Evidence for the prominence of well characterized mesophilic bacteria in thermophilic (50–70°C) composting environments

The prominent bacterial strains from both active (50–70°C) and presumably completed (ambient temperature) composts were isolated and identified using a carbon utilization technique with computerized database matching for bacterial identification. Prominent bacteria included Escherichia coli, Serratia, marcesens, Citrobacter freundii, Klebsiella pneumoniae, Enterococcus gallarium, Enterobacter cloacae, Pseudomonas aeuginosa, Pseudomonas pseudoalcaligenes, Pseudomonas alcaligenes, Actineobacter genospecies and Alcaligenes fecalis ss fecalis. When temperatures at sampling exceeded 60°C, the prominent bacteria found were assumed to be growing at or above this temperature, despite their classification as mesophils. The isolation of these strains from active compost strongly indicates that some mesophils have mechanisms for survival and perhaps replication at elevated temperatures, implicating a role in the composting process.