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Applied and Environmental Microbiology, June 2005, p. 3248-3254, Vol. 71, No. 6
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.6.3248-3254.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Influence of Glutamate on Growth, Sporulation, and Spore Properties of Bacillus cereus ATCC 14579 in Defined Medium

Ynte P. de Vries,^1,2,3* Ratna D. Atmadja,² Luc M. Hornstra,^1,3 Willem M. de Vos,¹ and Tjakko Abee^1,2

Wageningen Centre for Food Sciences, Wageningen, The Netherlands,¹ Laboratory of Food Microbiology, Wageningen UR, Wageningen, The Netherlands,² Agrotechnology and Food Innovations, Wageningen, The Netherlands³

Received 19 July 2004/ Accepted 27 December 2004

A chemically defined medium in combination with an airlift fermentor system was used to study the growth and sporulation of Bacillus cereus ATCC 14579. The medium contained six amino acids and lactate as the main carbon sources. The amino acids were depleted during exponential growth, while lactate was metabolized mainly during stationary phase. Two concentrations of glutamate were used: high (20 mM; YLHG) and low (2.5 mM; YLLG). Under both conditions, sporulation was complete and synchronous. Sporulation started and was completed while significant amounts of carbon and nitrogen sources were still present in the medium, indicating that starvation was not the trigger for sporulation. Analysis of amino acids and NH₄⁺ in the culture supernatant showed that most of the nitrogen assimilated by the bacteria was taken up during sporulation. The consumption of glutamate depended on the initial concentration; in YLLG, all of the glutamate was used early during exponential growth, while in YLHG, almost all of the glutamate was used during sporulation. In YLLG, but not in YLHG, NH₄⁺ was taken up by the cells during sporulation. The total amount of nitrogen used by the bacteria in YLLG was less than that used by the bacteria in YLHG, although a significant amount of NH₄⁺ was present in the medium throughout sporulation. Despite these differences, growth and temporal expression of key sigma factors involved in sporulation were parallel, indicating that the genetic time frames of sporulation were similar under both conditions. Nevertheless, in YLHG, dipicolinic acid production started later and the spores were released from the mother cells much later than in YLLG. Notably, spores had a higher heat resistance when obtained after growth in YLHG than when obtained after growth in YLLG, and the spores germinated more rapidly and completely in response to inosine, L-alanine, and a combination of these two germinants.

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* Corresponding author. Mailing address: Bornsesteeg 59, P.O. Box 17, 6700 AA Wageningen, The Netherlands. Phone: 31-317-475109. Fax: 31-317-475347. E-mail: Ynte.deVries{at}wur.nl.

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Applied and Environmental Microbiology, June 2005, p. 3248-3254, Vol. 71, No. 6
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.6.3248-3254.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

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• Hornstra, L. M., de Vries, Y. P., de Vos, W. M., Abee, T. (2006). Influence of Sporulation Medium Composition on Transcription of ger Operons and the Germination Response of Spores of Bacillus cereus ATCC 14579.. Appl. Environ. Microbiol. 72: 3746-3749 [Abstract] [Full Text]