Cultures used even in undergraduate labs are very concentrated, and thus even innocuous strains can cause disease.
Case in point: University of Chicago geneticist Dr. Malcolm Casadaban was working was a very weakened strain of Yersinia pestis, the bacteria that causes the plague. He passed away from an illness, probably septicemic plague, a form of the plague so rapidly fatal that it kills the person before other symptoms develop.
* Always wash your hands well with plenty of soap for 30 seconds when entering and leaving the lab.
* Disinfect your lab bench at the beginning and end of the lab with the provided disinfectant solution or a 2 percent solution of bleach in water.
* Treat every culture as if it was a pathogen.
* Microbiology labs use a Bunsen burner to create an updraft so bacteria will not settle into Petri dishes. Be careful around fire.
* Don't use alcohol-based hair products in microbiology labs with an open Bunsen burner. The residual alcohol catches on fire much more easily than you would expect.
* When you flame your inoculating loop (the device that looks like a magic wand topped with a piece of wire bent into a loop at the end) to sterilize it, don't dangle it over the flame like is shown in most textbooks. The fire travels up the loop and can burn your fingers.
* Hold the loop like Harry Potter holds his magic wand, base lower than the tip, then begin flaming the wire near where the wire enters the loop base. Slowly drag the loop down, like you're chasing contaminating bacteria up to the top of the loop with the flame. Flame the each section of the wire until it glows orange.
Media is the agar, or gelatin-like substance, in the bottom of Petri dishes and is used as food and substrate for bacteria. Different types of bacteria grow best on different agars.
Blood Agar (BAP) -- contains 5 to 10% mammalian blood, usually sheep or horse. Fastidious organisms like streptococcus grow well.
Chocolate Agar (CHOC) -- a blood agar where the blood cells were lysed by heating them to 56C. There is no actual chocolate in the agar. Used to isolate fastidious respiratory bacteria, like Haemophilus influenzae.
McConkey Agar (MAC) -- Inhibits growth of Gram-positive bacteria. Lactose-fermenting bacteria become pink colonies, while non-fermenting colonies are clear.
Nutrient Agar -- neither selective nor differential, a general-use agar that allows you to observe pigment formation.
All the admonitions about keeping yourself safe apply here, plus the following:
* Flame your loop early and often.
* Don't wear makeup, especially powder makeup, into the microbiology lab. It floats and will contaminate plates.
* Open bags of pipets from the bulb end, not the tip end. Remove pipets gingerly, without letting the bottom half of the pipet touch the inside of the bag.