Actinomycetes have attracted a lot of interest as the main producer of secondary metabolites and industrial antibiotics in biotechnology. There are more than 22,000 known microbial secondary metabolites, 70% of which are produced by actinomycetes. The aims of this study were the isolation and characterization of symbiotic actinomycetes with some invertebrates in Mazandaran and their ability to produce antimicrobial compounds. For isolation of actinomycetes, some invertebrate animals including crabs, earthworms, snails and shrimps were collected then the gastrointestinal tracts were separated. They were kept at temperature 50-60 °C for 24 hours. After its dilution in a saline buffer solution, the samples were inoculated on Starch Casein Agar (SCA) selective medium and tryptone soy agar (TSA). The plates were incubated for 21 days at 28 °C. Putative colonies of actinomycetes with a tough or powdery texture were isolated. Then crude extract was taken from the growth culture of active isolates. The antimicrobial activities of the extracts were examined against some pathogenic bacteria using the disc diffusion method. The results demonstrated that the crude extracts of these isolates showed well antibacterial activity against Escherichia coli, Shigella sonnei, Salmonella typhi and Klebsiella pneumoniae. These results revealed that invertebrates hold the potential to have a diversity of actinomycetes with antimicrobial properties.
