The bacteria involved in an outdoor single phase composting using sawdust and wheat bran as substrates for cultivation of Lentinus tuber-regium (Fr). Composting was carried out for 15 days. The highestcore and peripheral temperatures were 66 and 45oC, respectively, while the lowest temperature was 36oC. The highest number of bacteria in the core and peripheral compost were 5.81x106 and 6.51x106 cfu/ml,respectively. Bacteria isolated and characterized from the fermenting agricultural substrates include Escherichia coli, Pseudomonas aeruginosa, Bacillus polymyxa, Enterobacter aerogenes, Micrococcus roseus, Micrococcus luteus, Citrobacter freundii, Bacillus subtilis, Clostridium perfringens, Bacillus licheniformis, and Bacillus cereus,Proteus mirabilis. The implication of the presence of these bacteria is discussed.