So the bacteria that I am currently working with is called C.perfringens and is a common soil bacteria that is also found in association with mammals as a commensal and sometimes as a pathogen. There are five serotypes (A-E), each associated with a set of different diseases and target organism which is either a mammal or poultry. C.perfringens is capable of producing up to 16 different toxins, although these are rarely expressed all at once. It is a saprophyte, so decays dead matter – hence most of its toxins are hydrolytic enzymes. The most common diseases caused by C.perfringens is food poisoning and necrotic enteritis (chickens).
It is also the fastest growing bacteria, with a doubling time of 10 minutes (E.coli’s doubling time is 20 minutes). It is an obligate anaerobe which makes it tricky to grow. I have to essentially streak it out onto TSC agar and then add a second layer of agar on top of that to create a highly anaerobic microenvironment. I also need to leave these microbes in an anaerobic chamber over night to completely remove any possible source of oxygen from their surroundings.
The final thing I want to mention is the TSC media I use to grow them. This media contains a source of sulphite which C.perfringens is able to reduce which is what causes the bacteria to show up black on these plates. They are one of the few Clostridia that can reduce sulphite, so this media acts as a differential media for C.perfringens.