rRNA Cataloguing,rRNA Sequences,rRNA Molecules,Thermophillic Acid Tolerant,Procaryotic Phylogeny

rRNA Cataloguing

	rRNA Cataloguing - Over the past decade, comparative analysis of the 16 S rRNA sequences has been used to explore procaryotic phylogeny. The rRNA molecules are of choice because they are universally present in all organisms, have a constant function and appear to have changed in sequence, if at all very slowly. The 5 S rRNA has not been taken as an accurate indicator of phylogenetic relationship because of its smaller size.
The 16 S rRNA on the other hand, is sufficiently large and easy to handle with a high degree of precision while 23 S molecule is much larger and more difficult to characteriz. In recent years, therefore, the 16 S rRNA from a variety of organisms has been digested with ribonuclease T1 and the resulting nucleotides are resolved by two dimensional electrophoresis and sequenced. The availability of instruments that can sequence nucleic acids further helped in sequencing of 16 S rRNA from bacteria.
The comparison of catalogues represents genealogical relationship among organisms. This relationship can be quantified in term of an associate coefficient (SAB) Which is characteristic pf a pair of organisms SAB = 2NAB / NA+NB NA and NB = Total number of residues represented by oligomers of at least 6 nucleotides in catalogue A and B respectively,
NAB = Number of residues in sequences common to two catalogues. Upto Date, the rRNA sequences of more than 200 species of bacteria and eucaryotes have been characterized, Most of the bacteria form a coherent but very large group including the eubacteria. The methanogens, halophiles and thermoacidophiles (thermophillic acidtolerent) do not fall within the eubacteria. This type of rRNA sequencing has in fact allowed the characterization of arcbaebacteria.

Index >>Bacterial Classification>>rRNA Cataloguing

rRNA Cataloguing