Genome sequence of the bioplastic-producing ‘‘Knallgas’’ bacterium Ralstonia eutropha H16

The H2-oxidizing lithoautotrophic bacterium Ralstonia eutropha H16 is a metabolically versatile organism capable of subsisting, in the absence of organic growth substrates, on H2 and CO2 as its sole sources of energy and carbon. R. eutropha H16 first attracted biotechnological interest nearly 50 years ago with the realization that the organism’s ability to produce and store large amounts of poly[R-(–)-3-hydroxybutyrate] and other polyesters could be harnessed to make biodegradable plastics. Here we report the complete genome sequence of the two chromosomes of R. eutropha H16. Together, chromosome 1 (4,052,032 base pairs (bp)) and chromosome 2 (2,912,490 bp) encode 6,116 putative genes. Analysis of the genome sequence offers the genetic basis for exploiting the biotechnological potential of this organism and provides insights into its remarkable metabolic versatility

Two Similar Gene Clusters Coding for Enzymes of a New Type of Aerobic 2-Aminobenzoate (Anthranilate) Metabolism in the Bacterium Azoarcus evansii

In the β-proteobacterium Azoarcus evansii, the aerobic metabolism of 2-aminobenzoate (anthranilate), phenylacetate, and benzoate proceeds via three unprecedented pathways. The pathways have in common that all three substrates are initially activated to coenzyme A (CoA) thioesters and further processed in this form. The two initial steps of 2-aminobenzoate metabolism are catalyzed by a 2-aminobenzoate-CoA ligase forming 2-aminobenzoyl-CoA and by a 2-aminobenzoyl-CoA monooxygenase/reductase (ACMR) forming 2-amino-5-oxo-cyclohex-1-ene-1-carbonyl-CoA. Eight genes possibly involved in this pathway, including the genes encoding 2-aminobenzoate-CoA ligase and ACMR, were detected, cloned, and sequenced. The sequence of the ACMR gene showed that this enzyme is an 87-kDa fusion protein of two flavoproteins, a monooxygenase (similar to salicylate monooxygenase) and a reductase (similar to old yellow enzyme). Besides the genes for the initial two enzymes, genes for three enzymes of a β-oxidation pathway were found. A substrate binding protein of an ABC transport system, a MarR-like regulator, and a putative translation inhibitor protein were also encoded by the gene cluster. The data suggest that, after monooxygenation/reduction of 2-aminobenzoyl-CoA, the nonaromatic CoA thioester intermediate is metabolized further by β-oxidation. This implies that all subsequent intermediates are CoA thioesters and that the alicyclic carbon ring is not cleaved oxygenolytically. Surprisingly, the cluster of eight genes, which form an operon, is duplicated. The two copies differ only marginally within the coding regions but differ substantially in the respective intergenic regions. Both copies of the genes are coordinately expressed in cells grown aerobically on 2-aminobenzoate