Fig. 3. Induction of efflux pumps by polyamine shock identifies spermine and spermidine as AmvA substrates.

a Growth of A. baumannii AB5075 and mutants in the presence of spermine and spermidine. Results are mean ± SD for two biological and two technical replicates. b Genomic context of amvAR in 172 A. baumannii strains. The genes are present in 100% of complete A. baumannii genomes in a region of very high synteny. Core genes are shown in dark blue, accessory genes in light blue, and the number of genomes possessing each gene path is indicated. Annotated gene functions are: 1—aceI PACE family transporter, 2—acetyl-CoA acyltransferase, 3—short-chain dehydrogenase/reductase, 4—MaoC domain protein dehydratase, 5—beta-lactamase, 6—hypothetical protein, 7—hypothetical protein, 8—dnaX DNA pol III subunit tau, 9—hypothetical protein, 10—phospholipase C, 11—thioesterase family protein, 12—iron-containing alcohol dehydrogenase. c Intracellular accumulation of ³H-spermidine in A. baumannii AB5075 and its AB5075::amvA mutant. Late exponential-phase cells were washed into assay buffer and incubated with 10.8 nM ³H-spermidine (see ‘Methods’), and the amount of accumulated radioactivity measured by liquid scintillation counting. Results shown are from three independent biological replicates. *p < 0.05, one-way ANOVA. d Growth of E. coli BL21 in the presence of spermidine and spermine, with or without AmvA overexpression. Results are mean ± SD for three biological and two technical replicates. e Growth of A. baumannii BAL062 and its ∆amvA mutant in the presence of spermidine and spermine. Results are mean ± SD for two biological and two technical replicates.