Growth and gene expression of Pseudomonas nitroreducens TX1 on octylphenol polyethoxylate surfactants

Pseudomonas nitroreducens ATCC PTA-6168 (also named TX1) efficiently grows on non-ionic surfactants as the sole source of carbon and energy aerobically. The global gene expression and bacterial stress responses during degradation remain further investigated. This study compared the growth, viability, and transcriptomic profiles of strain TX1 during the log phase when grown on minimal salts basal medium supplemented with 0.5% octylphenol polyethoxylates (OPEO_n, commercial name Triton^® X-100) vs. in 0.5% succinate. Differentially expressed genes were identified, with 219 upregulated and 22 downregulated. Gene ontology analysis revealed upregulation of oxidoreductase activity (53%), electrotransfer activity (11%), heme/FAD/cofactor binding (11/19/27%), and membrane (42%)-related functions. In ethanol oxidation, adh18 and adh19 (for two pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenases), aldh1 and aldh2 (for two aldehyde dehydrogenases), c₅₅₀ (for cytochrome c₅₅₀), and pqqABCDEF (for PQQ biosynthesis proteins) and aceA (for isocitrate lyase) and aceB (for malate synthase) acting in the glyoxylate cycle were upregulated. In addition to the above genes, the expression level of the representative genes from fatty acid degradation and chemotaxis was verified by RT-qPCR. The global gene expression of P. nitroreducens TX1 provides candidate genes involved in the bacteria grown on nonionic surfactants. KEY POINTS: • Growth characteristics of Pseudomonas nitroreducens ATCC PTA-6168 on surfactants • Differentially expressed genes related to growth on surfactants were identified • The ethanol oxidation system was upregulated when grown on surfactants.