title: Effects of Bacillus cereus Endospores on Free-Living Protist Growth.
abstract: We studied the predator-prey interactions between heterotrophic protists and endospores of Bacillus cereus group bacteria, in order to gain insight on survival and dispersal of B. cereus endospores in the environment. It has been hypothesised that the spore stage protects against digestion by predating protists. Therefore, experiments were carried out to investigate the impact of B. cereus endospores and vegetative cells, as the only food source, on individual amoeboid, flagellated and ciliated protists. The presence of fluorescent-labelled intracellular bacteria confirmed that B. cereus endospores as well as vegetative cells were ingested by protists and appeared intact in the food vacuoles when observed by epifluorescence microscopy. Furthermore, protist growth and bacterial predation were followed by qPCR. Protists were able to grow on vegetative cells as well as endospores of B. cereus, despite the lower cell division rates observed for some protists when feeding on bacterial endospores. Survival and proliferation of ingested bacteria inside protists cells was also observed. Finally, B. cereus spore germination and growth was observed within all protists with higher abundance in the amoeboid protist after antibiotic treatment of the protist surface. These observations support that protists can act as a potential breeding ground for B. cereus endospores.
authors.affiliation: Department of Environmental Science, Aarhus University, Frederiksborgvej 399, 4000, Roskilde, Denmark.
authors.forename: Susana S
authors.initials: SS
authors.lastname: Santos
authors.affiliation: Department of Environmental Science, Aarhus University, Frederiksborgvej 399, 4000, Roskilde, Denmark.
authors.forename: Niels Bohse
authors.initials: NB
authors.lastname: Hendriksen
authors.affiliation: Department of Bioscience, Aarhus University, Roskilde, Denmark.
authors.forename: Hans Henrik
authors.initials: HH
authors.lastname: Jakobsen
authors.affiliation: Department of Environmental Science, Aarhus University, Frederiksborgvej 399, 4000, Roskilde, Denmark. aw@envs.au.dk.
authors.forename: Anne
authors.initials: A
authors.lastname: Winding
mesh_terms: D000818:Animals; D001409:Bacillus cereus / Q000254:growth & development*; D015169:Colony Count, Microbial; D056890:Eukaryota / Q000378:metabolism*; D011235:Predatory Behavior; D013171:Spores, Bacterial / Q000254:growth & development*
keywords: Bacterivorous protist; Food quality; Growth rates; Ingestion rates; Predator–prey interaction; Soil food web