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The genetic basis of cadmium resistance of B urkholderia cenocepacia
Author(s) -
Schwager Stephan,
Lumjiaktase Putthapoom,
Stöckli Martina,
Weisskopf Laure,
Eberl Leo
Publication year - 2012
Publication title -
environmental microbiology reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.229
H-Index - 69
ISSN - 1758-2229
DOI - 10.1111/j.1758-2229.2012.00372.x
Subject(s) - cadmium , gene , mutant , biology , microbiology and biotechnology , transposable element , biogenesis , green fluorescent protein , chemistry , genetics , organic chemistry
Summary B urkholderia species are highly resistant to heavy metals ( HMs ), yet their resistance mechanisms are largely unknown. In this study we screened 5000 mini‐ T n 5 transposon insertion mutants of B urkholderia cenocepacia H 111 for loss of cadmium tolerance. Of the four genes identified three affected outer membrane biogenesis and integrity or DNA repair. The fourth gene, BCAE 0587, encoded a P 1‐type ATPase belonging to the CadA family of HM exporters. CadA ‐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 cadA promoter to gfp 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 pH with an activation threshold of 30 nM cadmium. Inoculation of the HM ‐hyperaccumulating plant A rabidopsis halleri with a RFP ‐marked derivative of B . cenocepacia H 111 containing the P cadA – gfp fusion demonstrated the applicability of this biosensor for monitoring cadmium at the single cell level in a natural environment.