Effects of Bacillus cereus Endospores on Free-Living Protist Growth

TY - JOUR

T1 - Effects of Bacillus cereus Endospores on Free-Living Protist Growth

AU - Santos, Susana S

AU - Hendriksen, Niels Bohse

AU - Jakobsen, Hans Henrik

AU - Winding, Anne

PY - 2017/3/16

Y1 - 2017/3/16

N2 - 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.

AB - 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.

KW - Bacterivorous protist

KW - Food quality

KW - Growth rates

KW - Ingestion rates

KW - Predator–prey interaction

KW - Soil food web

UR - http://www.scopus.com/inward/record.url?scp=85001698802&partnerID=8YFLogxK

U2 - 10.1007/s00248-016-0905-7

DO - 10.1007/s00248-016-0905-7

M3 - Journal article

C2 - 27928597

SN - 0095-3628

VL - 73

SP - 699

EP - 709

JO - Microbial Ecology

JF - Microbial Ecology

IS - 3

ER -