Biology Department Seminar

The beta-proteobacterium Cupriavidus metallidurans CH34 (formerly Ralstonia metallidurans) is intensively studied for the resistance to heavy metals. Altogether, about 150 genes conferring resistance to Ag(I), As(III), As(V), Bi(III), Cd(II), Co(II), Cr(VI), Cu(I), Cu(II), Hg(II),Mn(II), Ni(II), Pb(II), Tl(I) and Zn(II) were identified (although some putatively) on the four replicons that are 3.5 Mb, 2.3 Mb, 240 kb (pMOL30), and 180 kb(pMOL28) in size. The plasmids pMOL28 and pMOL30 contain many resistance genes further maximising the already substantial tolerance of heavy metals governed by the chromosomal genes This “auxiliary” resistance is very likely linked to the presence of rare plasmid-borne genes for which no or very few orthologs were reported in over 100 bacterial genomes.
Until recently, C. metallidurans were mainly isolated from industrial, anthropogenic biotopes such as wastes or sediments of non-ferrous industrial plants. Lately, C. metallidurans and related species have been isolated from other harsh environments such as the assembly halls of spacecraft.
Apparently, these bacteria are well equipped to overcome acute stress and are able to survive in oligotrophic environments. Most of them are facultative chemolithotrophs able to use hydrogen as energy source (hydrogenotrophs) . Interestingly, genome data of C. metallidurans CH34 also indicate that the organism contains genes for carbon monoxide- and thiosulphate-dependant chemotrophy. In addition, the bacterium efficiently captures and expresses foreign DNA and displays many other signs of genomic plasticity (including a temperature triggered mutator phenotype and a high variety of Mobile Genetic Elements) allowing it to react to sudden environmental changes in anthropogenic biotopes.
In this respect, this intruiging organism was used as a model system in experiments designed to test the bacterial response to spaceflight (with an emphasis on microgravity and cosmic radiation) These experiments