Question

Unknown identification often begins with one or more streak plates. Why is this done? Which media ( from those used in the knowns project) will you use and why?

Answer 1

Streak plate technique is used for this because we want to grow the microbes present in our sample. Spread palting allows efficient separation of sample on plate so that we can get different types of colonies and isolate them. Hence the primary purpose of streaking is dilution of sample which would help in isolating different types of microbes present in the sample.

The nature of media depends on what you want to isolate. Different types of microbes require different source of energy. Hence you need different media for culturing different microbes. One of very common media is Luria broth which is used for growth of some fastidious microbes like enterobacters. Iron containing media are used for iron oxidizing micrones. So depending on the source of sample, type of sample, and which microbe you expect in your sample, media is chosen.