title: Requirements for in vitro germination of Paenibacillus larvae spores.
abstract: Paenibacillus larvae is the causative agent of American foulbrood (AFB), a disease affecting honey bee larvae. First- and second-instar larvae become infected when they ingest food contaminated with P. larvae spores. The spores then germinate into vegetative cells that proliferate in the midgut of the honey bee. Although AFB affects honey bees only in the larval stage, P. larvae spores can be distributed throughout the hive. Because spore germination is critical for AFB establishment, we analyzed the requirements for P. larvae spore germination in vitro. We found that P. larvae spores germinated only in response to l-tyrosine plus uric acid under physiologic pH and temperature conditions. This suggests that the simultaneous presence of these signals is necessary for spore germination in vivo. Furthermore, the germination profiles of environmentally derived spores were identical to those of spores from a biochemically typed strain. Because l-tyrosine and uric acid are the only required germinants in vitro, we screened amino acid and purine analogs for their ability to act as antagonists of P. larvae spore germination. Indole and phenol, the side chains of tyrosine and tryptophan, strongly inhibited P. larvae spore germination. Methylation of the N-1 (but not the C-3) position of indole eliminated its ability to inhibit germination. Identification of the activators and inhibitors of P. larvae spore germination provides a basis for developing new tools to control AFB.
authors.affiliation: School of Life Sciences, University of Nevada, Las Vegas, Las Vegas, Nevada, USA.
authors.forename: Israel
authors.initials: I
authors.lastname: Alvarado
authors.forename: Andy
authors.initials: A
authors.lastname: Phui
authors.forename: Michelle M
authors.initials: MM
authors.lastname: Elekonich
authors.forename: Ernesto
authors.initials: E
authors.lastname: Abel-Santos
mesh_terms: D000818:Animals; D001516:Bees / Q000382:microbiology; D003470:Culture Media; D007211:Indoles / Q000494:pharmacology; D007814:Larva / Q000382:microbiology; D056507:Paenibacillus / Q000187:drug effects* / Q000502:physiology*; D019800:Phenol / Q000494:pharmacology; D013171:Spores, Bacterial / Q000502:physiology*; D013696:Temperature; D014443:Tyrosine / Q000494:pharmacology; D014527:Uric Acid / Q000494:pharmacology
chemical_list: D003470:Culture Media; D007211:Indoles; D014527:Uric Acid; D019800:Phenol; D014443:Tyrosine; C030374:indole