Question

In E.coli, complete DNA replication requires
(a) 38 hours
(b) 20 minutes
(c) 38 minutes
(d) 3 minutes

Answer 1

Hint: Escherichia coli is called in short as E.coli, are bacteria commonly found in the intestine of animals and get released to the environment, also they have been extensively used in genetic engineering due to it's short generation time.

Complete answer:
In E.coli, complete DNA replication requires 20 minutes. The time required by the E.coli to double its number in a specific atmosphere is called the generation time. From organism to organism the generation time varies. The growth phase rate of an E.coli is shown as generation time where (G) is generation time, (t) is time per generation and n is the number of generations. Therefore the equation for calculating generation time is G=t/n.

Additional information:
- E Coli bacteria are known for their ability to transfer DNA by conjugation and transduction, which made them one of the most used organisms in the field of recombinant technology and genetic manipulation.
- E Coli is a facultative anaerobic bacteria of the genus Escherichia and has a rod- shaped structure. They are also coliform, gram- negative bacteria which is abundantly found in the gut of warm- blooded organisms.
- A majority of the strains of E.coli are non- virulent and do not harm humans, but some distinct variants of strains such as EPEC are known to cause gastrointestinal diseases and food spoilage.
So, the correct answer is ‘(b) 20 minutes’.

Note:
- Most of the harmless strains of E.coli form a symbiotic relationship with humans and constitute the normal microbiota of the intestine and helps humans to form vitamin K which helps in the clotting of blood and inhibit the growth of other harmful bacteria in the intestine.
- Diseases like cholecystitis, traveler’s diarrhea, neonatal meningitis, pneumonia, and bacteremia are caused by harmful E.coli strains. These strains get released into the environment through fecal matter and spread to a healthy person through contaminated water.
- The complete growth cycle of a bacteria is divided into four phases, which are lag phase, exponential growth phase, stationary phase, and death phase.