Description:
<jats:title>Summary</jats:title><jats:p><jats:italic><jats:styled-content style="fixed-case">B</jats:styled-content>urkholderia</jats:italic> species are highly resistant to heavy metals (<jats:styled-content style="fixed-case">HMs</jats:styled-content>), yet their resistance mechanisms are largely unknown. In this study we screened 5000 mini‐<jats:styled-content style="fixed-case">T</jats:styled-content>n<jats:italic>5</jats:italic> transposon insertion mutants of <jats:italic><jats:styled-content style="fixed-case">B</jats:styled-content>urkholderia cenocepacia</jats:italic> <jats:styled-content style="fixed-case">H</jats:styled-content>111 for loss of cadmium tolerance. Of the four genes identified three affected outer membrane biogenesis and integrity or <jats:styled-content style="fixed-case">DNA</jats:styled-content> repair. The fourth gene, <jats:styled-content style="fixed-case">BCAE</jats:styled-content>0587, encoded a <jats:styled-content style="fixed-case">P</jats:styled-content>1‐type <jats:styled-content style="fixed-case">ATPase</jats:styled-content> belonging to the <jats:styled-content style="fixed-case">CadA</jats:styled-content> family of <jats:styled-content style="fixed-case">HM</jats:styled-content> exporters. <jats:styled-content style="fixed-case">CadA</jats:styled-content>‐deficient strains lost the ability to grow in the presence of cadmium, zinc and lead, whereas resistance to nickel, copper and cobalt was not affected. Expression studies using a transcriptional fusion of the <jats:italic><jats:styled-content style="fixed-case">cadA</jats:styled-content></jats:italic> promoter to <jats:italic><jats:styled-content style="fixed-case">gfp</jats:styled-content></jats:italic> confirmed this specificity, as induction was only observed in presence of cadmium, zinc and lead. The promoter activity was found to be highest at neutral <jats:styled-content style="fixed-case">pH</jats:styled-content> with an activation threshold of 30 <jats:styled-content style="fixed-case">nM</jats:styled-content> cadmium. Inoculation of the <jats:styled-content style="fixed-case">HM</jats:styled-content>‐hyperaccumulating plant <jats:italic><jats:styled-content style="fixed-case">A</jats:styled-content>rabidopsis halleri</jats:italic> with a <jats:styled-content style="fixed-case">RFP</jats:styled-content>‐marked derivative of <jats:italic><jats:styled-content style="fixed-case">B</jats:styled-content>. cenocepacia</jats:italic> <jats:styled-content style="fixed-case">H</jats:styled-content>111 containing the <jats:styled-content style="fixed-case">P<jats:italic><jats:sub>cadA</jats:sub></jats:italic></jats:styled-content>–<jats:italic><jats:styled-content style="fixed-case">gfp</jats:styled-content></jats:italic> fusion demonstrated the applicability of this biosensor for monitoring cadmium at the single cell level in a natural environment.</jats:p>