title: An automated technique for most-probable-number (MPN) analysis of densities of phagotrophic protists with lux AB labelled bacteria as growth medium.
abstract: An automated modification of the most-probable-number (MPN) technique has been developed for enumeration of phagotrophic protozoa. The method is based on detection of prey depletion in micro titre plates rather than on presence of protozoa. A transconjugant Pseudomonas fluorescens DR54 labelled with a luxAB gene cassette was constructed, and used as growth medium for the protozoa in the micro titre plates. The transconjugant produced high amounts of luciferase which was stable and allowed detection for at least 8 weeks. Dilution series of protozoan cultures and soil suspensions were inoculated into micro titre plates amended with a suspension of the transconjugant. After 45 days measurement of light emission allowed detection of individual wells in the titre plates, where protozoan grazing had removed the inoculated bacteria.
authors.affiliation: Terrestrial Ecology, Zoological Institute, University of Copenhagen, Denmark. fekelund@zi.ku.dk
authors.forename: F
authors.initials: F
authors.lastname: Ekelund
authors.forename: S
authors.initials: S
authors.lastname: Christensen
authors.forename: R
authors.initials: R
authors.lastname: Rønn
authors.forename: E
authors.initials: E
authors.lastname: Buhl
authors.forename: C S
authors.initials: CS
authors.lastname: Jacobsen
mesh_terms: D000818:Animals; D001322:Autoanalysis; D015169:Colony Count, Microbial / Q000379:methods; D003470:Culture Media; D056890:Eukaryota / Q000254:growth & development*; D008156:Luciferases / Q000096:biosynthesis; D008163:Luminescent Measurements; D011551:Pseudomonas fluorescens / Q000201:enzymology / Q000235:genetics; D012988:Soil Microbiology
chemical_list: D003470:Culture Media; D008156:Luciferases