Methanococci

By | July 26, 2021

Methanococci

It is the plural of methanococcus. Methanococcus is a genus of coccoid methanogens of the family Methanococcaceae. They are all mesophiles, except the thermophilic M. thermolithotrophicus and the hyperthermophilic M. jannaschii. The latter was discovered at the base of a “white smoker” chimney at 21°N on the East Pacific Rise and it was the first archaeal genome to be completely sequenced, revealing many novel and eukaryote-like elements.

Domain: Archaea

Kingdom: Euryarchaeota

Scientific name: Methanococcus

Order: Methanococcales

Rank: Genus

Higher classification: Methanococcaceae

Description and Significance:

  1. jannaschii was the first Archaeon to have its genome sequenced, which opened the doors for comparison between the genomes of the three domains. It was originally located from a sediment sample c
  2. ollected from the sea floor at the base of a “white smoker” chimney on the East Pacific Rise.

Methanocaldococcus jannaschii was formally in the genus Methanococcus, but due to its ability to grow in high temperatures it was re-classified. There were a few thermophilic species in Methanococcus that were reorganized, and this reorganization was supported by a low 16S rRNA sequence similarity between the thermophilics and mesophilics. The species left in Methanococcus are mesophilic and are related on the genus level by close DNA reassociation levels.

No difference is noted in the G + C content of thermophilics and mesophilics of Methanococcus. However, there is a difference in the proteins. The thermophilic proteins have higher residue volume, higher residue hydrophobicity, more charged amino acids, and fewer uncharged polar residues than the mesophilic proteins.

Genome Structure:

  1. jannaschii contains a main circular chromosome consisting of 1,664,970 bp, a large extra-chromosomal element with 58,407 bp, and a small extra-chromosomal element of 16,550 bp. There were similarities found in the genome with other domains, but there were also unique sequences.

The organism M. voltae was found to contain a system of gene transfer similar to general transduction except that the bacteriophage component (in terms of virus replication) is defective or absent. VTA (voltae transfer agent) is responsible for the transfer and its 4.4kb fragments of DNA are resistant to DNase. The majority of genes in M. jannaschii cannot be identified with Bacterial genomes or eukaryotic sequenced data. Of the similarities, Methanocaldococcus shared the anabolic genes with Bacteria (especially those involved in energy production and nitrogen fixation) and shared more of the cellular information processing and secretion systems with Eukaryotes.

 

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