Abstract: Ten kinds of bacterium were isolated from Stichopus japonicus, in which six gram negative bacteria and four gram positive bacteria. The morphology, physiological and biochemical characteristics of these bacterium were studied and showed that these bacteria are three kinds Corynebacterium species, Psychrobacter phenylpyruvica, Staphylococcus warneri, Moraxella osloesi, Yersinia pestis, Flavimonas oryzihabitans, Actinobacillus ureae, Sphingomonas paucimobilis, in which the five late were considered as pathogens or conditional pathogens. The activity of ectonenzym of bacteriums were studied and showed that all these bacteria cannot decompose ester, but can decompose protein at certain extent. Many kinds of pathogens affect the Stichopus japonicus’s edible and safe value, and also they are the important factor of that Stichopus japonicus are decomposed easily.

Key words: Stichopus japonicus, bacterium, isolation and characterization