Expression of canonical SOS genes is not under LexA repression in Bdellovibrio bacteriovorus.
The here-reported identification of the LexA-binding sequence of Bdellovibrio bacteriovorus, a bacterial predator belonging to the delta-Proteobacteria, has made possible a detailed study of its LexA regulatory network. Surprisingly, only the lexA gene and a multiple gene cassette including dinP and dnaE homologues are regulated by the LexA protein in this bacterium. In vivo expression analyses have confirmed that this gene cassette indeed forms a polycistronic unit that, like the lexA gene, is DNA damage inducible in B. bacteriovorus. Conversely, genes such as recA, uvrA, ruvCAB, and ssb, which constitute the canonical core of the Proteobacteria SOS system, are not repressed by the LexA protein in this organism, hinting at a persistent selective pressure to maintain both the lexA gene and its regulation on the reported multiple gene cassette. In turn, in vitro experiments show that the B. bacteriovorus LexA-binding sequence is not recognized by other delta-Proteobacteria LexA proteins but binds to the cyanobacterial LexA repressor. This places B. bacteriovorus LexA at the base of the delta-Proteobacteria LexA family, revealing a high degree of conservation in the LexA regulatory sequence prior to the diversification and specialization seen in deeper groups of the Proteobacteria phylum.
Campoy
Susana
S
Centre de Recerca en Sanitat Animal (CReSA), 08193 Bellaterra, Spain.
Salvador
Noelia
N
Cortés
Pilar
P
Erill
Ivan
I
Barbé
Jordi
J
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D001501:Bdellovibrio / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D011485:Protein Binding; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D013014:SOS Response, Genetics / Q000235:genetics*; D012697:Serine Endopeptidases / Q000235:genetics* / Q000378:metabolism; D000099160:LexA Repressor Protein
D001426:Bacterial Proteins; D012097:Repressor Proteins; D012697:Serine Endopeptidases; D000099160:LexA Repressor Protein