Abh and AbrB Control of Bacillus subtilis Antimicrobial Gene Expression

Abstract

The Bacillus subtilis abh gene encodes a protein whose N-terminal domain has 74% identity to the DNAbinding domain of the global regulatory protein AbrB. Strains with a mutation in abh showed alterations in the production of antimicrobial compounds directed against some other Bacillus species and gram-positive microbes. Relative to its wild-type parental strain, the abh mutant was found deficient, enhanced, or unaffected for the production of antimicrobial activity. Using lacZ fusions, we examined the effects of abh upon the expression of 10 promoters known to be regulated by AbrB, including five that transcribe well-characterized antimicrobial functions (SdpC, SkfA, TasA, sublancin, and subtilosin). For an otherwise wild-type background, the results show that Abh plays a negative regulatory role in the expression of four of the promoters, a positive role for the expression of three, and no apparent regulatory role in the expression of the other three promoters. Binding of AbrB and Abh to the promoter regions was examined using DNase I footprinting, and the results revealed significant differences. The transcription of abh is not autoregulated, but it is subject to a degree of AbrB-afforded negative regulation. The results indicate that Abh is part of the complex interconnected regulatory system that controls gene expression during the transition from active growth to stationary phase.Upon entry into stationary phase and sporulation, strains of Bacillus subtilis cells produce different spectrums of various antibiotic and antimicrobial functions (36). Among the antimicrobials produced by B. subtilis 168 strains are sublancin (27), subtilosin A (2, 35), bacilysocin (46), bacilysin (20,22,48), the SdpC sporulation delay toxin (8,14), the SkfA sporulation killing factor (1, 14), and the TasA protein (37). The pleiotropic AbrB protein is known to play a role in regulating most of these antimicrobials in addition to numerous other genes expressed by postexponential-phase cells (22,31,36,37,54).The examination of over 60 chromosomal sites of AbrB binding has failed to uncover a consensus base sequence that has substantive predictive value and that can adequately explain target selection and affinity. High-affinity sites of AbrB-DNA interactions selected using in vitro methods do show convergence to a consensus, but sequences resembling this consensus are rarely found in the chromosomal sites (50, 53). It has been hypothesized that AbrB achieves binding specificity by recognizing three-dimensional DNA architectures that are shared by a finite subset of base sequences (5,40,42,45,53). A major factor accounting for what has been termed the "limited promiscuity" of AbrB-DNA interactions is believed to be the dynamic flexibility in the DNA-binding domain of the protein; this flexibility allows it to conform to different targets with thermodynamically favorable contacts (4, 6, 47).B. subtilis contains two AbrB paralogs: Abh (6, 23) andSpoVT (3). The abh gene codes for a protein of 92 amino acids, showing 58% overall identity...

Cannibalism stress response in Bacillus subtilis

“…SboA (subtilosin A) is another bacteriocin produced by B. subtilis W168. Although it is known to be transcriptionally regulated by AbrB and by the two-component regulatory proteins ResDE (Nakano et al, 2000;Strauch et al, 2007), it has been reported to be produced only under anaerobic growth conditions (Nakano et al, 2000). Indeed, we found the sboA promoter to be inactive over the whole time course under our cultivation conditions (data not shown).…”

“…The first AMP we considered was SunA (sublancin 168), which is an SPb prophage-derived bacteriocin described as an S-linked glycopeptide active against Gram-positive bacteria (Oman et al, 2011). Its production is known to be repressed during the exponential growth phase by the transcriptional regulators AbrB and Rok (Albano et al, 2005;Strauch et al, 2007). Another peptide that might trigger stationary-phase induction of the CESR is the YydF peptide, which has been shown to be an endogenous inducer of the LiaRS system Wolf et al, 2010).…”

Global Transcriptional Control by NsrR in Bacillus subtilis

“…NsrR participates in transcriptional control of genes repressed by both AbrB and Rok. Previous studies showed that genes involved in cell surface and extracellular functions such as sdpA, sboA (for subtilosin A) (65), and yydH (for an ABC transporter) are repressed by both AbrB and Rok (Table 1) (3,55). AbrB is a transition state regulator involved in controlling postexponential processes in B. subtilis (56,58), and Rok was originally identified as a negative regulator of comK that encodes a transcription factor required for competence development (28).…”

“…In addition, sdpA-1, sdpA-2, and sboA-2 sequences in shown Fig. S6 reside within regions where AbrB was shown to bind by DNase I footprinting (55). Genome-wide binding profiles of AbrB revealed that three out of four binding patterns contain TGGNA motifs connected by AϩT-rich sequence (11).…”

Isolation of a Variant of Subtilosin A with Hemolytic Activity

“…In addition, the transition state regulator AbrB represses sboA-alb transcription independently from the ResD-ResE pathway (20). DNase I footprinting analysis showed that AbrB binds the sboA regulatory region (from position Ϫ100 to Ϫ39 relative to the transcription start site) (28). Furthermore, Rok, which is known to be a regulator of competence development, represses sboA-alb transcription (1).…”