Question

1A) What is the role of Citrase in bacteria?

A) energy source for glycolysis.

B) Citrate is brought into the bacterial cell

C) Helps the bacteria use the Krebs cycle by converting citrate into isocitrate.

D) Bacteria is able to use alternative sources of carbon by converting citrate backwards into pyruvate for fermentation.

E) Conversion of citrate into glutamate

1B)

For a phenol red test, a lactose phenol red broth was inoculated with a bacteria and after 24 hours it turned yellow. However, it was left for another 48 hours in the incubator and turned dark red. This is called___.

The bacteria has no more sugar to utilize and the pH will be __ (acidic or basic)?

What other energy source will the bacteria use now?

Answer 1

1A.) Answer is B.) Citrate is brought into bacterial cell. In absence of fermentable glucose and lactose, some bacteria arw capable of utilizing the citrate as the energy source for carbon. Here the Enzyme Citrate Permease enzyme helps the transport of citrate into bacterial cell. Thus helps in utlization.

1B.) Answer is Positive reaction. In the early phase if incubation the organisms utilze the carbohydrates source and produces acidic pH that converts the colour to yellow but as the incubation time increased the lack of carbohydrate source, the microorganism utlize the other source such as peptone in nutrient broth cause the end product as ammonia that makes the pH of medium alkaline(masking the acidic pH) resulting the dark red colour. The reaction should be absorbed within 48 hours. The extended incubation will result in masking of acidic pH after 48 hrs.

The bacteria has no more sugar to utlize the pH will be BASIC because of alternative soure of energy produce end product as ammonia that makes pH basic.

The other source of energy when sugars are over is Peptones present in the nutrient broth. By microbial enzymes the peptone is degraded to aminoacids and furthur to oxidative degradation. Makes available of kreb cycle as energy source.

Thankyou...