Characterization Of Enterococcus Durans Edd2, A Strain From Beehives With Inhibitory Activity Against Paenibacillus Larvae

In this research, we report the isolation of Enterococcus durans EDD2, which showed strong inhibitory activity against Paenibacillus larvae, the causative agent of the American foulbrood disease (AFB). The strain was found in freshly collected pollen granules from four beehives in Dushantzi village (Pirdop region, Bulgaria), and was determined by polyphase approach including molecular, biochemical, and physiological tests. Whole-genome sequencing by the Illumina HiSeq NGS platform with 2 x 150 bases paired-end reads revealed the presence of two contigs containing genetic determinants for Enterocin L50A/L50B and Enterocin P -like bacteriocins, the first ones being carried out by the chromosome, while the second one being present on a putative plasmid. E. durans EDD2 was also subjected to genetic and microbiological tests for several pathogenicity factors, and none was found. These results, combined with the fact that the strain was present in four, but not all of the 15 beehives in the apiary, suggest that it is not a result from some human or animal fecal or other types of contamination in the adjacent fields, but rather it is maintained within the bees microbiomes and was transferred to the pollen granules by the insects' saliva. It was proven that E. durans EDD2 possesses a strong probiotic inhibitory activity against P. larvae due to the production of bacteriocins.