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Determine the correctness or otherwise of the following Assertion (a) and Reason (r):
Assertion (a) : Bacterial growth is called synchronous when majority of the cells are in same stage of the bacterial cell cycle.
Reason (r) : Synchronous culture can be obtained by growing bacteria in an enriched medium.
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- Both (a) and (r) are true and (r) is the correct reason for (a)
- Both (a) and (r) are true but (r) is not the correct reason for (a)
- (a) is true but (r) is false
- (a) is false but (r) is true
Correct Option: C
Assertion : A synchronous or synchronized culture is a microbiological culture or a cell culture that contains cells that are all in the same growth stage.
Reason : Synchronous cultures can be obtained in several ways :
• External conditions can be changed, so as to arrest growth of all cells in the culture, and then changed again to resume growth.
• Cell growth can also be arrested using chemical growth inhibitors.
• Cells in different growth stages have different physical properties. Cells in a culture can thus be physically separated based on their density or size, for instance. This can be achieved using centrifugation (for density) or filtration (for size).
• In the Helmstetter-Cummings technique, a bacterial culture is filtered through a membrane. Most bacteria pass through, but some remain bound to the membrane. Fresh medium is then applied to the membrane and the bound bacteria start to grow. Newborn bacteria that detach from the membrane are now all at the same stage of growth; they are collected in a flask that now harbors a synchronous culture.
