Abstract: 【Aim】 In view of the strong adaptability of Periplaneta americana in harsh environments, this study aims to isolate and screen actinomycetes with antibacterial activity from the gut of P. americana adults in the wild in Dali prefecture of Yunnan province so as to provide strain resources for the development of antibiotics. 【Methods】 The gut actinomycetes of P. americana adults were isolated by coating plate method and plate marking method, and six strains of common human pathogenic bacteria, Staphylococcus aureus, methicillin-resistant S. aureus, Pseudomonas aeruginosa, Enterococcus faecalis, Escherichia coli and Salmonella typhimurium, were used as the indicator strains. The antibacterial activities of the secondary metabolites extracted from these actinomycetes were determined by the Oxford cup method. The actinomycetes with broad spectrum and obvious antibacterial activities were identified according to their morphological features as well as 16S rRNA gene sequence analysis. Their taxonomic statuses were confirmed by the BLAST analysis of their 16S rRNA gene sequences and phylogenetic analysis. 【Results】 Totally, 41 actinomycetes strains were isolated from the gut of P. americana adults. The results of antibacterial activity test showed that 34 strains (82.9%) of actinomycetes had inhibitory activities against at least one indicator pathogenic bacterium. Among them, seven strains had inhibitory activities against more than three pathogenic bacteria, and nine strains had obvious antibacterial activities. Based on the results of phylogenetic analysis, these actinomycetes were identified as Streptomyces spp. 【Conclusion】 The gut of P. americana adults in the wild contains rich actinomycete resources with antibacterial activity, which provides an important microbial source for further exploration of new antibiotics.

Key words: Periplaneta americana, gut actinomycetes, antibacterial activity, 16S rRNA, molecular identification