A method known as the "hot composting" method aims to create the right ratio of carbon rich and nitrogen rich materials in the pile in order to encourage thermophilic organisms to thrive in order to accelerate the process of making compost.
The following source 1 explains:
Need optimum temperature of 55-65 degrees Celsius. At temperatures over 65 degrees Celsius a white “mould” spreads through the compost, which is actually some kind of anaerobic thermophilic composting bacteria, often incorrectly referred to as”fire blight”. (It appears when the compost gets too hot – over 65 degrees Celsius and short of oxygen. It disappears when the temperature drops and aerobic composting bacteria take over).
What specific species is this organism?
I say prokaryote in the question title as I'm aware it may be a bacteria or archaea. Many sources incorrectly refer to archaea as bacteria.