Methanocaldococcus jannaschii

It is a heat-adapted methane producer first described from material collected at a deep-sea hydrothermal vent.

Its energy economy centres on hydrogen and carbon dioxide rather than sunlight.

The original description reported motile cells with an irregular, approximately spherical form and a cell envelope that was vulnerable to osmotic disturbance.

These are observations of the described isolate, not a measured size range for every member of the species.

The reference strain is known as JAL-1, with culture-collection designations including DSM 2661 and ATCC 43067.

BacDive identifies that strain as anaerobic, meaning its documented growth physiology does not depend on oxygen.

Hydrogenotrophic methanogenesis uses hydrogen to reduce carbon dioxide, producing methane and water.

A simplified balanced reaction is 4 H₂ + CO₂ → CH₄ + 2 H₂O.

M. jannaschii is described as chemolithoautotrophic: inorganic chemistry supplies its energy, and inorganic carbon can supply the carbon used to build its cells.

In this system, methane production and cell growth are related processes, but methane is the metabolic product rather than the organism’s food.

Experiments found that lower hydrogen availability reduced both growth and methane production per cell.

In a coculture with the hydrogen-producing archaeon Thermococcus paralvinellae, M. jannaschii grew more slowly but produced more cells per mole of methane than in the comparison monocultures.

This is a useful reminder that growth rate, yield and methane output are different measurements: a cell population can change one without changing the others in the same way.

Microscopy and DNA-content work found multiple chromosome copies in growing M. jannaschii cells.

In the stationary-phase cells examined, chromosome counts ranged from one to five, with most cells carrying more than one copy.

The study also recorded asymmetric cell divisions and changes in the organisation of the nucleoid, the region occupied by chromosomal DNA.

It would therefore be misleading to picture every cell as holding one chromosome or to label five copies as an invariant species characteristic.

The original sample came from the base of a white-smoker chimney on the East Pacific Rise, at a reported depth of 2,600 metres.

The original investigators also documented laboratory growth at 85 °C.

Together, these observations establish a deep-sea origin and an ability to grow at high temperature, without defining a worldwide distribution.

The hydrogen-limitation experiments suggest that access to hydrogen, including hydrogen supplied by neighbouring microbes, can influence methane production in hot subseafloor communities.

They do not by themselves establish how much methane this species contributes to the ocean or atmosphere.

The 1996 genome report described a main genome of about 1.66 million base pairs plus two smaller extrachromosomal elements.

Its sequence comparison found many metabolic genes resembling bacterial counterparts, while much of the machinery for handling genetic information showed stronger similarity to eukaryotic counterparts.

That combination made the organism informative for comparing cellular systems; it did not make it a modern bacterium–eukaryote hybrid.

Older research calls the organism Methanococcus jannaschii, while the currently accepted combination is Methanocaldococcus jannaschii.

Recognising the older name helps readers connect the original physiological and genome papers to the same named species.

Is it a bacterium because early papers used that word?

No: the current taxonomic placement is in Archaea, even though terminology in historical descriptions can differ.

Does it need sunlight to make methane?

No: the documented energy pathway uses hydrogen and carbon dioxide.

Does the vent sample prove that it lives at every hydrothermal vent?

No: an isolation locality is evidence for that collection, not a complete distribution map.

The identity retained here is ncbi_taxonomy:2190, currently a species-rank NCBI record.

The original paper appeared in 1983, the basionym was validated in 1984, and LPSN dates the valid combination Methanocaldococcus jannaschii to Whitman 2002.

JAL-1, DSM 2661 and ATCC 43067 are linked type-strain designations, not three independently sampled species or three independent genome references.

The primary metabolic account supports hydrogenotrophic methanogenesis and chemolithoautotrophy, rather than a claim of photosynthetic growth.

BacDive’s pathway-presence table is explicitly computational, so a predicted pathway label there is not treated as experimental evidence for whole-cell physiology.

The hydrogen-transfer study compares monocultures with a Thermococcus paralvinellae coculture and separately measures growth rate, cell-specific methane production and yield.

Its repository abstract is sufficient for those qualitative comparisons, but the rendered hydrogen-concentration units are not carried into this article as a quantitative dataset.

Malandrin and colleagues’ abstract associates chromosome copy number and nucleoid organisation with culture growth phase.

A chromosome-copy count is a cellular state measurement, whereas the length of a reference sequence is a measurement of an assembled genetic representation.

The 1.66-million-base-pair figure belongs to the 1996 genome report and is not presented as a newly checked accession-specific assembly span.

The historical comparison of informational and metabolic genes is retained at the level stated in that report, without assigning this living species the status of a direct ancestor of other modern lineages.