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

Ontogeny, Ontogeny: This is the study of history of an individual. Ontogen...

Ontogeny: This is the study of history of an individual. Ontogeny is also known as ontogenesis and morphogenesis. Ontogeny describes the origin or the development of an organism -

Define the mechanism of evolution, A few statements about the mechanism of ...

A few statements about the mechanism of evolution are made. Mark the correct statements.   (i)  Evolution happens at the individual level as well as population level. (ii

What is the meaning of term - plasticity, What is the meaning of term - Pla...

What is the meaning of term - Plasticity The notion of brain plasticity has been of interest to researchers and clinicians alike for decades. The outcome of injury is the resul

Renal function & cardiovascular - change related with ageing, Define Renal ...

Define Renal Function & cardiovascular - change related with ageing? Changes associated with the cardiovascular and renal function: The progressive accumulation of athermanous

Determine the importance of calcium in soils, Determine the importance of C...

Determine the importance of Calcium in soils Calcium in soils is usually abundant except in acid soils, which occur in humid areas due to excessive leaching. Deficiency of calc

Types of aortic stenosis-aortic stenosis-valve disease, Types of Aortic Ste...

Types of Aortic Stenosis:  Obstruction to left ventricular outflow is commonly at the valvar level. Less commonly it is at the sub valvar or supra valvar level. Sub valvar ob

Global alteration of brain functioning - sleep, Q. Global alteration of bra...

Q. Global alteration of brain functioning - Sleep? Sleep involves a global alteration of brain functioning, and occupies one third of our lives, The transition from waking to

Positive and negative regulation, Normal 0 false false fals...

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4 The lac operon is an

Poultry and duck diseases-duck plague, Duck plague Duck plague, caused ...

Duck plague Duck plague, caused by a member of Herpesviridae, has world wide distribution and occurs among domestic and wild ducks, geese, swans and waterfowls. Epidemiolo

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