Question

Why are there different sizes of bacterial colonies?

Answer 1

Answer:

colony size reduce means somehow its growth rate was hampered. In your experiment you r use salt but salt has a negative effect on E.coli.It dis regulate the osmotic balance of this bacterial cell after tolerance concentration may be this is the main reason of smaller colony size.

Answer 2

The average colony size and total biomass on a plate are equivalent whether competition is local or global (assuming all resources are consumed). However, if the balance of uptake and diffusion causes interactions to be local, spatial location matters, and some colonies will grow much larger than others. Why do bacterial colonies reach a certain size and then stop growing? They deplete the accessible nutrients from the agar that is immediately around the colony. However, there are some species that spread out faster than the agar is depleted of nutrients. These species will overgrow the entire surface of the agar. Each distinct circular colony should represent an individual bacterial cell or group that has divided repeatedly. Being kept in one place, the resulting cells have accumulated to form a visible patch. Most bacterial colonies appear white, cream, or yellow in color, and fairly circular in shape. In general, as environmental conditions become less favorable, the pattern of growth in a colony becomes more complex. Two of the main factors that affect bacterial growth in a laboratory are media nutrient density and media hardness, the latter being a result of agar concentration.