Question

Explain and give a breif account of the life cycle of E.coli.

Answer 1

LIFE CYCLE OF ESCHERICHIA COLI:

• E coli includes both asexual and sexual reproductions in its life
  cycle.
• Its asexual reproduction is achieved by simple Binary fission The sexual reproduction of E. coli takes place by conjugation which occurs only between genetically differentiated strains.
• Some mating types of E. coli have a small extra-chromosomal DNA particle called sex factor or F, while other mating types may lack the sex factor.
• The bacterial strains with sex factors are called F+ or Hfr (male or donor) strains, while bacterial strains lacking the sex factor are called F or female acceptor strains.
• When a chance collision of F+ and F- bacteria takes place, both types of cells attach with each other and the walls between the two bacterial cells break open to form a small cytoplasmic bridge between the two.
• Through this cytoplasmic bridge the transfer of sex factor (DNA segment) of F cell to F or female bacterial cell, takes place and thus conjugation completes. The conjugating bacterial cells now separate and are called exconjugants.
• The receptor F- cell, thus, assumes a partial diploidy and is called "Merozygote".
• In the merozygote the sex factor remains incorporated with the circular DNA molecule of F-cells.
• The F- merozygote reproduces by cell division and ultimately regains monoploidy.

E.coli:

• Escherichia coli is also known as E. coli.
• It is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus Escherichia.
• It is commonly found in the lower intestine of warm-blooded organisms.