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Antimicrobial Agents and Chemotherapy, August 1998, p. 1906-1910, Vol. 42, No. 8
Institute of Dentistry and Turku Immunology
Centre1 and
Department of
Biotechnology,2 University of Turku,
FIN-20520 Turku, Finland
Received 30 September 1997/Returned for modification 31 January
1998/Accepted 27 April 1998
The oral bacterium Streptococcus mutans was transformed
by electroporation with a shuttle vector (pCSS945) containing insect luciferase gene from a click beetle (Pyrophorus
plagiophthalamus) resulting in a bioluminescent phenotype. This
S. mutans strain was used in experiments in which light
emission was used as a rapid and, compared to conventional CFU
counting, more convenient means of estimating the effects of various
antimicrobial treatments. The basic parameters affecting in vivo light
production by the strain were studied. It was found that pH 6.0 was
optimal for incorporation of the substrate D-luciferin for
the luciferase reaction. The optimum concentration of
D-luciferin was approximately 150 µM at room temperature.
Under optimum conditions the light emission in vivo increased
rapidly to a constant level and thereafter had a decay of 0.6%/min
when logarithmic-growth-phase cells were used. The light emission
closely paralleled the numbers of CFU, giving a detectable signal from
30,000 cells and having a dynamic measurement range over 4 log
CFU/relative light unit. The cells were treated with various
antimicrobial agents, and the emitted bioluminescence was
measured. With the bioluminescent measurements, the results were
obtained within hours compared to the days required for agar plates,
and also, the kinetics of the antibacterial actions could be followed.
Thus, the light emission was found to be a reliable, sensitive, and
real-time indicator of the bacteriostatic actions of the antimicrobial
agents tested.
0066-4804/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Generation of Bioluminescent Streptococcus
mutans and Its Usage in Rapid Analysis of the Efficacy of
Antimicrobial Compounds
and
*
Corresponding author. Mailing address: Institute
of Dentistry and Turku Immunology Centre, University of Turku,
Lemminkäisenkatu 2, FIN-20520 Turku, Finland. Phone:
358-2-3337918. Fax: 358-2-3338356. E-mail:
vuokko.loimaranta{at}utu.fi.
Present address: Department of Oral Medical and Surgical Sciences,
Faculty of Dentistry, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3.
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