Dr. Bactoâs Combo is a product based on consortia of bacteria that fixes nitrogen, solubilizes srus and mobilizes potassium.The nitrogen-fixing bacteria in Dr. Bactoâs Combo fixes atmosric nitrogen and makes nitrogen available to the crops. srus-solubilizing bacteria solubilize insoluble srus and make srus available to crops. Potash mobilizing  bacteria mobilzes potash, increasing the plant's immune system.