Antimicrobial activity of spp. isolated from combs against some phytopathogenic bacteria.

The aim of this study was to investigate the antimicrobial potential of actinomycetes isolated from combs of the giant honey bee, . In total, 25 isolates were obtained from three different media and were screened for antimicrobial activity against four plant pathogenic bacteria (, pv. , pv. and ). Following screening using a cross-streaking method, three isolates showed the potential to inhibit the growth of plant pathogenic bacteria. Based on a 96-well microtiter assay, the crude extract of DSC3-6 had minimum inhibitory concentration (MIC) values against pv. , pv. , and of 16, 32, 32 and 64 mg L, respectively. The crude extract of DGA3-20 had MIC values against pv. , pv. , and of 32, 32, 32 and 64 mg L, respectively. The crude extract of DGA8-3 at 32 mgL inhibited the growth of pv. , pv. , and . Based on their 16S rRNA gene sequences, all isolates were identified as members of the genus . The analysis of 16S rRNA gene sequence similarity and of the phylogenetic tree based on the maximum likelihood algorithm showed that isolates DSC3-6, DGA3-20 and DGA8-3 were closely related to (99.42%), (99.70%) and (99.71%), respectively. This was the first report on antibacterial activity against phytopathogenic bacteria from actinomycetes isolated from the giant honey bee.