Diversity, antibacterial and phytotoxic activities of actinomycetes associated with Periplaneta fuliginosa .

Background: Insect-associated actinomycetes represent a potentially rich source for discovering bioactive metabolites. However, the diversity, antibacterial and phytotoxic activities of symbiotic actinomycetes associated with Periplaneta fuliginosa have not yet been conducted.
Results: A total of 86 strains of actinomycetes were isolated from the cornicles and intestines of both nymphs and adults of P. fuliginosa . Diversity analysis revealed that the isolated strains were preliminarily identified as 17 species from two genera, and the dominant genus was Streptomyces . A total of 36 crude extracts (60%) obtained from the supernatant of the 60 fermented strains exhibited a potent antibacterial activity against at least one tested pathogenic bacterium. Among these active strains, 27 crude extracts (75%) exhibited phytotoxic activity against the radicle of Echinochloa crusgalli . Furthermore, seven known compounds, including methoxynicotine ( 1 ), (3Z,6Z)-3-(4-methoxybenzylidene)-6-(2-methylpropyl) piperazine-2,5-dione ( 2 ), XR334 ( 3 ), 1-hydroxy-4-methoxy-2-naphthoic acid ( 4 ), nocapyrone A ( 5 ), β-daucosterol ( 6 ), and β-sitosterol ( 7 ) were isolated from an active rare actinomycete Nocardiopsis sp. ZLC-87 which was isolated from the gut of adult P. fuliginosa . Among them, compound 4 exhibited moderate antibacterial activity against Micrococcus tetragenus , Staphylococcus aureus , Escherichia coli , and Pseudomonas syringae pv. actinidiae with the zone of inhibition (ZOI) of 14.5, 12.0, 12.5, and 13.0 mm at a concentration of 30 μg/disc, respectively, which was weaker than those of gentamicin sulfate (ZOI of 29.5, 19.0, 18.5, and 24.5 mm). In addition, the compound 4 had potent phytotoxic activity against the radicle of E. crusgalli and Abutilon theophrasti with the inhibition rate of 65.25% and 92.68% at the concentration of 100 μg/mL.
Conclusion: Based on these findings, this study showed that P. fuliginosa -associated actinomycetes held promise for the development of new antibiotic and herbicide resources.
Competing Interests: The authors declare that they have no competing interests.
(© 2024 Liu et al.)