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

Abstract

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 ({micro}APPJ). 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. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=80 SRC="FIGDIR/small/631878v1_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@119626eorg.highwire.dtl.DTLVardef@18d2973org.highwire.dtl.DTLVardef@9c5568org.highwire.dtl.DTLVardef@1ab4e58_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical abstractC_FLOATNO C_FIG HighlightsO_LIEnzymes with [FeS] clusters are rapidly inactivated by plasma C_LIO_LIClusters damaged by plasma are repaired in vivo using iron and cysteine C_LIO_LIOver-expression of sodA and katE completely prevents disruption of [FeS] clusters by plasma C_LIO_LIPlasma resistance is increased threefold by SodA and KatE over-production C_LIO_LIPre-adaptation of E. coli to O2- increases plasma tolerance C_LI