during the next lab period you will examine your agar slant

during the next lab period, you will examine your agar slant, agar plate, and broth culture. Assume you\'ll find growth on the slant and on the plate, but no growth in the broth. Did you expect this result? if yes or no, give a detailed explanation for this result.

Solution

The bacteria are of four kinds Aerobic, facultative aerobes, aero-tolerant anaerobes and strict anaerobes. Aerobic bacteria require oxygen, facultative can live both with oxygen or without oxygen, aero-tolerant are anaerobes that are not killed by oxygen and strict anaerobes are bacteria that can’t tolerate oxygen.

Most of the bacteria grown in laboratory classroom are aerobes that is they require oxygen to grow. The best place where bacteria can grow is on agar plate because air can readily diffuse into the bacterial colony. Diffusion of oxygen also depends on surface area that is exposed to oxygen. A large surface:volume ratio is required for the bacteria to grow.

On agar plates and agar slants the surface area:volume ratio is high therefore that bacteria can grow easily. Whereas, in agar broth the volume is high surface area exposed to air is low. Rapid shaking of broth is required to expose the broth to the surface.

if the total volume of liquid in the broth is more than 10-20% the aeration doesn’t take place adequately. Growing bacteria depletes the oxygen in the broth and becomes anoxic during less exposure to air. Thus, broth doesn’t show proper cultures compared to agar plate or slants.