Two different types of bacteria were isolated from the backwash water of a pilot plant of biological filter at Lake Biwa (Japan). Two strains of the bacteria belonging to Pseudomonas sp. and Enterobacter sp. degraded 2-methylisoborneol (2-MIB) to afford 2-methylcamphene and 2-methylenebornane as the dehydration products, and another one belonging to Enterobacter sp. oxidatively decomposed 2-methyleneborane to mainly three degradation products. Camphor and 4,7,7-trimethyl-2-oxabicyclo[2,2,1]-heptan-3-one, together with the above two dehydration products, were identified by the gas chromatographic analysis using unambiguously synthesized authentic compounds.