title: Analysis of acid-stressed Bacillus cereus reveals a major oxidative response and inactivation-associated radical formation.
abstract: 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.
authors.affiliation: Top Institute Food and Nutrition, Wageningen, the Netherlands. maarten.mols@wur.nl
authors.forename: Maarten
authors.initials: M
authors.lastname: Mols
authors.forename: Richard
authors.initials: R
authors.lastname: van Kranenburg
authors.forename: Clint C J
authors.initials: CC
authors.lastname: van Melis
authors.forename: Roy
authors.initials: R
authors.lastname: Moezelaar
authors.forename: Tjakko
authors.initials: T
authors.lastname: Abee
mesh_terms: D000143:Acids / Q000494:pharmacology*; D001409:Bacillus cereus / Q000254:growth & development* / Q000378:metabolism; D002374:Catalase / Q000378:metabolism; D016000:Cluster Analysis; D005609:Free Radicals / Q000378:metabolism; D020869:Gene Expression Profiling; D006863:Hydrogen-Ion Concentration; D050296:Microbial Viability; D020411:Oligonucleotide Array Sequence Analysis; D018384:Oxidative Stress; D010641:Phenotype; D012329:RNA, Bacterial / Q000032:analysis; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D000143:Acids; D005609:Free Radicals; D012329:RNA, Bacterial; D002374:Catalase; D013482:Superoxide Dismutase