Project description:Enterobacter cloacae is a Gram-negative nosocomial pathogen of the ESKAPE priority group with increasing multi-drug resistance via the acquisition of resistance plasmids. However, E. cloacae can also display phenotypic antimicrobial resistance, such as heteroresistance or persistence. Here we report that E. cloacae ATCC 13047 and six strains isolated from patients with blood infections display heteroresistance or persistence to aminoglycosides. E. cloacae heteroresistance is transient, accompanied with formation of "petite" colonies and increased MIC against gentamicin and other aminoglycosides used in the clinic, but not other antibiotic classes. To explore the underlying mechanisms, we performed RNA sequencing of heteroresistant bacteria, which revealed global gene-expression changes and a signature of the CpxRA cell envelope stress response. Deletion of the cpxRA two-component system abrogated aminoglycoside heteroresistance and petite colony formation, pointing to its indispensable role in phenotypic resistance. The introduction of a constitutively active allele of cpxA led to high aminoglycoside MICs, consistent with cell envelope stress driving these behaviours in E. cloacae. Cell envelope stress can be caused by environmental cues, including heavy metals. Indeed, bacterial exposure to copper increased gentamicin MIC in the wild type, but not the ΔcpxRA mutant. Moreover, copper exposure also elevated the gentamicin MICs of bloodstream isolates, suggesting that CpxRA- and copper-dependent aminoglycoside resistance is broadly conserved in E. cloacae strains. Altogether, we establish that E. cloacae relies on transcriptional reprogramming via the envelope stress response pathway for transient resistance to a major class of frontline antibiotic.
Project description:Nickel is an essential component of many eukaryotic and prokaryotic metallo-enzymes. Due to its employment in many industrial applications, wastewaters from industrial plants often contain millimolar concentrations of Ni2+ that are toxic and life-threatening for many organism. Several lines of preliminary evidence suggest that members of the genus Sphingobium are able to grow in the presence of high concentrations of metal ions. We have isolated a novel Sphingobium strain (sp. ba1) able to grow in the presence of high concentrations (up to 20 mM) of NiCl2. Sequencing of its genome allowed the identification of several genes coding for proteins potentially involved in efflux-mediated resistance mechanisms. Here we use the RNA-seq approach to analyze the response of the Sphingobium sp. ba1 strain to high concentrations (10 mM) of Ni ions. Transcriptomic data show the differential expression of about one-hundred and twenty genes, most of which are up-regulated and encode proteins such as membrane proteins and components of metal efflux systems, enzymes involved in oxidative stress responses (catalases, peroxidases) and signal transduction systems.
Project description:The project aims to to understand the response of the lin genes in Sphingobium indicum B90A under the stress of HCH isomers and the metabolites formed during degradation of hexachlorocyclohexane (HCH). Entire cell proteome from Sphingobium indicum B90A was extracted in presence of four HCH isomers. Quantitative proteomics confirmed the constitutive expression of the linA, linB and linC genes of the HCH degradation pathway crucial for the initiation of HCH isomers degradation. LinM and LinN were upregulated in the presence of β- and δ-isomers suggested the important role of ABC transporter system in the depletion of β- and δ-HCH. Besides this HCH isomers induced oxidative stress caused systemic changes in strain B90A proteome.
Project description:Transcriptional profile of RNA extracted from Sphingobium sp. SYK-6 treated with 10 mM dehydrodiconiferyl alcohol (DCA), 10 mM vanillate, or SEMP (10 mM sucrose, 10 mM glutamate, 0.34 mM methionine, and 10 mM proline).