AUTHOR=Cui Pu , Wu Haoyang , Jiang Taoshan , Tao Jian , Zhu Zhiwei , Liu Peng , Yu Linsheng , Zhang Yinglao 

TITLE=Diversity and antibacterial potential of the Actinobacteria associated with Apis mellifera ligustica

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.1056176

DOI=10.3389/fmicb.2022.1056176

ISSN=1664-302X

ABSTRACT=<p>Insect-associated Actinobacteria are a potentially rich source of novel natural products with antibacterial activity. Here, the community composition of Actinobacteria associated with <italic>Apis mellifera ligustica</italic> was investigated by integrated culture-dependent and independent methods. A total of 61 strains of <italic>Streptomyces</italic> genera were isolated from the honeycomb, larva, and different anatomical parts of the honeybee’s body using the culture-dependent method. Amplicon sequencing analyses revealed that the actinobacterial communities were dominated by the family of Bifidobacteriaceae and Microbacteriaceae in the honeybee gut, and Nocardiaceae and Pseudonocardiaceae in the honeycomb, whereas only <italic>Streptomyces</italic> genera were isolated by the culture-dependent method. Culture-independent analyses showed more diverse actinobacterial communities than those of culture-dependent methods. The antibacterial bioassay showed that most crude extracts of representative isolates exhibited antibacterial activities. Among them, the crude extract of <italic>Streptomyces</italic> sp. FCF01 showed the best antibacterial activities against <italic>Staphylococcus aureus</italic>, <italic>Micrococcus tetragenus</italic>, and <italic>Pseudomonas syringae</italic> pv. <italic>actinidiae</italic> (Psa) with the disc diameter of inhibition zone diameter (IZD) of 23.00, 15.00, and 13.33 mm, respectively. Chemical analysis of <italic>Streptomyces</italic> sp. FCF01 led to the isolation of three secondary metabolites, including mayamycin (<bold>1</bold>), mayamycin B (<bold>2</bold>), and N-(2-Hydroxyphenyl) acetamide (<bold>3</bold>). Among them, compound <bold>1</bold> displayed strong antibacterial activity against <italic>S. aureus</italic>, <italic>M. tetragenus</italic>, and Psa with minimum inhibitory concentrations (MIC) values of 6.25, 12.5, and 6.25 μg/ml, respectively. In addition, two novel derivative compounds <bold>1a</bold> and <bold>1b</bold> were synthesized by acetylation of compound <bold>1</bold>. Both compounds <bold>1a</bold> and <bold>1b</bold> displayed similar antibacterial activities with those of metabolite <bold>1</bold>. These results indicated that <italic>Streptomyces</italic> species associated with honeybees had great potential in finding antibiotics.</p>