Potato Crop as a Source of Emetic Bacillus cereus and Cereulide-Induced Mammalian Cell Toxicity

Douwe Hoornstra, Maria A. Andersson, Vera V. Teplova, Raimo Mikkola, Liisa M. Uotila, Leif C. Andersson, Merja Roivainen, Carl G. Gahmberg, Mirja S. Salkinoja-Salonen*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

18 Citations (Scopus)

Abstract

Bacillus cereus, aseptically isolated from potato tubers, were screened for cereulide production and for toxicity on human and other mammalian cells. The cereulide-producing isolates grew slowly, the colonies remained small (similar to 1 mm), tested negative for starch hydrolysis, and varied in productivity from 1 to 100 ng of cereulide mg (wet weight)(-1) (similar to 0.01 to 1 ng per 105 CFU). By DNA-fingerprint analysis, the isolates matched B. cereus F5881/94, connected to human food-borne illness, but were distinct from cereulide-producing endophytes of spruce tree (Picea abies). Exposure to cell extracts (1 to 10 similar to g of bacterial biomass ml(-1)) and to purified cereulide (0.4 to 7 ng ml(-1)) from the potato isolates caused mitochondrial depolarization (loss of Delta Psi m) in human peripheral blood mononuclear cells (PBMC) and keratinocytes (HaCaT), porcine spermatozoa and kidney tubular epithelial cells (PK-15), murine fibroblasts (L-929), and pancreatic insulin-producing cells (MIN-6). Cereulide (10 to 20 ng ml(-1)) exposed pancreatic islets (MIN-6) disintegrated into small pyknotic cells, followed by necrotic death. Necrotic death in other test cells was observed only after a 2-log-higher exposure. Exposure to 30 to 60 ng of cereulide ml-1 induced K+ translocation in intact, live PBMC, keratinocytes, and sperm cells within seconds of exposure, depleting 2 to 10% of the cellular K+ stores within 10 min. The ability of cereulide to transfer K+ ions across biological membranes may benefit the producer bacterium in K+ -deficient environments such as extracellular spaces inside plant tissue but is a pathogenic trait when in contact with mammalian cells.

Original languageEnglish
Pages (from-to)3534-3543
Number of pages10
JournalApplied and Environmental Microbiology
Volume79
Issue number12
DOIs
Publication statusPublished - Jun 2013
MoE publication typeA1 Journal article-refereed

Keywords

  • QUANTITATIVE-ANALYSIS
  • TOXIN
  • FOOD
  • STRAINS
  • POTASSIUM
  • DIVERSITY
  • ENVIRONMENTS
  • VALINOMYCIN
  • PREVALENCE
  • ACTIVATION

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