Catabolite Regulation of the Bacillus subtilis ctaBCDEF Gene Cluster

Abstract

Bacillus subtilis cytochrome c oxidase caa 3 is encoded by the ctaCDEF genes at the ctaABCDEF locus, with the ctaBCDEF genes organized as an operon-like unit. A dyad symmetry sequence and a catabolite response element homolog can be recognized in the 240-bp intercistronic region between ctaB and ctaC. ctaB-lacZ and ctaBCD-lacZ transcriptional fusions integrated at the native locus were used to study catabolite effects on transcription of the ctaB and ctaCDEF genes. In Schaeffer's medium lacking glucose, ctaBCD-lacZ was expressed at a very low level during the exponential phase, and expression increased about 30-fold 2 h after entry into the stationary phase. In the presence of 0.5% glucose, ctaBCD-lacZ expression was totally repressed. In contrast to ctaBCD-lacZ, ctaB-lacZ was constitutively expressed regardless of carbon source. The ctaCDEF genes were separated from ctaB by insertion of plasmids carrying selectable markers in such a way that the ctaCDEF and ctaB transcription units remained intact. Enzymatic assays of caa 3 with these constructs, showed that ctaCDEF was not expressed independently of ctaB. Also, when a ctaB-ctaC-lacZ fusion (containing the ctaB-ctaC intercistronic region) was placed at a remote nonessential locus, ␤-galactosidase activity could not be detected. The absence of a promoter in the ctaB-ctaC intercistronic space also was indicated by the inability to detect ctaC-specific transcripts with RNase protection assays, primer extension, and rapid amplification of 5 cDNA ends. Direct mRNA measurements showed that, in the presence of 0.5% glucose, ctaBCDEF transcripts terminated at the 3 end of the putative stem-loop structure and the distal portion was down-regulated. A possible mechanism for ctaCDEF gene regulation is suggested. Catabolite repression of ctaBCD-lacZ was partly dependent on CcpA but was independent of HPr. The expression of ctaBCDEF also appears to require the strC, ctaA, and resD-resE gene products.

ResDE Two-Component Regulatory System Mediates Oxygen Limitation-Induced Biofilm Formation by Bacillus amyloliquefaciens SQR9

“…Our previous work showed that the ResDE two-component regulatory system regulates biofilm formation in B. amyloliquefaciens SQR9 (39), but the triggering environmental signal and the downstream molecular pathway remained unclear. Many studies have revealed the regulatory role of ResDE in both aerobic and anaerobic respiration in bacteria (40)(41)(42)(43)(44). Upon sensing a decrease in oxygen pressure, ResE activity changes from that of a phosphatase to a kinase, and it then transfers a phosphoryl group to the response regulator ResD; ResDϳP improves the transcription of targeted genes involved in the synthesis of heme-containing components of the electron transport chain (45).…”

Estimation of P-to-O ratio inBacillus subtilis and its influence on maximum riboflavin yield

“…The main electron flow in glucose-grown B. subtilis is via the aa 3 oxidase (Santana et al, 1992) while the bd oxidase appears to be relevant mainly at low oxygen tension (Winstedt et al, 1998). The cytochrome c branch, which also contains the energy-coupling menaquinone:cytochrome c oxidoreductase (bc complex), is subject to catabolite repression and therefore undetectable in glucose-grown B. subtilis, but is expressed during growth on nonfermentable carbon sources (Liu and Taber, 1998;Yu et al, 1995). Thus, in glucose-grown B. subtilis, the maximum P/O appears to be 1 1 ⁄3, a value that compares very well with the overall respiratory H + /e − stoichiometry of 1.9 determined from oxygen pulse experiments with exponentially growing B. subtilis (Lauraeus and Wikström, 1993).…”

“…A conceptually simpler strategy would involve deleting the bd oxidases. Potentially adverse kinetic (Liu and Taber, 1998;Santana et al, 1992;Winstedt et al, 1998;Yu et al, 1995) and genomic database information (Kunst et al, 1997). The stoichiometry of energy coupling was estimated from the reported mechanisms of proton translocation (Trumpower and Gennis, 1994).…”

TheBacillus subtilis ctaBparalogue,yjdK, can complement the heme A synthesis deficiency of a CtaB-deficient mutant

“…The ctaA and ctaB genes are required for heme A synthesis in B. subtilis [1,2]. These genes are located at 133° on the chromosome, immediately upstream of the ctaCDEFG gene cluster and ctaB is co‐transcribed with ctaCDEF [3].…”