Burkholderia cenocepacia differential gene expression during host–pathogen interactions and adaptation to the host environment

Abstract

Members of the Burkholderia cepacia complex (Bcc) are important in medical, biotechnological, and agricultural disciplines. These bacteria naturally occur in soil and water environments and have adapted to survive in association with plants and animals including humans. All Bcc species are opportunistic pathogens including Burkholderia cenocepacia that causes infections in cystic fibrosis and chronic granulomatous disease patients. The adaptation of B. cenocepacia to the host environment was assessed in a rat chronic respiratory infection model and compared to that of high cell-density in vitro grown cultures using transcriptomics. The distribution of genes differentially expressed on chromosomes 1, 2, and 3 was relatively proportional to the size of each genomic element, whereas the proportion of plasmid-encoded genes differentially expressed was much higher relative to its size and most genes were induced in vivo. The majority of genes encoding known virulence factors, components of types II and III secretion systems and chromosome 2-encoded type IV secretion system were similarly expressed between in vitro and in vivo environments. Lower expression in vivo was detected for genes encoding N-acyl-homoserine lactone synthase CepI, orphan LuxR homolog CepR2, zinc metalloproteases ZmpA and ZmpB, LysR-type transcriptional regulator ShvR, nematocidal protein AidA, and genes associated with flagellar motility, Flp type pilus formation, and type VI secretion. Plasmid-encoded type IV secretion genes were markedly induced in vivo. Additional genes induced in vivo included genes predicted to be involved in osmotic stress adaptation or intracellular survival, metal ion, and nutrient transport, as well as those encoding outer membrane proteins. Genes identified in this study are potentially important for virulence during host–pathogen interactions and may be associated with survival and adaptation to the host environment during chronic lung infections.

TheBurkholderia cenocepaciapeptidoglycan-associated lipoprotein is involved in epithelial cell attachment and elicitation of inflammation

“…We have recently shown that attachment to CF epithelial cells was enhanced over time of chronic colonization in a series of sequential clinical B. cenocepacia isolates (Cullen et al, accepted manuscript); therefore, the observed induction of Pal in the chronic rat infection model complements our findings as it suggests that Pal may contribute to the enhanced host cell attachment observed in the clinical chronic infection isolates and its expression may contribute to successful colonization of the host. The involvement in host cell attachment is also consistent with findings that a lipoprotein, which subsequently showed 95.8% identity to the Pal encoded by BCAL3204, was the immunodominant antigen in Bcc infected mice (Makidon et al, ; O'grady & Sokol, ).…”

“…Pal was among a group of genes that were induced in vivo in a chronic respiratory infection model, suggesting that it contributed to bacterial adaptation and survival in the lungs (O'grady & Sokol, ). We have recently shown that attachment to CF epithelial cells was enhanced over time of chronic colonization in a series of sequential clinical B. cenocepacia isolates (Cullen et al, accepted manuscript); therefore, the observed induction of Pal in the chronic rat infection model complements our findings as it suggests that Pal may contribute to the enhanced host cell attachment observed in the clinical chronic infection isolates and its expression may contribute to successful colonization of the host.…”

An Oxygen-Sensing Two-Component System in the Burkholderia cepacia Complex Regulates Biofilm, Intracellular Invasion, and Pathogenicity

“…Interestingly, homologs of the up-regulated component of the type IVb pilus ( flp subunit) were found to be down-regulated in vivo in a chronic B . cenocepacia infection model in rats [46], suggesting that this pilus is detrimental to in vivo fitness during long-term infections. We also saw that the RNA-binding protein Hfq was upregulated in the fixLJ deletion mutant, suggesting a role for sRNA in modulation of the fix regulon.…”

Gene Expression Profiling of Burkholderia cenocepacia at the Time of Cepacia Syndrome: Loss of Motility as a Marker of Poor Prognosis?

“…Variability in the quantitative PCR results for the QS genes and nonuniformity across the isolates likely reflected a role for QS as a global regulator whose expression is very sensitive to conditions outside the cell (15,18). Nevertheless, the expression of QS genes in isolates from patients A and B matched the microarray data.…”