Disease relevance of sigB

• Mutation of sigB impairs the ability of Listeria monocytogenes to grow in sublethal levels, and to survive in lethal concentrations, of the bacteriocins nisin and lacticin 3147 and the antibiotics ampicillin and penicillin G [1].
• In the studies presented here, we have cloned the sigB gene and several rsb genes from L. monocytogenes, encoding homologs of the alternative sigma factor sigmaB and the RsbUVWX proteins, which govern transcription of a general stress regulon in the related bacterium Bacillus subtilis [2].
• Comparative genomic analysis of the sigB operon in Listeria monocytogenes and in other Gram-positive bacteria [3].

High impact information on sigB

• The operon, herein designated bilE (bile Exclusion) is preceded by consensus sigmaA- and sigmaB-dependent promoter-binding sites and is transcriptionally upregulated at elevated osmolarities and reduced temperatures (stresses known to induce sigB) [4].
• In addition to being incapable of bile hydrolysis, a sigB mutant was shown to be exquisitely sensitive to bile salts [5].
• We demonstrate that prfAp(2) is a functional sigma(B)-dependent promoter and that a sigB deletion mutation affects the virulence phenotype of L. monocytogenes [6].
• These findings highlight the importance of complementing phenotypic characterizations with gene expression studies to identify direct and indirect effects of null mutations in regulatory genes, such as sigB [7].
• The transcription of betL was found to be sigB independent [8].

Chemical compound and disease context of sigB

• To determine the contribution of sigma B (sigma(B)) to survival of stationary-phase Listeria monocytogenes cells following exposure to environmental stresses, we compared the viability of strain 10403S with that of an isogenic nonpolar sigB null mutant strain after exposure to heat (50 degrees C), ethanol (16.5%), or acid (pH 2.5) [9].

Biological context of sigB

• The alternative sigma factor sigma(B), encoded by sigB, is responsible for regulating transcription of several L. monocytogenes virulence and stress-response genes, including genes that contribute to establishment of gastrointestinal infections [10].
• Growth kinetics of stationary phase wild-type and sigB mutant cells were compared, without prechilling and after prechilling at 4 degrees C. The two serotypes had similar survival capabilities under the conditions examined, and the sigB gene was influential in survival of chill stress, but was dependent upon additional nutritional factors [11].

Anatomical context of sigB

• The sigB mutant was further characterized in mouse models of listeriosis by determining recovery rates of the wild-type and mutant strains from livers and spleens following intragastric or intraperitoneal infection [12].

Associations of sigB with chemical compounds

• Analysis of the cytoplasmic pools of compatible solutes during balanced growth revealed that both carnitine and betaine steady-state pools were reduced in the sigB mutant [8].
• A null mutation in the sigB gene led to substantial defects in the ability of L. monocytogenes to use betaine and carnitine as osmoprotectants [2].
• The L. monocytogenes and B. subtilis sigB and rsb genes are similar in sequence and physical organization; however, we observed that the activity of sigmaB in L. monocytogenes was uniquely responsive to osmotic upshifting, temperature downshifting, and the presence of EDTA in the growth medium [2].
• Null mutations were generated in the sigB genes of L. monocytogenes L61 (serotype 1/2a) and L99 (serotype 4c), and the survival of the resulting mutants was compared with that of the wild-type strains under osmotic, oxidative, and carbon starvation stress conditions and on exposure to bacteriocins, ethanol, acid, and heat [13].

Analytical, diagnostic and therapeutic context of sigB

• We selected 157 Listeria isolates to evaluate a combination of a previously described multiplex PCR assay and sigB allelic typing as an alternative molecular serotyping and subtyping strategy for L. monocytogenes [14].

References