Project description:Transcriptome studies confirm the nitrogen limited physiological state of both the wild-type and mutant cells. In addition, multiple differentially expressed genes involved in the synthesis and consumption of pools of acetyl-CoA, acetoacetyl-CoA and 3-hydroxybutyryl-CoA, key metabolites for PHA and TAG synthesis, were identified. An enrichment analysis of differentially expressed genes in the nitrogen starved wild-type versus the isogenic RHA1_ro02104 mutant strain identified genes in the mutant involved in fatty acid and lipid as well as genes involved in acyl-CoA hydrolysis and triacylglycerol degradation. An 8 x 15K array study using total RNA recovered from triplicate cultures of Rhodococcus jostii RHA1 under nitrogen rich and nitrogen starved conditions and triplicate cultures of Rhodococcus jostii RHA1 TadA-homolog deletion mutants (2104) under nitrogen rich and nitrogen starved conditions.
Project description:To further explore potential molecular mechanisms and pathways by which the presence or absence of the pGKT2 plasmid may be affecting the overall fitness cost in a transconjugant Rhodococcus jostii RHA1 strain, transcriptome studies were performed. Transcriptome experiments comparing RHA1 wild-type and RHA1 transconjugant strains grown in rich media confirmed the presence of the pGKT2 plasmid.
Project description:p-Hydroxycinnamates, such as p-coumarate and ferulate, are components of plant cell walls and have a number of commercial applications. Previously, we had shown that the soil Actinobacterium Rhodococcus jostii RHA1 (RHA1) grows on ferulate, catabolizing it via vanillate and the M-NM-2-ketoadipate pathway. We used transcriptomics to identify genes in RHA1 that were specifically up-regulated during growth on ferulate. These include three operons predicted to encode the uptake and M-NM-2-oxidative deacetylation of ferulate and p-coumarate: couHLT, couMNO and couR. A couL mutant did not grow on p-coumarate, ferulate or their dihydro derivatives, but grew on vanillate. Purified CouL catalyzed the thioesterification of several p-hydroxycinnamates. Among the tested substrates, the best were p-coumarate and caffeate (kcat/KM ~400 mM-1s-1), and sinapate was not transformed. Of these, p-coumarate was also RHA1M-bM-^@M-^Ys preferred growth substrate. Although the data indicate that p-hydroxycinnamates are catabolized via M-NM-2-oxidation, the pathway lacks a typical M-NM-2-ketothiolase. The data further suggest the involvement of two formaldehyde detoxification pathways in vanillate catabolism. This study augments our understanding of the bacterial catabolism of biomass and facilitates the production of aromatics from renewable feedstocks. Transcriptomes of R. jostii RHA1 from ferulate and benzoate cultures were analysed using Ion PGMTM system.
