Choosing your inoculum and media

Now you must choose a medium. First, consider your source of water. Tap water usually contains a residual disinfectant such as chlorine, so aerate it for at least a day to get the chlorine out (so you don t kill your bacteria). The water may be hard (/.e, contain lots of calcium and magnesium) and may precipitate out needed metals when you make your media. That won t happen with distilled (Dl) water, but all the trace metals often needed by bacteria have been removed to extremely low concentration in Dl water, so it may not be optimal as well. You can always mix Dl and tap water to save on Dl water use. 

If you have a low concentration of bacteria, you may want to add cysteine (L-cysteine HCl) as this will chemically scavenge dissolved oxygen so that the solution can be anoxic. Cysteine reacts with oxygen to form a disulfide dimer (cystine), according to 

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