Molds (or Mould as the British would spell it) growing in your home can be bad, but molds growing in your cheese can be good (who doesn't love a great blue cheese and there are plenty to choose from here in Wisconsin). And molds, such as the one responsible for penicillin, gave us the first antibiotics. But after years of misuse and overuse, antibiotic resistance is threatening us all (not so much threatening to send us back to the dark ages, but certainly back to pre-WWII)
Now a similar common variety of mold may be a means of reversing antibiotic resistance.
In the microscopic Serengeti, molds and bacteria are competitors in the circle of life, constantly competing and trying to out do each other. Molds and bacteria both emit toxins to try to out do each other and those toxins can be deadly or beneficial, depending on the circumstances. That is why the penicillium mold emits the toxins it does, to fight off bacteria competitors. As we are finding out, these chemicals are far more sophisticated that we imagined.