The Transcriptional Regulator BpsR Controls the Growth of Bordetella bronchiseptica by Repressing Genes Involved in Nicotinic Acid Degradation

Abstract

Many of the pathogenic species of the genus have an absolute requirement for nicotinic acid (NA) for laboratory growth. These Gram-negative bacteria also harbor a gene cluster homologous to the cluster of which is involved in the aerobic degradation of NA and its transcriptional control. We report here that BpsR, a negative regulator of biofilm formation and Bps polysaccharide production, controls the growth of by repressing the expression of genes. The severe growth defect of the Δ strain in Stainer-Scholte medium was restored by supplementation with NA, which also functioned as an inducer of genes at low micromolar concentrations that are usually present in animals and humans. Purified BpsR protein bound to the promoter region, and its DNA binding activity was inhibited by 6-hydroxynicotinic acid (6-HNA), the first metabolite of the NA degradative pathway. Reporter assays with the isogenic mutant derivative of the wild-type (WT) strain harboring deletion in , which encodes a putative nicotinic acid hydroxylase responsible for conversion of NA to 6-HNA, showed that 6-HNA is the actual inducer of the genes in the bacterial cell. Gene expression profiling further showed that BpsR dually activated and repressed the expression of genes associated with pathogenesis, transcriptional regulation, metabolism, and other cellular processes. We discuss the implications of these findings with respect to the selection of pyridines such as NA and quinolinic acid for optimum bacterial growth depending on the ecological niche. BpsR, the previously described regulator of biofilm formation and Bps polysaccharide production, controls growth by regulating the expression of genes involved in the degradation of nicotinic acid (NA). 6-Hydroxynicotinic acid (6-HNA), the first metabolite of the NA degradation pathway prevented BpsR from binding to DNA and was the actual inducer. We hypothesize that BpsR enables bacteria to efficiently and selectively utilize NA for their survival depending on the environment in which they reside. The results reported herein lay the foundation for future investigations of how BpsR and the alteration of its activity by NA orchestrate the control of growth, metabolism, biofilm formation, and pathogenesis.

Regulatory Mechanism of Nicotine Degradation in Pseudomonas putida

“…Many studies have reported that the intermediates are able to inhibit the repressors, responsible for the corresponding gene cluster(s). For example, in the nicotine acid degradation pathway, which overlaps in part with nicotine degradation along the pyrrolidine pathway, NiaR and BpsR can be inhibited by nicotine acid or its intermediate (18, 19). However, in this study, HSP could only prevent the NicR2 to bind to the promoters, which is different from the reported repressors in nicotine acid degradation.…”

Structural mechanism for regulation of DNA binding of BpsR, a Bordetella regulator of biofilm formation, by 6-hydroxynicotinic acid

“…Additionally, BpsR regulates a number of genes relating to cell adhesion, cell motility, cell wall strength, and intra- and extracellular transport [15,16]. Recently, we and others have shown that BpsR controls the growth of B .…”

“…Recently, we and others have shown that BpsR controls the growth of B . bronchiseptica by repressing genes involved in nicotinic acid (NA) degradation [16,17]. Nicotinic acid or nicotinamide is essential for the growth of many pathogenic Bordetella species in the laboratory.…”

“…pertussis , and B . parapertussis [16,17] with a similar pathway conserved in other bacteria [18,19]. In the first step of degradation, NA is oxidized to 6-hydroxynicotinic acid (6HNA) by the nicA and nicB gene products [18,19].…”

“…In the first step of degradation, NA is oxidized to 6-hydroxynicotinic acid (6HNA) by the nicA and nicB gene products [18,19]. BpsR represses expression of the downstream nicC and nicE genes [16]. BpsR repression is relieved by binding of 6-hydroxynicotinic acid (6HNA), allowing tight regulation of the pathway to control NA metabolism according to the needs and environment of the bacterium.…”