Gracilibacteria is a
bacterial candidate phylum formerly known as GN02, BD1-5, or SN-2. It is part of the
Candidate Phyla Radiation
The candidate phyla radiation (also referred to as CPR group) is a large evolutionary radiation of bacterial lineages whose members are mostly uncultivated and only known from metagenomics and single cell sequencing. They have been described as ...
and the Patescibacteria group.
The first representative of the Gracilibacteria phylum was reported in 1999 after being recovered from a deep-sea sediment sample. The representative 16S rRNA sequence was referred to as "BD1-5" (sample BD1, sequence 5) and while it was noted that it displayed low sequence identity to any known 16S rRNA gene, it was not proposed as a new phylum at this time. In 2006, representatives of Gracilibacteria were recovered from a hypersaline microbial mat from Guerrero Negro, Baja California Sur, Mexico and proposed as a new phylum "GN02". The name "Gracilibacteria" was proposed for the BD1-5/GN02 lineage in 2013, based on a substantial expansion of the genomic representation of this phylum.
The first Gracilibacteria genome was recovered from an acetate-amended aquifer (Rifle, CO, USA) using culture-independent, genome-resolved
metagenomic techniques in 2012. Genomic analyses suggest that members of the Gracilibacteria phylum have limited metabolisms and are likely
symbionts or
endosymbiont
An endosymbiont or endobiont is an organism that lives within the body or cells of another organism. Typically the two organisms are in a mutualism (biology), mutualistic relationship. Examples are nitrogen-fixing bacteria (called rhizobia), whi ...
s.
Members of Gracilibacteria use an alternative
genetic code
Genetic code is a set of rules used by living cell (biology), cells to Translation (biology), translate information encoded within genetic material (DNA or RNA sequences of nucleotide triplets or codons) into proteins. Translation is accomplished ...
in which UGA encodes the
glycine
Glycine (symbol Gly or G; ) is an amino acid that has a single hydrogen atom as its side chain. It is the simplest stable amino acid. Glycine is one of the proteinogenic amino acids. It is encoded by all the codons starting with GG (G ...
amino acid
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...
instead of a
stop codon
In molecular biology, a stop codon (or termination codon) is a codon (nucleotide triplet within messenger RNA) that signals the termination of the translation process of the current protein. Most codons in messenger RNA correspond to the additio ...
References
{{Taxonbar, from=Q26967716
Candidatus taxa
Bacteria phyla