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Iron-sulfur cluster proteins present the weak spot in plasma-treated Escherichia coli

Non-thermal atmospheric pressure plasmas have an antiseptic activity beneficial in different medical applications. In a genome-wide screening, hydrogen peroxide and superoxide were identified as key species contributing to the antibacterial effects of plasma while [FeS] cluster proteins emerged as potential cellular targets. We investigated the impact of plasma treatment on [FeS] cluster homeostasis in Escherichia coli treated for 1 min with the effluent of a microscale atmospheric pressure plasma jet (µAPPJ). Mutants defective in [FeS] cluster synthesis and maintenance lacking the SufBC2D scaffold protein complex or desulfurase IscS were hypersensitive to plasma treatment. Monitoring the activity of [FeS] cluster proteins of the tricarboxylic acid cycle (aconitase, fumarase, succinate dehydrogenase) and malate dehydrogenase (no [FeS] clusters), we identified cysteine, iron, superoxide dismutase, and catalase as determinants of plasma sensitivity. Survival rates, enzyme activity, and restoration of enzyme activity after plasma treatment were superior in mutants with elevated cysteine levels and in the wildtype under iron replete conditions. Mutants with elevated hydrogen peroxide and superoxide detoxification capacity over-expressing sodA and katE showed full protection from plasma-induced enzyme inactivation and survival rates increased from 34% (controls) to 87%. Our study indicates that metabolic and genetic adaptation of bacteria may result in plasma tolerance and resistance, respectively.

FieldValue
Publisher
Authors
Release Date
2025-02-06
Identifier
6e91034a-87ad-499e-a6da-813534dccb3e
Permanent Identifier (DOI)
Permanent Identifier (URI)
Is supplementing
Plasma Source Name
Plasma Source Application
Plasma Source Specification
Plasma Source Properties
Plasma was generated using a micro-scale atmospheric-pressure plasma jet (µAPPJ). The feed gas was a mixture of helium (1.4 slm, 5.0 purity) and oxygen (0.6%, 4.8 purity). The plasma was ignited at 13.56 MHz and 230 VRMS. For plasma treatment, 20 µl of aqueous samples were applied onto a filter paper (0.9 cm in diameter, Whatman, 3MM) and placed at a 4 mm distance to the nozzle of the jet.
Language
English (United States)
Plasma Source Procedure
20 µl (∼400 CFU) were applied onto a filter paper and exposed to the effluent of the µAPPJ for 30 s. Plasma was ignited or not, resulting in plasma-treated samples and gas controls, respectively. Directly after treatment, the filter paper was immersed in 1 ml NaCl (0.9% (w/v)) and mixed vigorously. The paper was removed, and the cell suspension plated onto LB agar for colony counting next day. CFU counts of the plasma-treated samples were set in relation to the corresponding gas controls yielding the survival rates. The plasma treatment time was set to 30 s, resulting in survival rates for the wild type without any empty vector between 0.4 and 0.5.
License
Plasma Medium Name
Plasma Medium Properties
He (1.4 slm, 5.0 purity) + oxygen (0.6%, 4.8 purity)
Plasma Target Name
Contact Name
Julia Bandow
Plasma Target Properties
E. coli BW25113
Plasma Target Procedure
E. coli BW25113 was used as wild type. All corresponding deletion mutants were derived from the KEIO collection of single-gene knockout mutants. Plasmids for over-expression originated from the ASKA collection. The double deletion mutant ΔsodAΔsodB (ΔsodAB) was generated by removing the kanamycin resistance cassette replacing the sodA gene in the ΔsodA strain and then inserting a kanamycin resistance cassette in the sodB locus using P1 phage transduction and standard protocols. Plasma sensitivity was determined as described previously. In short, bacterial cultures in logarithmic growth phase (OD600 = 0.3-0.6) were first diluted to an OD600 of 0.3 and then 1:5,000 in LB medium to give app. 20,000 CFU ml-1 prior to plasma treatment.
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Public
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