Acetate scavenging and aromatic funneling of lignocellulose-derived carbon in the denitrifier Pseudomonas veronii.

Pseudomonas veronii strain B19 funnels lignin-derived aromatics via a complete β-ketoadipate route and couples acetate assimilation to denitrification under limited O2.

• Why it matters: Denitrification and lignocellulose breakdown co-occur in soils and sediments with fluctuating or limited oxygen, but how facultative denitrifiers link aromatic carbon turnover to nitrate respiration is unclear.
• What they did: The isolate was grown on hemicellulose- and lignin-derived substrates under oxic and denitrifying conditions, combining genome analysis with proteomics and electron flow measurements.
• The result: Carbon source governed denitrification regulation: glucose caused bet hedging and transient nitrite accumulation at the oxic-anoxic transition, while xylan-derived acetate enabled a seamless transition; on alkali-solubilized lignin, denitrifying conversion was partial with vanillate accumulation and electron-limited but stoichiometrically efficient nitrate reduction at minimal N2O formation.