Fig. 4From: Efficient Cas9-based genome editing of Rhodobacter sphaeroides for metabolic engineeringa The PHB biosynthetic pathway of Rhodobacter sphaeroides. The annotation is based on KEGG. Enzymatic conversions are indicated by their EC numbers. Double arrowed reactions describe reversible reactions (ΔrG′° > − 30 kJ/mol [48]). Ac-CoA acetyl-CoA; AcAc-CoA acetoacetyl-CoA; (R)-3-HB (R)-3-hydroxybutanoate, (R)-3-HB-CoA (R)-3-hydroxybutanoyl-CoA, (S)-3-HB-CoA (S)-3-hydroxybutanoyl-CoA, Crot-CoA crotonyl-CoA; PHB: poly-β-hydroxybutyrate. The interrupted square indicates the metabolic step that is hypothesized to be catalysed by phaB and/or phbB. b Effect of the phaB (RSP_0747) and the phbB (RSP_3963) knockout, as well as of the combined knockout, on the C/N ratios of the generated mutants in nitrogen excess and limiting conditions on a defined medium. Lower C/N ratio’s indicate less PHB accumulation (Student’s t-test, *P < 0.05). c Effect of the phaB (RSP_0747) and the phbB (RSP_3963) knockout, as well as of the combined knockout, on the acids production and the PHB accumulation in Rhodobacter sphaeroides (Student’s t-test, ***P < 0.001). Concentrations of active biomass, PHB, pyruvate and oxo-glutarate were measured after 24 h cultivation in Sistrom’s minimal medium supplied with 1.0 g/L or 0.25 g/L of NH4Cl (Nitrogen excess and nitrogen limited conditions, respectively). Error bars indicate standard deviations from at least two replicatesBack to article page