Phylogenomic analysis of Paenibacillus larvae isolates from Slovakia predicts regional genomic clustering
The Paenibacillus larvae is known as the causative agent of American foulbrood, which is widespread throughout the world. It is a highly contagious, fatal disease of honeybees. The aim of this study was to investigate the phylogenomic relationships of ERIC II genotype P. larvae isolates from Slovakia and to compare them with ERIC II genotype isolates originating from other countries. Phylogenomic analyses of P. larvae D3, 5S, and M1 isolates from Slovakia revealed a very low level of genetic diversity among our isolates, with low genome size variability (3.56 ± 0.04 Mbp) and average nucleotide and amino acid identity levels above 99%. Genomes showed similar gene counts (3,700 ± 59 genes per genome), with the highest variability in the mobile elements, especially bacteriophage-related genes (from 220 to 281 genes per genome). Comparative genomic analyses of several ERIC II and ERIC I types of P. larvae genomes available in the GenBank showed a clear geographical pattern, indicating that P. larvae strains spreading in the Slovak region differ from strains found in other parts of Europe and the rest of the world, thus indicating the possible existence of regionalism in the P. larvae species distribution.