Bacteria Question

Question

Typically, some plates grow a bacterial lawn while others grows bacterial colonies. Why is there a difference in the growth pattern?

Answer 1

Hello Adrianna,

There are two possible answers to your question. The first would be empirical differences and the other would be biological differences.

Empirical differences: you may get a lawn of bacteria on a plate as opposed to defined punctate colonies because too much bacteria were plated. This is why researchers plate serial dilutions on bacteria plates if they are inoculating plates from a culture of unknown concentration.

Biological differences: alternatively you may be referring to the interesting biological differences of swarming type bacteria versus those that do not swarm. The most common example of a swarming bacteria Proteus mirabilis which causes urinary tract infections. This bacteria grows like any other bacteria except that at some point, bacteria will develop additional flagellum causing them to rapidly grow outward. This happens for bit until the cells stop swarming and then continue growing at their new destination. This process repeats continually, which eventually produces what appear to be lawns on an agar plate, or in some cases concentric rings on the entire plate.