Microorganisms sense and adapt to changes in their environment. When favored nutrients are exhausted, some bacteria may become motile to seek out nutrients, or they may produce enzymes to exploit alternative resources. One example of an extreme survival strategy employed by certain low G+C Gram-positive bacteria is the formation of endospores. This complex developmental process is often initiated in response to nutrient deprivation. It allows the bacterium to produce a dormant and highly resistant cell to preserve the cell’s genetic material in times of extreme stress.
Bacterial spores are one of the most resistant life forms known to date, being extremely tolerant against various stresses such as heat, chemicals, and harsh physical conditions. One of the signature properties of spores is heat resistance.
A biological indicator is made up of a carrier material, on which bacterial spores with a defined resistance to the sterilization process have been applied. RRS biological indicators are available in three different species of spores, Bacillus atrophaeus for ethylene oxide (EO) and dry heat applications, Geobacillus stearothermophilus for steam sterilization applications, and Bacillus pumilus for gama sterilization applications.
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