ScoC regulates peptide transport and sporulation initiation in Bacillus subtilis

Abstract

Oligopeptides are transported into Bacillus subtilis by two ABC transport systems, App and Opp. Transcription of the operon encoding the Opp system was found to occur during exponential growth, whereas the app operon was induced at the onset of stationary phase. Transcription of both operons was completely curtailed by overproduction of the ScoC regulator from a multicopy plasmid and was enhanced in strains with the scoC locus deleted. ScoC, a member of the MarR family of transcription regulators, is known from previous studies to be a negative regulator of sporulation and of protease production that acts by binding directly to the promoters of the genes it regulates. Since peptide transport is essential for inactivation of the negative regulation of sporulation by Rap phosphatases, the control of ScoC transcription repression activity plays a crucial role in the initiation of sporulation.

FIG. 1

(A) Time course of β-galactosidase activity of the opp-lacZ fusion construct (representative of a typical experiment) in the following strains: parental strain JH14279 (□), spo0A12 mutant strain JH14280 (◊), abrB::Tn917 mutant strain JH14282 (●), and spo0A12 abrB::Tn917 mutant strain JH14286 (▵). Time zero is the time of transition from vegetative growth to stationary phase. β-Galactosidase activity in strains harboring lacZ fusion constructs was assayed as previously described (6). Specific activity is expressed in Miller units (17). (B) Time course of β-galactosidase activity of the app-lacZ fusion construct (representative of a typical experiment) in the following strains: parental strain JH14270 (□), spo0A12 mutant strain JH14281 (◊), abrB::Tn917 mutant strain JH14283 (●), and spo0A12 abrB::Tn917 mutant strain JH14285 (▵).

FIG. 2

Effect of scoC deletion on opp (A) or app (B) transcription. Symbols: ○, parental strain JH14279 or JH14270; ■, scoC::cat mutant strain JH14272 or JH14271.

FIG. 3

Effect of scoC overexpression on opp (A) or app (B) transcription. Strain JH14279 (A) or JH14270 (B) carrying replicative plasmid pBS19 (○; vector only), pJM2491 (□); scoC), or pJM2493 (⧫; scoC promoter) was grown in Schaeffer’s sporulation medium containing chloramphenicol at 5 μg/ml. β-Galactosidase activity was measured at the indicated times.

FIG. 4

Time course of β-galactosidase activity of the app-lacZ construct in parental strain JH14270 (□) and sinR mutant strain JH11134 (●).