Distinct mutations in PlcR explain why some strains of the Bacillus cereus group are nonhemolytic.
Bacillus thuringiensis, Bacillus cereus, and Bacillus anthracis are closely related species belonging to the Bacillus cereus group. B. thuringiensis and B. cereus generally produce extracellular proteins, including phospholipases and hemolysins. Transcription of the genes encoding these factors is controlled by the pleiotropic regulator PlcR. Disruption of plcR in B. cereus and B. thuringiensis drastically reduces the hemolytic, lecithinase, and cytotoxic properties of these organisms. B. anthracis does not produce these proteins due to a nonsense mutation in the plcR gene. We screened 400 B. thuringiensis and B. cereus strains for their hemolytic and lecithinase properties. Eight Hly- Lec- strains were selected and analyzed to determine whether this unusual phenotype was due to a mutation similar to that found in B. anthracis. Sequence analysis of the DNA region including the plcR and papR genes of these strains and genetic complementation of the strains with functional copies of plcR and papR indicated that different types of mutations were responsible for these phenotypes. We also found that the plcR genes of three B. anthracis strains belonging to different phylogenetic groups contained the same nonsense mutation, suggesting that this mutation is a distinctive trait of this species.
Slamti
Leyla
L
Groupe Génétique et Physiologie des Bacillus pathogènes, Institut Pasteur, 75015 Paris, France.
Perchat
Stéphane
S
Gominet
Myriam
M
Vilas-Bôas
Gislayne
G
Fouet
Agnès
A
Mock
Michèle
M
Sanchis
Vincent
V
Chaufaux
Josette
J
Gohar
Michel
M
Lereclus
Didier
D
D000595:Amino Acid Sequence; D001409:Bacillus cereus / Q000235:genetics* / Q000472:pathogenicity; D001426:Bacterial Proteins / Q000235:genetics; D005816:Genetic Complementation Test; D006461:Hemolysis; D008969:Molecular Sequence Data; D009154:Mutation; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics*
D001426:Bacterial Proteins; C466079:PapR protein, Bacillus cereus; C099480:PlcR protein, Bacillus; D015534:Trans-Activators