temperatures up to about 15 or 16oC. This frozen methane is a huge untapped resource that possess much potential for energy use.
In a deep marine sediment isolated from the Nankai Trough off the eastern coast of Japan a methanogen was found. This methanogen, proposed as a new species Methanoculleus submarinus, is thought to be the supplier of the methane in the methane hydrates and further study of this microorganism could possibly help revolutionize the energy industry.
Methanoculleus submarinus has not yet been sequenced. The 16S rDNA sequences of Nankai-1 were 99.1% similar to Methanoculleus marisnigri JR1. Normally for a strain to be classified as a new species the 16S rDNA sequence needs to be under 98%, but Boone et al. (2003) argue that Nankai-1 should be a different species because the DNA reassociation value was low at only 49%.
Cell Structure and Metabolism
Strain Nankai-1 contains no outer membrane and is Gram negative. Its average cell diameter is 0.8 to 2 microns and is an irregularly shaped coccus. No motility as observed although flagella were detected. It can grow off H2 plus CO2 with methane (CH4) as the product. Formate can serve as a catabolic substrate. For cell carbon, acetate is the only organic nutrient required.
The optimum growing temperature for M. submarinus is 45oC, with a salinity of 0.1 to 0.4 M Na+ and a pH of 4.8 to 7.7. The estimated in situ temperature, however, is 15 to 16oC. M. submarinus can be found in deep marine sediments where methane hydrates occur.
Boon et al. 2003. Isolation of a Methanogen from Deep Marine Sediments That Contain Methane Hydrates, and Description of Methanoculleus submarinus sp. nov. Applied and Environmental Microbiology vol. 69 no.6: 3311-3316.