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Bacteriophage. 2011 May-Jun; 1(3): 143–151.
Published online May 1, 2011. doi:  10.4161/bact.1.3.16710
PMCID: PMC3225779
Reporter bacteriophage A511::celB transduces a hyperthermostable glycosidase from Pyrococcus furiosus for rapid and simple detection of viable Listeria cells
Steven Hagens,1 Tomas de Wouters, Philip Vollenweider, and Martin J Loessnercorresponding author
Institute of Food, Nutrition and Health; ETH Zurich; Zurich, Switzerland
corresponding authorCorresponding author.
1Current Address: Micreos; Nieuwe Kanaal 7P; Wageningen, The Netherlands
Correspondence to: Martin J. Loessner; Email: martin.loessner/at/
Received April 6, 2011; Revised May 11, 2011; Accepted June 9, 2011.
Reporter bacteriophages for detection of pathogenic bacteria offer fast and sensitive screening for live bacterial targets. We present a novel strategy employing a gene encoding a hyperthermophilic enzyme, permitting the use of various substrates and assay formats. The celB gene from the hyperthermophilic archaeon Pyrococcus furiosus specifying an extremely thermostable β-glycosidase was inserted into the genome of the broad host range, virulent Listeria phage A511 by homologous recombination. It is expressed at the end of the infectious cycle, under control of the strong major capsid gene promoter Pcps. Infection of Listeria with A511::celB results in strong gene expression and synthesis of a fully functional β-glycosidase. The reporter phage was tested for detection of viable Listeria cells with different chromogenic, fluorescent or chemiluminescent substrates. The best signal-to-noise ratio and sufficiently high sensitivity was obtained using the inexpensive substrate 4-Methylumbelliferyl-α-D-Glucopyranoside (MUG). The reporter phage assay is simple to perform and can be completed in about 6 h. Phage infection, as well as the subsequent temperature shift, enzymatic substrate conversion and signal recordings are independent from each other and may be performed separately. The detection limit for viable Listeria monocytogenes in an assay format adapted to 96-well microplates was 7.2 × 102 cells per well, corresponding to 6 × 103 cfu per ml in suspension. Application of the A511::celB protocol to Listeria in spiked chocolate milk and salmon demonstrate the usefulness of the reporter phage for rapid detection of low numbers of the bacteria (10 cfu/g or less) in contaminated foods.
Key words: Listeria monocytogenes, reporter bacteriophage, Pyrococcus furiosus, glycosidase, celB, rapid methods, food safety
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