Response of Bacillus cereus ATCC 14579 to challenges with sublethal concentrations of enterocin AS-48.
BACKGROUND
Enterocin AS-48 is produced by Enterococcus faecalis S48 to compete with other bacteria in their environment. Due to its activity against various Gram positive and some Gram negative bacteria it has clear potential for use as a food preservative. Here, we studied the effect of enterocin AS-48 challenges on vegetative cells of Bacillus cereus ATCC 14579 by use of transcriptome analysis.


RESULTS
Of the 5200 genes analysed, expression of 24 genes was found to change significantly after a 30 min treatment with a subinhibitory bacteriocin concentration of 0.5 microg/ml. Most of up-regulated genes encode membrane-associated or secreted proteins with putative transmembrane segments or signal sequences, respectively. One operon involved in arginine metabolism was significantly downregulated. The BC4206-BC4207 operon was found to be the most upregulated target in our experiments. BC4206 codes for a PadR type transcriptional regulator, while BC4207 codes for a hypothetical membrane protein. The operon structure and genes are conserved in B. cereus and B. thuringiensis species, but are not present in B. anthracis and B. subtilis. Using real-time qPCR, we show that these genes are upregulated when we treated the cells with AS-48, but not upon nisin treatment. Upon overexpression of BC4207 in B. cereus, we observed an increased resistance against AS-48. Expression of BC4207 in B. subtilis 168, which lacks this operon also showed increased resistance against AS-48.


CONCLUSIONS
BC4207 membrane protein is involved in the resistance mechanism of B. cereus cells against AS-48.
Grande Burgos
María J
MJ
Departamento de Ciencias de Salud (Area de Microbiología), Facultad de Ciencias Experimentales, Universidad de Jaén, 23071-Jaén, Spain. mjgrandeb@yahoo.es
Kovács
Akos T
AT
Mirończuk
Aleksandra M
AM
Abriouel
Hikmate
H
Gálvez
Antonio
A
Kuipers
Oscar P
OP
D001409:Bacillus cereus / Q000187:drug effects / Q000235:genetics*; D001414:Bacitracin / Q000494:pharmacology; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics*; D001430:Bacteriocins / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000235:genetics; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D008826:Microbial Sensitivity Tests; D009561:Nisin / Q000494:pharmacology; D020411:Oligonucleotide Array Sequence Analysis; D009876:Operon
D001425:Bacterial Outer Membrane Proteins; D001430:Bacteriocins; D004269:DNA, Bacterial; C466236:enterocin AS-48, Enterococcus faecalis; D001414:Bacitracin; D009561:Nisin