An Extracytoplasmic-Function Sigma Factor Is Involved in a Pathway Controlling β-Exotoxin I Production in Bacillus thuringiensis subsp. thuringiensis Strain 407-1

摘要: β-Exotoxin I is an insecticidal nucleotide analogue secreted by various Bacillus thuringiensis strains. In this report, we describe the characterization and transcriptional analysis of a gene cluster, designated sigW-ecfX-ecfY, that essential for β-exotoxin production in B. subsp. strain 407-1. strain, disruption sigW cluster resulted nontoxic culture supernatants. encodes protein 177 residues 97 94% identical to two putative RNA polymerase extracytoplasmic-function-type sigma factors from anthracis Ames cereus ATCC 14579, respectively. It also 50, 30, 26% SigW Clostridium perfringens SigX subtilis, EcfX, encoded following sigW, significantly repressed expression when both genes were overtranscribed, suggesting it could be anti-sigma factor SigW. Following loss its curable cry plasmid, 407 became unable synthesize crystal toxins, contrast mutant 407-1(Cry−)(Pig+), which overproduced molecule absence plasmid. Transcriptional indicated was expressed during stationary phase only 407-1(Cry−)(Pig+) mutant. This suggests wild type-407(Cry+) produced determinants located on gene-bearing plasmid able induce plasmids. Although signal responsible activation unknown, these results indicate can restored or induced via alternative pathway requires expression.