Abstract: Six strains of organic matter degrading bacteria were screened from environment of rice-crayfish co-culture（RCIS）, all of which were identified as Bacillus sp.. Among them, OC-1, OC-2, OC-3 and OC-6 were all classified as Bacillus aryabhatta, OC-4 was identified as Bacillus flexus, and OC-5 was identified as Bacillus marisflavi. These strains can efficiently degrade organic matter andammonia in the bait culture medium, and the COD degradation rate of these strains was more than 85% after three days of cultivation. OD-1, OD-2 can quickly and efficiently degrade the organic matter in bait culture medium. The high degradation efficiency may be related to its ability to secrete a variety of extracellular enzymes. These two strains had application potential.

Key words: rice-crayfish co-culture （RCIS）, organic matter degrading bacteria, extracellular enzymes