Microbial ecology of high-temperature compost and its usefulness as genetic resource

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Temperature reached over 90 degrees centigrade in the upper position of the compost of the high-temperature composting system. Viable cell numbers by surface plate method was about 1/100 to 1/1000 of those by microscopic observation method, suggesting that unculturable bacteria were important in the high-temperature composting process. Bacillus species dominated in the early stage of composting, accounting for 36% of the total cell numbers, but Melghirimyces thermohalophilus accounted for 63%, indicating that bacterial flora drastically changed in the process of the composting. Genes encoding thermophilic enzymes were directly cloned from DNA isolated from the compost and thermophilic bacteria producing bacterial cell wall-degrading enzymes were isolated from the compost, indicating that the high-temperature compost was quite useful as the genetic resource for isolating thermophilic enzymes and bacteria.