Influence of interactions between temperature, ferric ammonium citrate and glycine betaine on the growth of Listeria monocytogenes in a defined medium.
OBJECTIVE
To investigate interactions, if any, between temperature, ferric ammonium citrate and glycine betaine on the growth of Listeria monocytogenes in modified Pine's medium (Pine et al. 1989).


RESULTS
Modified Pine's medium containing 0, 0.044, 0.088 or 0.176 g l(-1) ferric ammonium citrate, and 0 or 1 mM glycine betaine, was inoculated with each of two L. monocytogenes strains and incubated at 4, 25 or 37 degrees C. The optical density at 600 nm, and cell numbers, were determined at appropriate time intervals. At 4 degrees C, but not other temperatures, increasing ferric ammonium citrate resulted in improved growth in the absence, but not the presence, of glycine betaine. The presence of glycine betaine was inhibitory at 25 and 37 degrees C, but not at 4 degrees C.


CONCLUSIONS
Interactions affecting the growth kinetics of L. monocytogenes were apparent between the parameters investigated.


CONCLUSIONS
Limitations on the use of modified Pine's medium, and the significance of iron metabolism at lower temperatures, were revealed.
Dykes
G A
GA
Department of Applied Microbiology and Food Science, University of Saskatchewan, 51 Campus Drive, Saskatoon SK S7N 5A8, Canada. gary.dykes@foodscience.afisc.csiro.au
Dworaczek
M
M
D001622:Betaine / Q000378:metabolism*; D003470:Culture Media; D005290:Ferric Compounds / Q000378:metabolism*; D007700:Kinetics; D008089:Listeria monocytogenes / Q000254:growth & development*; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*; D013696:Temperature
D003470:Culture Media; D005290:Ferric Compounds; D000644:Quaternary Ammonium Compounds; D001622:Betaine; C013531:ferric ammonium citrate