Question

How does Escherichia coli grow in a nutrient broth?

       I. turbid - finely dispersed growth throughout the broth

     II. sediment - granular substance at the bottom of the broth

Group of answer choices

Only I

Only II

Both I and II

Neither I or II

Answer 1

Escherichia coli is a gram-negative bacterium, non-spore-forming. It is generally motile because of the presence of peritrichous flagella.

Motility is the factor that decides the growth of the bacteria in the nutrient broth is turbid or sediment. The motile bacteria move in the broth creating uniform turbidity, whereas, few non-motile bacteria produce a surface membrane known as pellicle and keep floating at the surface of the broth. Other non-motile bacteria form sediments at the bottom of the broth after sinking to the bottom of the test tube.

Usually, Escherichia coli growth is turbid in a nutrient broth because they are motile, but few E.coli that are non-motile grow as sediments in the nutrient broth.

Hence, the option (c) is correct.