Association of toxin-producing Clostridium botulinum with the macroalga Cladophora in the Great Lakes

Chan Lan Chun, Urs Ochsner, Muruleedhara N. Byappanahalli, Richard L. Whitman, William H. Tepp, Guangyun Lin, Eric A. Johnson, Julie Peller, Michael J. Sadowsky

Research output: Contribution to journalArticle

29 Scopus citations

Abstract

Avian botulism, a paralytic disease of birds, often occurs on a yearly cycle and is increasingly becoming more common in the Great Lakes. Outbreaks are caused by bird ingestion of neurotoxins produced by Clostridium botulinum, a spore-forming, gram-positive, anaerobe. The nuisance, macrophytic, green alga Cladophora (Chlorophyta; mostly Cladophora glomerata L.) is a potential habitat for the growth of C. botulinum. A high incidence of botulism in shoreline birds at Sleeping Bear Dunes National Lakeshore (SLBE) in Lake Michigan coincides with increasingly massive accumulations of Cladophora in nearshore waters. In this study, free-floating algal mats were collected from SLBE and other shorelines of the Great Lakes between June and October 2011. The abundance of C. botulinum in algal mats was quantified and the type of botulism neurotoxin (bont) genes associated with this organism were determined by using most-probable-number PCR (MPN-PCR) and five distinct bont gene-specific primers (A, B, C, E, and F). The MPN-PCR results showed that 16 of 22 (73%) algal mats from the SLBE and 23 of 31(74%) algal mats from other shorelines of the Great Lakes contained the bont type E (bont/E) gene. C. botulinum was present up to 15 000 MPN per gram dried algae based on gene copies of bont/E. In addition, genes for bont/A and bont/B, which are commonly associated with human diseases, were detected in a few algal samples. Moreover, C. botulinum was present as vegetative cells rather than as dormant spores in Cladophora mats. Mouse toxin assays done using supernatants from enrichment of Cladophora containing high densities of C. botulinum (>1000 MPN/g dried algae) showed that Cladophora-borne C. botulinum were toxin-producing species (BoNT/E). Our results indicate that Cladophora provides a habitat for C. botulinum, warranting additional studies to better understand the relationship between this bacterium and the alga, and how this interaction potentially contributes to botulism outbreaks in birds.

Original languageEnglish (US)
Pages (from-to)2587-2594
Number of pages8
JournalEnvironmental Science and Technology
Volume47
Issue number6
DOIs
StatePublished - Mar 19 2013

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