Spread Plate Method

∞ generated and posted on 2016.02.05 ∞

Means of microorganism isolation and enumeration involving culture application to solidified agar, agar which partially fills a Petri dish.

Contrast pour plate method and see also plate count. See also colony-forming unit.

Important is to employ agar possessing somewhat smooth surfaces, i.e., no "popped bubbles" present from earlier pouring. This is because cells will bunch within these depressions, resulting in excess bunching of colonies as well as a resulting under counting.

A second consideration is the volume of culture added, where excess volumes can result in pooling, which also will result in bunching, or worse (i.e., dripping). It is additionally important to strive to draw the liquid culture fully across the plates. This is rather than, again, having resulting colonies bunched up over only a fraction of the plate.

Lastly, the device employed for the spreading itself is affectionately described as a hockey stick. For illustration, see this Google image search on "spread plate".