Sequence analysis of three Bacillus cereus loci carrying PlcR-regulated genes encoding degradative enzymes and enterotoxin

Biotechnology Centre of Oslo and School of Pharmacy, University of Oslo, PO Box 1123, N-0349 Oslo, Norway 1 Unité de Biochimie Microbienne, Centre National de la Recherche Scientifique URA 1300, Institut Pasteur, Paris, France 2 Unité de Biochimie Physiologique, Université Catholique de Louvain, Louvain-la-Neuve, Belgium 3 Institut für Mikrobiologie, J. W. Göethe Universität, Frankfurt, Germany 4 Unité de Lutte Biologique, Institut National de la Recherche Agronomique, France 5 Author for correspondence: Anne-Brit Kolstø. Tel: +47 22 95 84 60. Fax: +47 22 69 41 30. e-mail: annebko{at}biotek.uio.no PlcR is a pleiotropic regulator of extracellular virulence factors in the opportunistic human pathogen Bacillus cereus and the entomopathogenic Bacillus thuringiensis , and is induced in cells entering stationary phase. Among the genes regulated by PlcR are: plcA , encoding phosphatidylinositol-specific phospholipase C (PI-PLC); plc , encoding phosphatidylcholine-preferring phospholipase C (PC-PLC); nhe , encoding the non-haemolytic enterotoxin; hbl , encoding haemolytic enterotoxin BL (HBL); and genes specifying a putativeS-layer like surface protein and a putative extracellular RNase. By analysing 37·1 kb of DNA sequence surrounding hbl , plcA and plcR , 28 ORFs were predicted. Three novel genes putatively regulated by PlcR and encoding a neutral protease (NprB), a subtilase family serine protease (Sfp) and a putative cell-wall hydrolase (Cwh) were identified. The corresponding sfp and cwh genes were located in the immediate upstream region of plcA and could both be regulated by a putative PlcR-binding site positioned between the inversely transcribed genes. Similarly, nprB was positioned directly upstream and transcribed in the opposite orientation to plcR . Genes surrounding plcA , plcR and hblCDAB that were lacking an upstream PlcR regulatory sequence did not appear to serve functions apparently related to PlcR and did not exhibit a conserved organization in Bacillus subtilis . View this table: [in this window] [in a new window] Table 1. Genes surrounding the hbl , plcR and plcA loci Keywords: PlcR regulator, HBL enterotoxin, virulence, Bacillus cereus Abbreviations: PC-PLC, phosphatidylcholine-preferring phospholipase C; PI-PLC, phosphatidylinositol-specific phospholipase C The EMBL accession numbers for the sequences reported in this paper are given in Table 1.