16S rRNA: The diagnostic gene
16s rRNA is a non-coding RNA gene – so it reads or translates the information held in DNA to make proteins rather than making the proteins.
It is a very short piece of RNA – just 1,542 nucleotides in length, and it is what scientists call ‘highly conserved’. In other words this RNA translation tool has not changed much over millions to years. It is useful in finding out which genes belong to known organisms and which don’t in any given sample.
One issue with the microbial community is that to date, techniques have allowed only around 1% of the community to be understood, mostly because microbes from extreme environments are difficult to culture in the laboratory.
Fortunately there was an answer in the enzymes of extremophiles, the first being discovered in Yellowstone National Park in 1966 by Dr Thomas Brock. The microbe Thermus aquaticus yielded a heat-stable enzyme known as TAQ polymerase and this led to the development of the PCR – Polymerase Chain Reaction.
The PCR is like a superfast photocopier. What developers learned from Thermus aquaticus was a copying technique that could be amplified to make millions of copies of the 16s rRNA gene in just a few hours. Because 16s rRNA acts like one have of two pieces of Velcro, any genes left over from matching in a given sample can be attributed to genes from previously unknown organisms. The PCR provides enough material to do this.
We still know little about the microbial world, but yet microbes form the largest single biomass on Earth, even though individually they cannot be seen by the human eye.