Environmental Microbiology
Environmental Microbiology
5 years ago

Neurotoxin synthesis is positively regulated by the sporulation transcription factor Spo0A in Clostridium botulinum type E

Hannu Korkeala, Miia Lindström, Gerald Mascher, Anna Mertaoja
Clostridium botulinum produces the most potent natural toxin, the botulinum neurotoxin (BoNT), probably to create anaerobiosis and nutrients by killing the host, and forms endospores that facilitate survival in harsh conditions and transmission. Peak BoNT production coincides with initiation of sporulation in C. botulinum cultures, which suggests common regulation. Here we show that Spo0A, the master regulator of sporulation, positively regulates BoNT production. Insertional inactivation of spo0A in C. botulinum type E strain Beluga resulted in significantly reduced BoNT production and in abolished or highly reduced sporulation in relation to wild-type controls. Complementation with spo0A restored BoNT production and sporulation. Recombinant DNA binding domain of Spo0A directly bound to a putative Spo0A binding box (CTTCGAA) within the BoNT/E operon promoter, demonstrating direct regulation. Spo0A is the first neurotoxin regulator reported in C. botulinum type E. Unlike other C. botulinum strains that are terrestrial and employ the alternative sigma factor BotR in directing BoNT expression, C. botulinum type E strains are adapted to aquatic ecosystems, possess distinct epidemiology, and lack BotR. Our results provide fundamental new knowledge on the genetic control of BoNT production and demonstrate common regulation of BoNT production and sporulation, providing a key intervention point for control. This article is protected by copyright. All rights reserved.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1111/1462-2920.13892

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