Diversity and antimicrobial activities of culturable actinomycetes from Odontotermes formosanus (Blattaria: Termitidae)

Background Actinomycetes are important microbes, and they are very important for developing active substances for useful drugs. Actinomycetes are numerous inhabitants, and they are widely distributed in the nest of fungus-growing termites. Previously, we isolated and purified numerous actinomycetes from the combs of Odontotermes formosanus and obtained a variety of valuable natural products. Results Here, we isolated and purified actinomycetes from fungus-growing termite Odontotermes formosanus using medium-based cultures. Among the eight media tested, M7 and I-HV media were found suitable for isolating actinomycetes. Further, 84 actinomycetes, including 79 Streptomyces isolates, were isolated and purified from O. formosanus and its combs, which belong to four genera (Streptomyces, Kribbella, Amycolatopsis, and Cellulosimicrobium). Then, the type and quantity of actinomycetes were positively correlated with the activity range of termites. Twenty-two actinomycetes strains showed antimicrobial activities. Among them, the BYF18, BYF48, BYF70, and BYF106 strains exhibited antifungal activities against five pathogenic fungi, with zone of inhibition (ZOI) values ranging from 3 to 21 mm. Grincamycin N was isolated and purified from the metabolites of Streptomyces lannensis (BYF106), and it displayed antibacterial activities against Staphylococcus aureus (ZOI = 13.82 +/- 0.52 mm) and Micrococcus tetragenus (ZOI = 17.6 +/- 0.5 mm) (gentamycin sulfate, as the positive control, had ZOI values of 19.9 +/- 0.5 mm and 30.83 +/- 0.75 mm, against S. aureus and M. tetragenus, respectively). Conclusions Our results confirmed that the actinomycetes associated with O. formosanus are important sources of new active substances.

Automated summary

In this study, actinomycetes were isolated and purified from the combs of the fungus-growing termite Odontotermes formosanus. The type and quantity of actinomycetes were found to be positively correlated with the activity range of the termites. Some strains exhibited antimicrobial activities, such as Grincamycin N from Streptomyces lannensis, which displayed antibacterial activities against Staphylococcus aureus and Micrococcus tetragenus. These results confirm that the actinomycetes associated with O. formosanus are important sources of new active substances.