FIG 2.

Growth on ethanolamine requires the PA4021 gene in P. aeruginosa PAO1. Ethanolamine was provided as the sole source of either carbon (A) or nitrogen (B) for growing WT P. aeruginosa PAO1 and its isogenic mutants: the ΔPA4021, ΔPA4022, Δeat, and ΔeutB mutants. (A) As a carbon source, the ΔPA4021 and ΔeutB mutants exhibited no growth on ethanolamine, whereas the ΔPA4022 mutant displayed reduced growth. In comparison, the ΔPA4021 and ΔPA4022 mutants generated cell densities identical to that of the WT on carbon sources that intercept with ethanolamine at key catabolic intermediates, such as acetaldehyde and acetate. These results indicate that the PA4021 and PA4022 genes are necessary for catabolism of ethanolamine and not acetaldehyde in general. (B) As a nitrogen source in the presence of succinate, the ΔPA4021 and ΔeutB mutants exhibited no growth on ethanolamine. In contrast, the growth of the ΔPA4022 mutant was identical to that of the WT, indicating that PA4022 is not required for the assimilation of ethanolamine as a nitrogen source. Strains were grown for 24 and 4.5 h on ethanolamine as a source of carbon and nitrogen, respectively. Significant differences in OD₆₀₀ values were determined using an analysis of variance (ANOVA) with Dunnett's post hoc test (α-value, 0.05) and are indicated with asterisks. Data points represent mean values (n = 3) ± standard deviations (SD).