What is the purpose of purification after concentration and

What is the purpose of purification after concentration and elution in sampling microbes in water? Also, please give some examples (purification techniques) for viruses and protozoa

Solution

We should purify the samples collected after concentration and during sampling microbes in water after concentration and elution, as to identify the microbes present in the particular sample.

Either we can go for standard method (which takes 4 to 5 days) or can go for MPN-qPCR method (which takes 24 hours) to identify the pathogen.

PCR and qPCR is widely used for accurate results. To prepare samples for PCR of qPCR we need utmost purity in the provided samples that is the reason why purification is must after concentration and elution.

In order to isolate viruses from the water samples, samples collected with treated with choloform to kill bacterial cells present. Then through centrifugation, the supernant alone will be collected by discarding the precipitate.
The collected supernatant will be then sterilized by membrane filtration.Here based on the requirement we can go for differential centrifugation, gradient centrifugation, differential precipitation, enzymatic degradation will be carried out to achieve purity in the sample.

Viruses like rotavirus, adenovirus, enterovirus, GI norovirus, GII norovirus, Hepatitis A virus, picomavirus, Falvivirus etc are commonly found in untreated waters.

Protozoa can be purified using chemical precipitation methods, by treating the samples with CaCl2 and Sodium bicarbonate. After some time, only the supernatant will be removed. Filtration and centrifugation are the best methods to separate out the protozoans from the water.

Protozoa like Cryptosporidium parvum, Balantidium coli, Giardia lamblia, Entamoeba, Trichomonas Intestinalis, Trichomonas vaginalis, Entamoeba histolytica etc are dound in untreated waters.