title: Potato crop as a source of emetic Bacillus cereus and cereulide-induced mammalian cell toxicity.
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 (~1 mm), tested negative for starch hydrolysis, and varied in productivity from 1 to 100 ng of cereulide mg (wet weight)(-1) (~0.01 to 1 ng per 10(5) 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 μg 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 ΔΨm) 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.
authors.affiliation: Department of Food and Environmental Sciences (Microbiology), Helsinki University, Helsinki, Finland.
authors.forename: Douwe
authors.initials: D
authors.lastname: Hoornstra
authors.forename: Maria A
authors.initials: MA
authors.lastname: Andersson
authors.forename: Vera V
authors.initials: VV
authors.lastname: Teplova
authors.forename: Raimo
authors.initials: R
authors.lastname: Mikkola
authors.forename: Liisa M
authors.initials: LM
authors.lastname: Uotila
authors.forename: Leif C
authors.initials: LC
authors.lastname: Andersson
authors.forename: Merja
authors.initials: M
authors.lastname: Roivainen
authors.forename: Carl G
authors.initials: CG
authors.lastname: Gahmberg
authors.forename: Mirja S
authors.initials: MS
authors.lastname: Salkinoja-Salonen
mesh_terms: D000818:Animals; D001409:Bacillus cereus / Q000737:chemistry*; D047630:Depsipeptides / Q000378:metabolism* / Q000633:toxicity; D004639:Emetics / Q000378:metabolism* / Q000633:toxicity; D004847:Epithelial Cells / Q000187:drug effects; D006801:Humans; D050417:Insulin-Secreting Cells / Q000187:drug effects; D015603:Keratinocytes / Q000187:drug effects; D007684:Kidney Tubules / Q000166:cytology; D007963:Leukocytes, Mononuclear / Q000187:drug effects; D008297:Male; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D011198:Solanum tuberosum / Q000254:growth & development / Q000382:microbiology*; D013094:Spermatozoa / Q000187:drug effects; D013552:Swine; D013997:Time Factors; D018675:Toxicity Tests
chemical_list: D047630:Depsipeptides; D004639:Emetics; C089294:cereulide