What are the advantages and disadvantages of high population density to a population

The microbes can be enumerated by streaking, pour plating, or spreading.

Streak plate gives isolated colonies, in which the counting of the microbial colony forming units is easier. 

Pour plating is mostly used for food items. The bacterial load in the foods is counted by this techniques, as chances of error are less in the pour plates technique, but one has to be careful, to not to add hot media on the inoculum, otherwise it will kill the microbes.

Spreading is also used in some cases, one has to be cautious to evenly spread the culture, as a small amount of culture is used in this technique.