GSE61334
Defining the regulon of a CzcRS-like two-component system in Burkholderia cenocepacia K56-2 (ChIP-Seq)
BACKGROUND: We identified that a putative CzcRS-like two-component system (TCS) in Burkholderia cenocepacia K56-2 is required for heavy metal resistance and virulence. In an attempt to identify genes directly regulated by the CzcR response regulator, we performed ChIP-seq analysis to identify genomic regions bound by CzcR. METHODS. Sequence encoding a FLAG octapeptide (Sigma-Aldrich) was introduced to the 3’ end of the czcR gene at its native chromosomal position in wild-type B. cenocepacia K56-2. Wildtype K56-2 and the CzcR-FLAG strain were grown in 50 ml tryptone soya broth (TSB) in the presence or absence of 1.5 mM zinc chloride. After overnight incubation, anti-FLAG immunoprecipitation of CzcR-bound genomic DNA was performed. Wildtype K56-2 was processed in parallel, to serve as a control against which to assess for enrichment of genomic regions. Illumina sequencing libraries were prepared from the resulting DNA using the Nextflex ChIPseq protocol (Bioo Scientific) with indexed adapters. Libraries were amplified by 18 cycles PCR, purified using 0.8 volumes Ampure XP beads (Beckman Coulter) and quantified with a Bioanalyzer 7500 assay (Agilent). Libraries ranged in size from 150 bp to 800 bp with a average insert size of 310 bp. Libraries were pooled in equimolar concentrations, denatured and diluted to 6.5 pM, clustered  on a flowcell using a cBOT (Illumina) and sequenced on a HiSeq2000 (Illumina). Paired-end reads were filtered using the fastq-mcf package from the ea-utils suite to remove reads with less than 90% Q20 scores or above and to trim off adaptor sequence. The reads were then aligned against the B. cenocepacia J2315 genome (NC_011001-NC_011003) using BWA (0.5.9) and converted to BAM format using Samtools. Potential PCR duplicates were removed using the samtools rmdup command.  The MACS package (v1.4) was used to compare and contrast the control and sample data using the –call-subpeaks and –w options. RESULTS: Relative to wildtype B. cenocepacia K56-2, the only genomic region that was found to be enriched by the ChIP-seq analysis of the CzcR-FLAG strain mapped to nucleotide coordinates 787809-798988 on chromosome 2. This region includes the czcRS genes and those encoding the associated efflux pump (CzcCBA). Overall design: Genomic regions bound by the CzcR response regulator were identified by ChIP-seq analysis of a strain expressing a FLAG-tagged CzcR protein. Enriched genomic regions were determined by comparison to the wildtype (parental) strain which did not possess a FLAG tag. Sequencing was performed on an Illumina HiSeq2000.