Bacteria will begin to die off at warmer temperatures, but hitting a temperature of 212°F, which is the boiling point of water, will destroy active bacteria within seconds.
Boiling Point (212°F): When bacteria encounter this temperature, the internal mechanisms of most bacteria will be quickly unraveled. Some hardy bacterial spores will survive this process, but it is still the best method for killing off most bacteria.
Pasteurization/Sanitization Range: It is worth noting that bacteria will die off at temperatures between 140°F and 149°F, but at these temperatures, the process will not happen instantly and will require minutes or even hours to be effective.