Question

Describe the process of qualitative water test for coliform contamination. If shown EMB plates, be able to determine if ...


Describe the process of qualitative water test for coliform contamination. If shown EMB plates, be able to determine if coliforms are present or not.

Answer

* Coliform bacteria are Bacteria and stains  Gram negative and they can be motile or non motile bacteria and non spore forming Bacteria.

*They are able to ferment the lactose with the production of acid and gas when incubated at 35–37°C.

*They are used indicator of sanitary quality of foods and water and can be found in aquatic environment and soil as well as  vegetation.

* They can be found in large numbers in the feces of warm blooded animals and not cause serious illness.

*They are very easy to culture and their presence is used to indicate other pathogenic organisms of fecal origin may be present. pathogens like disease causing bacteria and viruses or protozoa and multicellular parasites.

* Coliform procedures can be performed either in aerobic or anaerobic conditions. 

*Purity test has to be done to ensure the drinking is safe. The water can contain many types of contamination like chemical and  particulates, microbial contamination.

*The test for water purity is based on detections of specific indicator organism can be found in human faeces indicates contamination of water by sewage water and human faeces which can be harmful to humans. 

 

* ONPG test is also called as 0-nitrophenyl-β-D-Galactopyranosideused to detect the presence of the coliforms in the water.

*coliforms will produce the β-galactosidase by metabolising the lactose and enzymes act on ONPG and convert it into a yellow product.

*MUG test is also called as 4-methylumbelliferyl-β-D-glucuronide used to detect coliformes in water sample. 

*Enzyme β-galactosidase act on MUG and convert it to as fluorescent compound that emit bluish light with UV light.

*Example E.coli can be distinguished from most other coliforms by its ability to ferment lactose in the fecal coliform test.

*When cultured on an eosin methylene blue (EMB) plate they show metallic green colonies on a dark purple medium as a positive result.

*cultured on Tryptone Bile X-Glucuronide (TBX) to  show blue or green colonies as a positive result.

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