A PCR-Based Method for Distinguishing between Two Common Beehive Bacteria, Paenibacillus larvae and Brevibacillus laterosporus

Paenibacillus larvae and Brevibacillus laterosporus are two bacteria that are members of the Paenibacillaceae family. Both are commonly found in beehives and have historically been difficult to distinguish from each other due to related genetic and phenotypic characteristics and a shared ecological niche. Here, we discuss the likely mischaracterization of three 165 rRNA sequences previously published as P. larvae and provide the phylogenetic evidence that supported the GenBank reassignment of the sequences as B. laterosporus. We explore the issues that arise by using only 165 rRNA or other single-gene analyses to distinguish between these bacteria. We also present three sets of molecular markers, two sets that distinguish P. larvae from B. laterosporus and other closely related species within the Paenibacillus genus and a third set that distinguishes B. laterosporus from P. larvae and other closely related species within the Brevibacillus genus. These molecular markers provide a tool for proper identification of these oft-mistaken species. IMPORTANCE 165 rRNA gene sequencing in bacteria has long been held as the gold standard for typing bacteria and, for the most part, is an excellent method of taxonomically identifying different bacterial species. However, the high level of 165 rRNA sequence similarity of some published strains of P. larvae and B. laterosporus, as well as possible horizontal gene transfer events within their shared ecological niche, complicates the use of 165 rRNA sequence as an effective molecular marker for differentiating these two species. Additionally, shared characteristics of these bacteria limit the effectiveness of using traditional phenotypic identification assays, such as the catalase test. The results from this study provide PCR methods to quickly differentiate between these two genera and will be useful when studying Brevibacillus, Paenibacillus, and other disease-relevant bacteria commonly found in beehives.