Transcriptomics Analysis Uncovers Transient Ceftazidime Tolerance in Burkholderia Biofilms

Abstract

Burkholderia pseudomallei is an etiological agent of melioidosis, a severe community-acquired infectious disease. B. pseudomallei strain K96243 is sensitive to the drug ceftazidime (CAZ), but has been shown to exhibit transient CAZ tolerance when in a biofilm form. To investigate an observed shift in gene expression profile during CAZ tolerance condition and to better understand the mechanistic aspects of this transient tolerance, RNA-sequencing was performed on B. pseudomallei K96243 from the following three states: planktonic, biofilm, and planktonic shedding. Results indicated that the expression of 651 genes (10.97%) were significantly changed in both biofilm (resistant) and planktonic shedding (sensitive) cells in comparison to the planktonic state. The top four highly expressed genes identified in both states are associated with nitrosative stress response (BPSL2368), Fe–S homeostasis (BPSL2369), and nitrate respiration (BPSS1154 and BPSS1158). Additionally, five orthologous genes, BPSL2370–BPSL2374, implicated in Fe–S cluster biogenesis, and another gene, BPSL2863, involved in DNA-binding of the stress protein ferritin, were shown to increase expression by RT-qPCR. The shift in gene expression was especially prominent at the late stages of biofilm growth (72 and 96 h), specifically in the biofilm-challenged CAZ survivor cells. This suggested that in response to stress in a biofilm, differential expression of these genes may support development of the CAZ tolerance in Burkholderia. The application of iron chelator deferoxamine (DFO) to the biofilm caused a significant reduction in biofilm formation and associated CAZ tolerance. Therefore, the shift in Fe–S metabolism when B. pseudomallei is in a biofilm may help stabilize the levels of reactive oxygen species (ROS), thereby limiting tolerance to CAZ.

Nanotechnology-Based Drug Delivery Systems to Control Bacterial-Biofilm-Associated Lung Infections

“…In contrast to their planktonic counterparts, bacteria within the biofilm can express specific genes that enhance bacteria tolerance [11]. For instance, Burkholderia pseudomallei, responsible for melioidosis, has been reported to tolerance to ceftazidime (CAZ) in its biofilm state, while remaining sensitive in its planktonic state [100]. RNA-sequencing studies of this bacterium across planktonic, biofilm, and planktonic shedding states revealed that approximately 10% of gene expression changed in both biofilm and planktonic shedding compared to planktonic bacteria.…”

Black Carbon Impacts on Paraburkholderia xenovorans Strain LB400 Cell Enrichment and Activity: Implications toward Lower-Chlorinated Polychlorinated Biphenyls Biodegradation Potential

“…A variety of aerobes can degrade PCBs, − but Paraburkholderia xenovorans strain LB400 demonstrates higher degradation efficacy for wide ranges of PCBs (mono- to hexa-chlorinated biphenyls). ,− PCB oxidation proceeds via the bph pathway; thus, bphA is commonly used as a biomarker because it encodes biphenyl dioxygenase, the initial catabolic enzyme in the pathway. ,, Specific carbon/energy sources (e.g., biphenyl, benzoate) are required for bph pathway induction, and many PCB congeners with 6 chlorines or less are cometabolized in the presence of biphenyl or benzoate. ,− Bioaugmenting sediments with suspended LB400 cells can efficiently oxidize LC-PCB congeners (up to trichlorinated homologues) and mitigate flux to the air. , Nevertheless, free cells often demonstrate unsatisfactory survivability and activity due to environmental fluctuations and nutrient availability − factors that can be moderated when cells exist as biofilms. Biofilms display increased gene expression levels and produce exopolysaccharides that improve stress tolerance and cell removal resistance. ,− Multiple studies have examined immobilized anaerobes that dechlorinate PCBs, ,− but comparatively few have focused on removing LC-PCBs through bioaugmentation of immobilized PCB-degrading aerobes to mitigate the direct human exposure pathway. − Improved LC-PCB bioremediation strategies require an enhanced understanding of immobilized PCB-degrading cells and how cells interact with surface materials.…”