Get access

Analysis of acid-stressed Bacillus cereus reveals a major oxidative response and inactivation-associated radical formation

Authors

  • Maarten Mols,

    Corresponding author
    1. Top Institute Food and Nutrition, Wageningen, the Netherlands.
    2. Laboratory of Food Microbiology, Wageningen University, Wageningen, the Netherlands.
    Search for more papers by this author
  • Richard Van Kranenburg,

    1. Top Institute Food and Nutrition, Wageningen, the Netherlands.
    2. PURAC, Gorinchem, the Netherlands.
    Search for more papers by this author
  • Clint C. J. Van Melis,

    1. Laboratory of Food Microbiology, Wageningen University, Wageningen, the Netherlands.
    Search for more papers by this author
  • Roy Moezelaar,

    1. Top Institute Food and Nutrition, Wageningen, the Netherlands.
    2. Food Technology Centre, Wageningen University and Research Centre, Wageningen, the Netherlands.
    Search for more papers by this author
  • Tjakko Abee

    1. Top Institute Food and Nutrition, Wageningen, the Netherlands.
    2. Laboratory of Food Microbiology, Wageningen University, Wageningen, the Netherlands.
    Search for more papers by this author

E-mail maarten.mols@wur.nl; Tel. (+31) 317 484983; Fax (+31) 317 484978.

Summary

Acid stress resistance of the food-borne human pathogen Bacillus cereus may contribute to its survival in acidic environments, such as encountered in soil, food and the human gastrointestinal tract. The acid stress responses of B. cereus strains ATCC 14579 and ATCC 10987 were analysed in aerobically grown cultures acidified to pH values ranging from pH 5.4 to pH 4.4 with HCl. Comparative phenotype and transcriptome analyses revealed three acid stress-induced responses in this pH range: growth rate reduction, growth arrest and loss of viability. These physiological responses showed to be associated with metabolic shifts and the induction of general stress response mechanisms with a major oxidative component, including upregulation of catalases and superoxide dismutases. Flow cytometry analysis in combination with the hydroxyl (OH·) and peroxynitrite (ONOO-)-specific fluorescent probe 3′-(p-hydroxyphenyl) fluorescein (HPF) showed excessive radicals to be formed in both B. cereus strains in bactericidal conditions only. Our study shows that radicals can indicate acid-induced malfunctioning of cellular processes that lead to cell death.

Ancillary