Regulation of phenylacetic acid degradation genes of Burkholderia cenocepacia K56-2

Abstract

BackgroundMetabolically versatile soil bacteria Burkholderia cepacia complex (Bcc) have emerged as opportunistic pathogens, especially of cystic fibrosis (CF). Previously, we initiated the characterization of the phenylacetic acid (PA) degradation pathway in B. cenocepacia, a member of the Bcc, and demonstrated the necessity of a functional PA catabolic pathway for full virulence in Caenorhabditis elegans. In this study, we aimed to characterize regulatory elements and nutritional requirements that control the PA catabolic genes in B. cenocepacia K56-2.ResultsTranslational fusions of the PA degradation gene promoters with eGFP were constructed and introduced in B. cenocepacia K56-2. eGFP expression was observed when the reporter strains were grown in minimal media containing glycerol and PA or other compounds expected to proceed through the PA pathway, and in synthetic CF medium (SCFM). Addition of succinate or glucose to the PA containing medium repressed eGFP expression. To show that BCAL0210, a putative TetR-type regulator gene encodes a regulator for the PA genes in B. cenocepacia, we developed a BCAL0210 insertional mutant reporter strain. Results show that these strains exhibit fluorescence regardless of the presence of PA in the culture.ConclusionThe PA catabolic genes of B. cenocepacia K56-2 are induced by PA and other related compounds, are negatively regulated by PaaR (named herein), a TetR-type regulator, and are subjected to catabolic repression by glucose and succinate. As the PA catabolic pathway of B. cenocepacia appears to be induced during growth in synthetic cystic fibrosis medium (SCFM), further research is necessary to determine the relevance of this pathway in CF-like conditions and in other host-pathogen interactions.

Phenylacetyl Coenzyme A Is an Effector Molecule of the TetR Family Transcriptional Repressor PaaR from Thermus thermophilusHB8

“…PaaR probably binds a pseudopalindromic sequence covering the Ϫ10 hexamer of the promoter or transcriptional start site. The consensus sequence is different from those of other TetR family proteins (1,10,23), indicating that the DNA-binding mechanisms differ among the TetR family proteins. The genomic selex experiment isolated large amounts of DNA fragments derived from ORFs, including part of the probable PaaR-binding consensus sequence.…”

Investigation of cytochromes P450 in myxobacteria: Excavation of cytochromes P450 from the genome of Sorangium cellulosum So ce56

“…S1(A)). PA genes are found in pathogenic and nonpathogenic mycobacterial species, actinomycetes, and some proteobacteria [68,69]. Moreover, CYP124E1 in Mycobacterium tuberculosis performed x-hydroxylation of methyl-branched lipids and degradation of the cholesterol [70,71].…”

Phenylacetic Acid Catabolism and Its Transcriptional Regulation in Corynebacterium glutamicum

“…In addition to the PaaR protein from C. glutamicum, two PaaR proteins from T. thermophilus and B. cenocepacia had been identified previously (13,38). By using these functionally characterized PaaR proteins, PaaR orthologs were identified by BLAST searches against the nonredundant set of sequenced bacterial genomes and were used to analyze the phylogenetic relationships between these proteins (Fig.…”

“…First, we collected training sets of prospective target genes for each of 10 defined taxonomic groups possessing PaaR orthologs. These training sets were defined by the analysis of chromosomal colocalizations of paaR genes and information on the known PaaR binding sites from strain AS 1.542 from this study, as well as from T. thermophilus and B. cenocepacia (13,38). Using the motif recognition program applied to each training set of upstream gene regions, we identified conserved PaaR binding motifs, constructed a positional weight matrix for each motif identified, and searched for additional PaaR-binding sites in the genomes analyzed.…”

“…In E. coli and Pseudomonas species, a GntR family transcriptional regulator named PaaX represses the transcription of the paa genes (7,9). In Burkholderia cenocepacia K56-2 and Thermus thermophilus HB8, a transcriptional regulator of the TetR family, named PaaR, has been reported as a repressor of the PAA degradation pathway (13,38). Instead of PAA, PA-CoA acts as the effector for all the regulatory proteins identified so far (9,11,38,48).…”