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Microbiota — The Omics Techniques
OMICS approaches stand for collective characterization and quantification of pools of biological molecules. A gram of feces contains 10 to 12th of microbes. Not all of them are the same, with some of them being present in higher quantities and other in lower quantities. If you visualize them as a ping-pong balls, 10 to 12th of the room is occupied by them balls, each of them of different colors, each color representing a microbial species. If you pick 10 balls, you cannot have an accurate representation of the composition, but if you pick one million, you can be close to it.
OMICS techniques in microbiome research are doing that. By taking a sample and analyzing, you can get a snapshot of the composition at a certain point. The most widely used technique to study the microbiome is 16s rRNA DNA profiling, and by using primers to amplify the 16s rRNA gene of all microbes, you can create a database of DNA sequences. From one fecal sample, you can generate 1000 to 1000000 of 16s DNA sequences. The microbe most abundant in the sample will be found back the most in terms of 16s DNA sequence reads, the microbes that are not very abundant will be not detected or will generate only few of those 16s DNA sequences. This can be used to find out what microbes are there, what microbes are well represented and what microbes are present in low numbers.
