Temperature and Bacterial Survival
Temperature and Bacterial Survival is the study of how heat and cold affect whether germs live or die.
A bowl of soup on a hot stove kills the germs inside from the heat. Move that bowl into the fridge, and the germs slow down and go still but stay alive. A bowl left on the counter lets germs grow fast, like dots that spread across the surface. The warmth of the bowl decides what happens to the dots inside it.
Explaining temperature and bacterial survival by grade level
Germs are tiny living things all around us, too small to see. When you heat food up, the heat kills the germs. Cold slows germs down but does not kill them. You cook food to kill germs and chill it to slow them.
Projects that explore temperature and bacterial survival
Whether germs live or die depends on the species and the temperature they face. One experiment stores four types of bacteria at six temperatures ranging from 40°C down to -60°C. Each day, a set of vials returns to room temperature. After seven days, samples plate on blood agar and surviving colonies get counted. Comparing colony counts across temperatures reveals which species survive each extreme — and whether heat or cold proves more lethal.
Can bacteria survive boiling water or dry ice? Three species — E. coli, Streptococcus, and Bacillus — sit at five temperatures for two hours, ranging from -78°C (dry ice) up to 100°C (boiling). Then each sample transfers to agar Petri dishes and incubates for five days. Bacteria exposed to 60°C and 100°C show no growth at all. Those held at -78°C and 0°C, however, still grow normally — showing that high temperatures destroy bacteria completely while cold temperatures may not.