Explain the presumptive test - most probable number test, Biology

Assignment Help:

Explain the Presumptive Test - Most Probable Number Test?

The Presumptive test is used to detect and estimate coliform population of a water sample. This test is carried out by inoculating a series of lactose broth medium with three different sample volumes (10 ml, 1 ml and 0.1 ml). The series consists of 3 groups, each composed of 5 tubes and each group is inoculated with the designated volume of the water sample. The greater the number of tubes per group, the greater the sensitivity of the test. Lactose medium contains the lactose, bile salt and pH indicator.

Lactose and bile salts are selective for coliforms as lactose is used only by coliforms and not by other enteric bacteria while bile salts are depressent for enteric bacteria other than coliforms. A pH indicator such as bromocresol purple is added to the medium to detect acid fermentation from lactose. Production of acid changes the colour of the medium to yellow. Gas production during fermentation is detected by inverted Durham tube in lactose medium. Positive test for coliforms is indicated by the production of acid and gas from lactose fermentation after 24-48 hours of incubation. Number of tubes showing positive test is counted and the result is expressed as most probable number (MPN) of coliforms by matching the results

 


Related Discussions:- Explain the presumptive test - most probable number test

How to ensure food safety by haccp, Ensuring  Food  Safety It is now w...

Ensuring  Food  Safety It is now well-known that the end product inspection and  testing does not provide safety of food. It has inherent limitation of mapping the potential ha

Show the types of oesophagitis conditions, Q. Show the types of oesophagiti...

Q. Show the types of oesophagitis conditions? The two types of oesophagitis conditions: 1. Acute Oesophagitis - It is characterized by substantial pain on swallowing. It is

What is the resting membrane voltage of the neuron, What is the resting mem...

What is the resting membrane voltage of the neuron A complete motor neuron is removed from a frog and placed in normal physiological saline at 1 AM.  The neuron is healthy.  At

Explain the toxicity of vitamin d, Explain the Toxicity of Vitamin D? ...

Explain the Toxicity of Vitamin D? The adverse effects of high vitamin D intakes include hypercalciuria (excessive urinary calcium excretion) and hypercalcaemia (high concentr

Auxiliary food chains, Auxiliary Food Chains In addition to grazing an...

Auxiliary Food Chains In addition to grazing and detritus food chains there are other auxiliary food chains operated through parasites and scavengers. Some parasitic food chai

Determine the occurrence of vitamin A, Determine the Occurrence of vitamin ...

Determine the Occurrence of vitamin A In the vegetable kingdom, vitamin A  probably occurs in the form of its provitamins which belong to the group of carotenes. Carrots, spina

Potential disadvantages - digitalis glycosides, Arrhythmias especially in p...

Arrhythmias especially in presence of hypokalemia, lack of mortality benefit. However, their efficacy in reducing the symptoms of heart failure has been established. Digoxin should

Myocardial contractility, Inspiration decreases the pressure in the central...

Inspiration decreases the pressure in the central veins and thus increases the pressure gradient between the peripheral and central veins thus augmenting venous return. Skeletal mu

Bovine spongiform encephalopathy, Bovine spongiform encephalopathy The ...

Bovine spongiform encephalopathy The bovine transmissible spongiform encephalopathy (BSE), known as 'mad cow disease'-first noticed in Great Britain in 1986, is similar to scra

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd