Abstract
The antibiotic-resistant bacterium Paenibacillus larvae is the causative agent of American foulbrood (AFB), currently the most destructive bacterial disease in honeybees. Phages that infect P. larvae were isolated as early as the 1950s, but it is only in recent years that P. larvae phage genomes have been sequenced and annotated. In this study we analyze the genomes of all 48 currently sequenced P. larvae phage genomes and classify them into four clusters and a singleton. The majority of P. larvae phage genomes are in the 38–45 kbp range and use the cohesive ends (cos) DNA-packaging strategy, while a minority have genomes in the 50–55 kbp range that use the direct terminal repeat (DTR) DNA-packaging strategy. The DTR phages form a distinct cluster, while the cos phages form three clusters and a singleton. Putative functions were identified for about half of all phage proteins. Structural and assembly proteins are located at the front of the genome and tend to be conserved within clusters, whereas regulatory and replication proteins are located in the middle and rear of the genome and are not conserved, even within clusters. All P. larvae phage genomes contain a conserved N-acetylmuramoyl-l-alanine amidase that serves as an endolysin.
Highlights
The gram-positive, spore-forming bacterium Paenibacillus larvae is the causative agent of American foulbrood (AFB), the most destructive bacterial disease in honeybees (Apis mellifera) and one of the leading causes of their global population decline [1]
Rearranging the genome in this manner resulted in the start of the small terminase gene being located 50 base pairs downstream of base 1, consistent with most published P. larvae phage genomes
P. larvae phages were isolated from sources such as soil underneath hives, beehive products, bees, and beeswax-containing commercial products
Summary
The gram-positive, spore-forming bacterium Paenibacillus larvae is the causative agent of American foulbrood (AFB), the most destructive bacterial disease in honeybees (Apis mellifera) and one of the leading causes of their global population decline [1]. P. larvae exclusively infects honeybee larvae and not adult bees, it is highly virulent and can wipe out an infected hive in a matter of days if untreated [1]. P. larvae spores are spread by bees and the wind, and AFB is highly contagious. P. larvae spores are extremely durable, lasting several decades [1]. In recent years several P. larvae strains have developed antibiotic resistance, complicating treatment efforts [2,3,4]. If the infection does not clear, incineration of infected hives is the only method for combating P. larvae outbreaks
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