Question

When performing a presumptive test with a water sample, you typically use a lactose broth with a durham tube and look for the indication of gas as a sign of fermentation.

If we use a phenol red lactose broth instead, do we still need to use the durham tube to see if fermentation happened and to determine if th bacteria are nonpotable?

Answer 1

A:- yes,you will still need of Durham tube when you use phenol red lactose broth. PhenolRed Broth is a general-purpose differential test medium typically used to differentiate gram negative enteric bacteria. It contains peptone, phenol red (a pH indicator), a Durham tube, and one carbohydrate.

There we use three kinds of phenol red broth:-

* Glucose

* One contains lactose

* One by sucrose

The objective of the exercise is to determine which organisms can utilize each sugar.Phenol red is a pH indicator which turns yellow below a pH of 6.8 and fuchsia above a pH of 7.4. If the organism is able to utilize the carbohydrate, an acid by-product is created, which turns the media yellow. If the organism is unable to utilize the carbohydrate but does use the peptone, the by-product is ammonia, which raises the pH of the media and turns it fuchsia.

When the organism is able to use the carbohydrate, a gas by-product may be produced. If it is, an air bubble will be trapped inside the Duhram tube. But If the organism is unable to utilize the carbohydrate, gas will not be produced, and no air bubble will be formed.

2. I think,it is nonpotable experiment because E.coli. bacteria is used here.

It's according to me it's nonpotable or potable,but you can find better than me,thankyou.