A Plastic Genome

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Science  22 Sep 2006:
Vol. 313, Issue 5794, pp. 1704
DOI: 10.1126/science.313.5794.1704a

Ralstonia eutropha H16 is a bacterium that can adjust to life on a variety of nutrients (as carbon and energy sources) and can survive periods of anoxia. Two skills are of particular interest: the ability to perform the Knallgas reaction and the storage of carbon in polyhydroxyalkanoate (PHA) granules. The former refers to the explosive combination of H2 and O2 (in a 2:1 ratio), which Ralstonia carries out in a traditional respiratory fashion, passing protons and electrons separately through membrane-bound carriers until they are added to O2 in a terminal oxidase complex to produce water. The latter was first detailed almost half a century ago and has led to the biodegradable thermoplastic Biopol and to polythioesters.

Pohlmann et al. report the sequence of the two Ralstonia chromosomes (∼7 Mb), providing an inventory of the many candidate enzymes involved in the synthesis, polymerization, depolymerization, and catabolism of PHAs. The large number of genes encoding β-ketothiolases and acetoacetyl-CoA reductases offers the potential for tinkering with substrate specificity to create an intracellular library of three- to five-carbon hydroxyacid monomers. — GJC

Nat. Biotechnol. 24, 10.1038/nbt1244 (2006).

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