'The All-Species Living Tree' Project is a collaboration between various academic groups/institutes, such as ARB, SILVA rRNA database project, and LPSN, with the aim of assembling a database of 16S rRNA sequences of all validly published species of Bacteria and Archaea.
It is transcribed by RNA polymerase I as part of the 45S precursor that also contains 18S and 28S rRNA.
The model of Hm 50S determined in 2000 by Nenad Ban and colleagues in the laboratory of Thomas Steitz includes 2711 of the 2923 nucleotides of 23S rRNA, all 122 nucleotides of its 5S rRNA, and structure of 27 of its 31 proteins.
Eukaryotic 5S rRNA is synthesised by RNA polymerase III, whereas most other eukaroytic rRNAs are cleaved from a 45S precursor transcribed by RNA polymerase I.
The candidate division TM7, is a major lineage of Bacteria, the existence of which is known solely through environmental 16S rRNA sequences as to date no species has been grown in the lab, a requirement for taxonomy, making it a candidate phylum.
snoR41 was identified by computational screening the rice Oryza sativa genome and is predicted to act as a methylation guide for 18S and 25S ribosomal RNA (rRNA).
(p)ppGpp is thought to bind RNA polymerase and alter the transcriptional profile, decreasing the synthesis of translational machinery (such as rRNA and tRNA), and increasing the transcription of biosynthetic genes.