ANTIBIOTIC SUSCEPTIBILITY TESTING. Bacteria demonstrate two kinds of resistance to antibiotics, namely intrinsic resistance and acquired resistance. Intrinsic resistance means that the species was resistant to an antibiotic even before its introduction.
Radiation is naturally present in our environment, as it has been since before the birth of this planet. In addition, radiation can be produced artificially, as in medical x-rays and microwaves for cooking. Nonetheless, most people are not aware of all the natural and man-made sources of radiation in our environment.
Ozone is released naturally in the troposphere by plants and soil. These are such small amounts that they are not harmful to the health of humans, animals or the environment. Ozone that increases because of certain human activities does become a problem at ground level and this is what we think of as 'bad' ozone.