Question

Growth in which cells are physiologically identical and in same phase

Answer 1

Then after a short lag phase during which bacterium synthesizes the enzymes needed for lactose use, growth resumes with lactose as a carbon source. If this diphasic growth of E. coli is plotted in respect to bacterial density against time, two growth curves follow one after the other intervened by a short lag phase to produce a diauxic or diphasic growth curve (Fig. 19.3).

The enzyme needed for lactose use is β-galactosidase, which splits lactose into glucose and galactose, and the bacterium utilizes glucose for growth. Galactose can also be utilized, but only after it is converted to glucose. It has been demonstrated that E. coli growing in a medium containing both glucose and galactose produces a diauxic (diphasic) growth curve as in case of glucose and lactose.