Penicillium (the source of the antibiotic penicillin) is a mold that secretes a toxin that kills bacteria and other organisms. Penicillium, however, is not harmed by this toxin. This is an example of:

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There are four nitrogenous bases that make up dna. the two pyramidines are thymine and cytosine. the two purines are adenine and guanine. these bases pair in a very specific way. adenine - thymineguanine - cytosine i remember it like this: a tall, good cat.