In your regular pile of compost is billions of microbes mostly bacteria who love the conditions of air, moisture and heat. They are the ones responsible for the rise and fall of temperature in your pile. Different microbes work accordingly to the temperature in the pile.
The Psychrophile microbes work best in low temperatures (10-21°C). They invade the pile and begin to burn or oxidize carbon releasing heat and nutrients in the form of amino acids as the temperature rises in the compost.
The Mesophile grow best (10-50°C). Most of the micro-organisms on earth belong to the group of mesophile, found in soil and water environments most of the diseases cause by bacteria and viruses that affect humans come from this group. They can spoil food and dead animal matter quickly. They love food scraps and important in breaking down organic matter. They are the real work horses of the compost heap.
The Thermophile grow and live in extremely hot environments (32-93°C), devoting their 3-5day life span to raising the temperature huge enough to destroy sneaky disease germs or weed seeds. This also generates humic acid which enables plants to assimilate the nutrients in the compost.