Which method is used for detecting motility in bacteria?

Detecting motility in bacteria is effectively accomplished through the technique of stabbing soft-agar medium. This method involves inoculating a semi-solid agar tube by inserting a sterile needle or rod into the medium. As motile bacteria grow, they move away from the stab line, resulting in turbidity and diffusion throughout the agar, which indicates their mobility. Observing this spread of growth gives clear evidence of whether the organism is motile.

Streak plating, on the other hand, primarily isolates colonies rather than assessing individual cell movement. Inoculating broth culture may indicate general growth but does not provide information about motility specifically. Spread plating distributes cells evenly on a solid surface, facilitating colony counting but not motility assessment. Thus, stabbing soft-agar medium is the most suitable method for detecting bacterial motility.