When working with microorganisms, it is important that the working environment stays as clean as possible. For example, a minuscule puff of mold spores can drift in air for an extended period of time and contaminate many subsequent experiments. Some of the spores can withstand even the temperature existing inside an autoclave and emerge from the sterilization process in dormant but viable forms. In general, the chance of contamination is proportional to the number of microorganisms in the environment when the same sets of aseptic procedures are taken. Of course, contamination means nothing but the waste of both the materials and the time spent. It can be an extremely maddening experience even for the calmest researcher. It is one's prerogative to be dirty or clean in one's own living quarters, but it is plainly irresponsible not to practice good aseptic techniques and keep the working environment clean, for not only himself but for everyone else as well. All the autoclaving will not help much in reducing the chances of contamination if the rest of the working environment is full of bugs as a result of improper attention to cleanliness. Although the presence of microorganisms cannot be totally eliminated in our lab economically, the numbers can certainly be reduced drastically by orders of magnitude. Uncleanliness simply does not pay in biochemical engineering!