σ ⁵⁴ -Dependent Response to Nitrogen Limitation and Virulence in Burkholderia cenocepacia Strain H111

Abstract

Members of the genus Burkholderia are versatile bacteria capable of colonizing highly diverse environmental niches. In this study, we investigated the global response of the opportunistic pathogen Burkholderia cenocepacia H111 to nitrogen limitation at the transcript and protein expression levels. In addition to a classical response to nitrogen starvation, including the activation of glutamine synthetase, PII proteins, and the two-component regulatory system NtrBC, B. cenocepacia H111 also upregulated polyhydroxybutyrate (PHB) accumulation and exopolysaccharide (EPS) production in response to nitrogen shortage. A search for consensus sequences in promoter regions of nitrogen-responsive genes identified a 54 consensus sequence. The mapping of the 54 regulon as well as the characterization of a 54 mutant suggests an important role of 54 not only in control of nitrogen metabolism but also in the virulence of this organism.

Regulator LdhR and d -Lactate Dehydrogenase LdhA of Burkholderia multivorans Play Roles in Carbon Overflow and in Planktonic Cellular Aggregate Formation

“…Although the genes encoding the proteins involved in cepacian biosynthesis are well known (5), the regulatory elements controlling the expression of this phenotype remain unknown. The exception is the regulator 54 , which has been shown to positively regulate EPS production in B. cenocepacia grown under nitrogen starvation (30). Here, we have shown a negative effect in EPS biosynthesis by LdhR and LdhA, but this might be a consequence of planktonic cellular aggregate formation.…”

Metabolomics and Transcriptomics Identify Multiple Downstream Targets of Paraburkholderia phymatum σ54 During Symbiosis with Phaseolus vulgaris

“…A genome-wide in-silico search for RpoN DNA binding motifs ( GG CACG-N4-TT GC ) in all P. phymatum promoter sequences was conducted, relying on a previously described position-specific frequency matrix (PSFM) of RpoN binding sites in the closely related strain B. cenocepacia H111 [27]. A total of 409 putative RpoN binding boxes were detected (see Section 3).…”

“…Thus, similar to the situation in α-rhizobia, the alternative RNA polymerase sigma factor RpoN (or σ 54 ) and its enhancer binding protein (EBP) NifA are essential for nitrogenase activity during this β-rhizobial symbiosis. RpoN was originally found to be the key regulator of nitrogen utilization systems in several bacteria [24,25,26,27]. It has since been linked with several phenotypes, including motility [22], exopolysaccharides (EPS) production [27,28], biofilm formation, and other symbiotic and virulence traits [29,30,31].…”

“…RpoN was originally found to be the key regulator of nitrogen utilization systems in several bacteria [24,25,26,27]. It has since been linked with several phenotypes, including motility [22], exopolysaccharides (EPS) production [27,28], biofilm formation, and other symbiotic and virulence traits [29,30,31]. This alternative sigma factor, which requires an EBP to activate gene expression, recognizes and binds consensus sequences located at the −24/−12 positions in the promoter region of target genes [32].…”

Use of Synthetic Hybrid Strains To Determine the Role of Replicon 3 in Virulence of the Burkholderia cepacia Complex

“…Analysis of toxicity from bacterial strains toward C. elegans N2 was performed as previously described (45). Briefly, in a 96-well plate, 20 to 30 L1 larvae of C. elegans N2 were mixed with 80 l of bacterial culture adjusted to an optical density at 600 nm (OD 600 ) of 2.0.…”