The first source I've included takes you to an Autoclave Time Temperature chart that shows you the temperature and pressure recommend to kill most bacteria. The standard practice is 121-degrees Celcius (250-degrees Fahrenheit). But it is not the heat alone that destroys the bacteria. Autoclaves also work under tremendous pressure (15psi or greater). It is the combination of heat and pressure that destroys the organisms.
The second source I've included also shows the exception to the rule. Certain bacteria, known as Thermophiles, actually THRIVE in intense heat and pressure. Some have even been found living in volcanic vents in the ocean depths.
So, while there is no exact answer, if you want to know what temperature is used as a standard for most sterilization devices, it would be 121 C (250 F).