Growth-related variations in the Bacillus cereus secretome.
Using 2-DE, transcriptional gene fusions and cell cytotoxicity assays, we followed changes in the Bacillus cereus strain ATCC14579 secretome, gene expression and culture supernatant cytotoxicity from the end of the vegetative phase up to 5 h after entry into the stationary phase. The concentration of each of the 22 proteins in the culture supernatant was determined at various times. In addition, the stability of the proteins was studied. Fifteen of these proteins, including 14 members of the virulence regulon PlcR, were known or predicted to be secreted. All of the secreted proteins reached a maximum concentration during early stationary phase, but there were significant differences in the kinetics of their concentrations. The time courses of protein concentrations were in agreement with gene expression data, except for cytotoxin CytK, which was unstable, and for the metalloprotease InhA1. Supernatant cytoxicity also peaked in early stationary phase, and the kinetics of cytotoxicity paralleled the time course of concentration of the PlcR-controlled toxin, CytK. Our concomitant study of the time course of protein concentrations, gene expression and supernatant cytotoxicity reveals that the pathogenic potential of B. cereus peaks during the transition state. It also suggests that there is diversity in the regulation of gene expression within the PlcR regulon.
Gilois
Nathalie
N
Institut National de la Recherche Agronomique (INRA), Génétique microbienne et Environnement, Guyancourt, France.
Ramarao
Nalini
N
Bouillaut
Laurent
L
Perchat
Stéphane
S
Aymerich
Stéphane
S
Nielsen-Leroux
Christina
C
Lereclus
Didier
D
Gohar
Michel
M
D001409:Bacillus cereus / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology*; D001426:Bacterial Proteins / Q000032:analysis* / Q000235:genetics; D015180:Electrophoresis, Gel, Two-Dimensional; D005089:Exocytosis; D015870:Gene Expression; D008969:Molecular Sequence Data; D013997:Time Factors
D001426:Bacterial Proteins