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Decoding the Nano-Silver Resistance Mechanism Switch: Targeted Strategies for Control

ABSTRACT: The increasing prevalence of silver nanoparticle (AgNP) resistances in bacteria,such as Escherichia coli(E. coli) has prompted investigations into resistance mechanisms, sparking a debate between flagellin-mediated AgNP precipitation and copper efflux pump (CusCFBA) activation. Our study unveils a sequential progression of AgNP resistance mechanisms, highlighting the regulatory role of envelope stress, including the CpxRA two-component signal transduction system (cpxRA), the phage shock protein systems (Psp), extracytoplasmic function sigma E factor (σE). Specifically, cyclic AgNP exposure amplifies membrane potential (ΔΨ) by 40%, initiating Phase I resistance characterized by flagellin-mediated AgNP precipitation. Prolonged exposure induces a decline in intracellular pH (ΔpH) and ΔΨ, triggering Phase II Ag tolerance via CusCFBA activation. The regulatory role of cell envelope stress in AgNP resistance transition was validated using knockout mutants, revealing a deficient Phase I/II transition in ΔcpxRA (disrupting the CpxRA signal transduction) or ΔpspABC (inactivation of Psp system) and complete abolition of resistance evolution in ΔrseA (deletion of anti-σ factor rseA gene and continuous expression of σE-dependent stress response).

ORGANISM(S): Escherichia coli str. K-12 substr. MG1655

PROVIDER: GSE275262 | GEO | 2024/12/31

REPOSITORIES: GEO

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Aminoglycoside heteroresistance in Enterobacter cloacae is driven by the cell envelope stress response.

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Bacillus subtilis Δ7ECF Pxyl-sigV + xylose vs Δ7ECF Pxyl-sigV - xylose , 168 + lysozyme vs 168 - lysozyme

Project description:To define the ECF sigma sigV - regulated genes during log growth phase in LB media under induction conditions for sigV The seven extracytoplasmic function (ECF) sigma (σ) factors of Bacillus subtilis are broadly implicated in resistance to antibiotics and other cell envelope stressors mediated, in part, by regulation of cell envelope synthesis and modification enzymes. We here define the regulon of σV as including at least 20 operons many of which are also regulated by σM, σX, or σW. The σV regulon is strongly and specifically induced by lysozyme and this induction is key to the intrinsic resistance of B. subtilis to lysozyme. Strains with null mutations in either sigV or in all seven ECF σ factor genes (Δ7ECF) have essentially equal increases in sensitivity to lysozyme. Induction of σV in the Δ7ECF background restores lysozyme resistance, whereas induction of σM, σX or σW does not. Lysozyme resistance results from the ability of σV to activate the transcription of two operons: the autoregulated sigV-rsiV-oatA-yrhK operon and dltABCDE. Genetic analyses reveal that oatA and dlt are largely redundant with respect to lysozyme sensitivity: single mutants are not affected in lysozyme sensitivity whereas a double oatA dltA mutant is as sensitive as a sigV null strain. Moreover, the triple sigV oatA dltA mutant is no more sensitive than the oatA dltA double mutant, indicating that there are no other σV-dependent genes necessary for lysozyme resistance. Thus, σV confers lysozyme resistance by activation of two cell wall modification pathways: O-acetylation of peptidoglycan catalyzed by OatA and D-alanylation of teichoic acids by DltABCDE.

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2014-12-02 | GSE63777 | GEO

Global analysis of genes induced during sporulation of Clostridium difficile

Project description:Purpose: The goal of this study was to identify genes whose expression is induced during sporulation in a Spo0A-, σF-, σE-, σG-, and σK-dependent manner. Methods: Whole genome RNA sequencing was performed on wildtype, spo0A-, sigF-, sigE-, sigG-, and sigK- C. difficile strains (strain 630 background; JIR8094 = parent strain), and the transcriptional profiles of the different mutants during growth on 70:30 agar plates were determined using an Illumina HiSeq1000. Results: This analysis identified 185 genes whose expression is collectively activated by sporulation sigma factors: 150 were σF-dependent, 150 were σE-dependent, 30 were σG-dependent, and 31 were σK-dependent. A total of 237 genes were identified as requiring Spo0A for their expression when sporulation was induced on the 70:30 plates. Conclusions: These results provide the first genome-wide transcriptional analysis of genes whose expression is induced by specific sporulation sigma factors in the Clostridia and highlight that diverse mechanisms regulate sporulation sigma factor activity in the Firmicutes. For example, in contrast with the B. subtilis sporulation pathway, C. difficile σE was not required to fully activate σG, and σG was not required to activate σK.

2013-08-10 | GSE45977 | GEO

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