Prometheoarchaeum syntrophicum
| Prometheoarchaeum syntrophicum | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Prometheoarchaeum syntrophicum | ||||||||||||
| Imachi et al. 2020 |
Prometheoarchaeum syntrophicum (strand MK-D1) is an archaeon (archaebacterium) from the Lokiarchaeota tribe , which enters into a symbiotic relationship between three partners with the Alphaproteobacterium Halodesulfovibrio from the order of the Desulfovibrionales and the Methanobacterium Methanogenium .
The symbiotic relationship between the Lokiarchaeoten Prometheoarchaeum syntrophicum and the Alphaproteobacterium Halodesulfovibrio is similar to the symbiotic relationship between the cytoplasm and the mitochondria in the nucleated cells of the nucleus ( eukaryotes ), to which humans also belong. The mitochondria are the power plants of the nuclear cells.
As things stand today, the next ancestors of the cell plasma of the nuclear cells are the Heimdallarchaeoten and the next ancestors of the mitochondria of the nuclear cells are the rickettsiae . How the nucleus of the nuclear cells came about is unclear.
Surname
The name Prometheoarchaeum alludes to the titan Prometheus ("the forerunner") who, according to Greek legend, brought man to earth from the abode of the Greek gods, Olympus . The term archaeum refers to the primordial bacteria, the archaebacteria , which today are called archaeonts, in English "original beings". The addition of the name syntrophicum means to feed together, i.e. together with the other cosymbiont .
Lokiarchaeota
The Lokiarchaeota tribe was only discovered in 2005 during an expedition to Loki's Castle , a group of five active hydrothermal vents (smokers) near the Mid-Atlantic Ridge at 73 ° latitude at a depth of 2352 m between Greenland and Norway.
In 2015, DNA fragments were discovered in this strain that indicated a close relationship with the nuclear cells ( eukaryotes ). The genes that both groups have in common include the genes for membrane transport , vesicle formation , vesicle transport , ubiquitin and cell skeleton .
The Lokiarchaeota belong to the super-tribe (Superphylum) of the Asgardarchaeota , which are named after the homeland of the Asen the Asgard in Norse mythology . The Asgardarchaeota include all tribes named after gods of Norse mythology, such as Thor, Odin, Loki, Heimdall and Hel.
Culture
In 2019, after 12 years of effort, a Japanese research group led by Masaru K. Nobu from the National Institute of Advanced Industrial Science and Technology in Tsukuba succeeded in permanently growing an archaeon growing in methane-containing sludge in the laboratory. Previously, the growth conditions had been examined for 6 years and then the archaeon together with its symbiotic partners gradually enriched until a culture of 13% Prometheoarchaeum, 85% Halodesulfovibrio and 2% Methanogenium was obtained.
Habitat
Prometheoarchaeum grows naturally in methane hydrate deposits at a depth of 2533 m on the bottom of the Nankai trough off the Kii peninsula in Japan.
Appearance
Prometheoarchaeum has a spherical body with a diameter of 300 to 750 nm. From this sprout long, sometimes branched processes with a diameter of 80 to 100 nm, which make direct contact with the symbiont Halodesulfovibrio .
Way of life
Prometheoarchaeum grows in a natural environment at a depth of 2500 m at an ambient temperature of 10 ° Celsius with exclusion of oxygen ( anaerobia ) in the sludge of deposits of methane hydrate . At these pressure conditions, methane is enclosed in crystal cages ( clathrates ) made of solidified water as gas hydrate (methane hydrate) and only escapes very slowly. The methane is not consumed by Prometheoarchaeum, but by the cosymbionts Halodesulfovibrio and Methanogenium. Prometheoarchaeum does not have to rely on a specific partner, but can cope not only with Halodesulfovibrio and Methanogenium, but also with Methanobacterium (symbiotic promiscuity ).
Prometheoarchaeum itself feeds on the hydrolysis of amino acids and peptides with the release of protons p + , which are also called Protia H + (singular: Protium). Protia are very mobile and active because they do not have an electron shell.
In the culture, Prometheoarchaeum grew best at 20 ° Celsius and a nutrient medium made from casein hydrolyzate and milk powder .
Multiplication
Prometheoarchaeum grows very slowly even under optimal conditions and divides once every 2 to 4 weeks, i.e. once every 20 days on average.
Enslavement of the cosymbiont
The Lokiarchaeon Promethoarchaeum combines under low-oxygen (anaerobic) conditions with an Alphaproteobacterium , such as Halodesulfovibrio, whereby the protons released by the Promethoarchaeum through hydrolysis of amino acids and peptides are used by the Alphaproteobacterium to synthesize high- energy compounds, which are then used again by the Lociarchaeon. The protium H + (= proton) from Promethoarchaeum and the hydrogen sulfide HS - from Halodesulfovibrio hydrogen sulfide H 2 S.
Similarly, under more oxygen-rich (aerobic) conditions, an Asgardarchaeon must have released protons to an Alphaproteobacterium, with the protium H + of the Asgardarchaeon and the hydrogen oxide HO - (= hydroxide) of the Alphaproteobacterium producing water H 2 O, similar to what is still happening today between Cell plasma and mitochondria, more precisely between the intermembrane space and the interior of the mitochondria, happens.
After Umschling, Umhüll, Versklav hypothesis (Engl. Entangle, Engulf, Enslave Hypothesis E3) took Asgardarchaeoten first (1) contact with the symbionts on, (2) wrapped around to secure it to the contact, (3) Sheathed Then, to increase the contact area, (4.) devour him to enslave him and (5.) finally gradually to incorporate his genes, i.e. to transport them from the symbiont into the cell plasma. In this way, the mitochondria , which serve as power stations for the cell, gradually emerged . Some proteins of the mitochondria are still stored on mitochondrial plasmids mtDNA and produced by mitochondrial ribosomes .
When the descendants of these archaeotes came to a nucleus , these genes were then transported into the nucleus. Archaeotes themselves do not have a nucleus.
As things stand today, the next ancestors of the cell plasma of the nuclear cells are the Heimdallarchaeoten and the next ancestors of the mitochondria of the nuclear cells are the rickettsiae .
The enslavement of the rickettsiae by Heimdallarchaeotes took place around 2.4 billion years ago in the Huronium , when the constant release of oxygen by cyanobacteria caused a great increase in oxygen .
Individual evidence
- ↑ Hiroyuki Imachi, Masaru K. Nobu et al .: Isolation of an archaeon at the prokaryote – eukaryote interface. (PDF) Nature, January 15, 2020, accessed on January 16, 2020 .
- ↑ Carl Zimmer: This Strange Microbe May Mark One of Life's Great Leaps. New York Times, January 15, 2020, accessed January 16, 2020 .