Insights into the Polyhydroxybutyrate Biosynthesis in Ralstonia solanacearum Using Parallel ¹³C Tracers and Comparative Genome Analysis

Abstract

Bacterial accumulation of poly­(3-hydroxybutyrate) [P­(3HB)] is a metabolic strategy often adopted to cope with challenging surroundings. Ralstonia solanacearum, a phytopathogen, seems to be an ideal candidate with inherent ability to accumulate this biodegradable polymer of high industrial relevance. This study is focused on investigating the metabolic networks that channel glucose into P­(3HB) using comparative genome analysis, 13C tracers, microscopy, gas chromatography-mass spectrometry (GC-MS), and proton nuclear magnetic resonance (1H NMR). Comparative genome annotation of 87 R. solanacearum strains confirmed the presence of a conserved P­(3HB) biosynthetic pathway genes in the chromosome. Parallel 13C glucose feeding ([1-13C], [1,2-13C]) analysis mapped the glucose oxidation to 3-hydroxybutyrate (3HB), the metabolic precursor of P­(3HB) via the Entner–Doudoroff pathway (ED pathway), potentially to meet the NADPH demands. Fluorescence microscopy, GC-MS, and 1H NMR analysis further confirmed the ability of R. solanacearum to accumulate P­(3HB) granules. In addition, it is demonstrated that the carbon/nitrogen (C/N) ratio influences the P­(3HB) yields, thereby highlighting the need to further optimize the bioprocessing parameters. This study provided key insights into the biosynthetic abilities of R. solanacearum as a promising P­(3HB) producer.

Unraveling thein plantagrowth of the plant pathogenRalstonia pseudosolanacearumby mathematical modeling

“…The appearance and subsequent decrease of 3-hydroxybutyrate (3HB) in infected tomato xylem sap was also reported (6). 3HB is the monomer of polyhydroxybutyrate (PHB), a carbon storage molecule largely accumulated in R. solanacearum (19,20). However, the appearance of this metabolite has not been observed in XMM.…”