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Figure 1 Different communities of microorganisms predominate during the various composting phases. Starting decomposition carried by mesophilic microorganisms, which rapidly break down the soluble, readily degradable compounds. Temperature rises above 40°C, the mesophilic microorganisms become less competitive and are replaced by others that are thermophilic, or heat-loving. At temperatures of 55°C and above, many microorganisms that are human or plant pathogens are destroyed. High temperatures accelerate the breakdown of proteins, fats, and complex carbohydrates like cellulose and hemicelluloses, the major structural molecules in plants. Over 65°C kill many forms of microbes and limit the rate of decomposition, compost managers use aeration and mixing to keep the temperature below this point. Final phase of "curing" or maturation of the remaining organic matter.