Analysis of the genome sequence of the polyhydroxyalkanoate-(PHA) accumulating bacterium Ralstonia eutropha strain H16 revealed three homologues (PhaP2, PhaP3 and PhaP4) of the phasin protein PhaP1. PhaP1 is known to constitute the major component of the layer at the surface of poly(3-hydroxybutyrate), poly(3HB), granules. PhaP2, PhaP3 and PhaP4 exhibited 42, 49 and 45 % identity or 61, 62 and 63 % similarity to PhaP1, respectively. The calculated molecular masses of PhaP1, PhaP2, PhaP3 and PhaP4 were 20?0, 20?2, 19?6 and 20?2 kDa, respectively. RT-PCR analysis showed that phaP2, phaP3 and phaP4 were transcribed under conditions permissive for accumulation of poly(3HB). 2D PAGE of the poly(3HB) granule proteome and analysis of the detected proteins by MALDI-TOF clearly demonstrated that PhaP1, PhaP3 and PhaP4 are bound to the poly(3HB) granules in the cells. PhaP3 was expressed at a significantly higher level in PhaP1-negative mutants. Occurrence of an unknown protein with an N-terminal amino-acid sequence identical to that of PhaP2 in crude cellular extracts of R. eutropha had previously been shown by others. Although PhaP2 could not be localized in vivo on poly(3HB) granules, in vitro experiments clearly demonstrated binding of PhaP2 to these granules. Further analysis of complete or partial genomes of other poly(3HB)-accumulating bacteria revealed the existence of multiple phasin homologues in Ralstonia solanacearum, Burkholderia fungorum and Azotobacter vinelandii. These new and unexpected findings should affect our current models of PHA-granule structure and may also have a considerable impact on the establishment of heterologous production systems for PHAs.

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Carbon dioxide (CO₂) is an attractive one-carbon (C1) building block in terms of sustainability and abundance. However, its low reactivity limits applications in organic synthesis as typically high-energy reagents are required to drive transformations. Here, we present a redox-neutral C−H carboxylation of arenes and styrenes using a photocatalytic approach. Upon blue-light excitation, the anthrolate anion photocatalyst is able to reduce many aromatic compounds to their corresponding radical anions, which react with CO₂ to afford carboxylic acids. High-throughput screening and computational analysis suggest that a correct balance between electron affinity and nucleophilicity of substrates is essential. This novel methodology enables the carboxylation of numerous aromatic compounds, including many that are not tolerated in classical carboxylation chemistry. Over 50 examples of C−H functionalizations using CO₂ or ketones illustrate a broad applicability. The method opens new opportunities for late-stage C−H carboxylation and valorization of common arenes.