Investigating a Novel Metabolic Pathway for Bacteria to Utilize L‐Ascorbate as its Carbon Source

Abstract

L‐Ascorbate (Vitamin C) is an abundant yet under‐researched carbon source present in the environment. L‐Ascorbate is a well‐known antioxidant that has significant effects of promoting tissue repair, strengthening bones, and boosting the immune system in mammals. Ralstonia eutropha H16 (Cupriavidus necator) is a saprotrophic soil bacterium that is commonly known for its ability to metabolize a great variety and number of substrates for growth and production of polyhydroxybutyrate (bioplastics). Ralstonia eutropha (ReH16) growth with L‐ascorbate was observed, but the pathway by which ReH16 metabolizes L‐ascorbate is unknown. Transcripts were quantified using RNAseq from cells grown with L‐ascorbate or other carbon sources. Putative pathway genes were identified as genes with transcripts upregulated greater than 50‐fold during L‐ascorbate growth. Transformation, conjugation, homologous recombination, and PCR analysis were used to generate and confirm targeted deletions of two pathway genes [h16_B0212 and h16_B1217]. Mutants of both genes were unable to grow with L‐ascorbate as their sole carbon source. Collaborators have characterized both enzymes. H16_B0212 is an aldehyde dehydrogenase that catalyzes oxidation of the δ‐carbon of α‐ketoglutarate semialdehyde. H16_B1217 is an enzyme that catalyzes the formation of a β‐lactone ring and transfer of a carboxyl group. Characterizing the L‐ascorbate metabolic pathway in Ralsontia eutropha will provide insight into a third, yet unknown pathway for L‐ascorbate metabolism.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.