title: Isolation and characterization of gallium resistant Pseudomonas aeruginosa mutants.
abstract: Pseudomonas aeruginosa PA14 cells resistant to the novel antimicrobial gallium nitrate (Ga) were developed using transposon mutagenesis and by selecting spontaneous mutants. The mutants showing the highest growth in the presence of Ga were selected for further characterization. These mutants showed 4- to 12-fold higher Ga minimal inhibitory growth concentrations and a greater than 8-fold increase in the minimum biofilm eliminating Ga concentration. Both types of mutants produced Ga resistant biofilms whereas the formation of wild-type biofilms was strongly inhibited by Ga. The gene interrupted in the transposon mutant was hitA, which encodes a periplasmic iron binding protein that delivers Fe³⁺ to the HitB iron permease; complementation of the mutant with the hitA gene restored the Ga sensitivity. This hitA mutant showed a 14-fold decrease in Ga internalization versus the wild-type strain, indicating that the HitAB system is also involved in the Ga uptake. Ga uptake in the spontaneous mutant was also lower, although no mutations were found in the hitAB genes. Instead, this mutant harbored 64 non-silent mutations in several genes including those of the phenazine pyocyanin biosynthesis. The spontaneous mutant produced 2-fold higher pyocyanin basal levels than the wild-type; the addition of this phenazine to wild-type cultures protected them from the Ga bacteriostatic effect. The present data indicate that mutations affecting Ga transport and probably pyocyanin biosynthesis enable cells to develop resistance to Ga.
authors.affiliation: Department of Biochemistry, National Institute of Cardiology, Mexico, D.F., Mexico. Electronic address: garrod13420@cardiologia.org.mx.
authors.forename: Rodolfo
authors.initials: R
authors.lastname: García-Contreras
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Lira-Silva
authors.forename: Ricardo
authors.initials: R
authors.lastname: Jasso-Chávez
authors.forename: Ismael L
authors.initials: IL
authors.lastname: Hernández-González
authors.forename: Toshinari
authors.initials: T
authors.lastname: Maeda
authors.forename: Takahiro
authors.initials: T
authors.lastname: Hashimoto
authors.forename: Fred C
authors.initials: FC
authors.lastname: Boogerd
authors.forename: Lili
authors.initials: L
authors.lastname: Sheng
authors.forename: Thomas K
authors.initials: TK
authors.lastname: Wood
authors.forename: Rafael
authors.initials: R
authors.lastname: Moreno-Sánchez
mesh_terms: D018441:Biofilms / Q000187:drug effects / Q000254:growth & development; D004251:DNA Transposable Elements; D024881:Drug Resistance, Bacterial; D005708:Gallium / Q000378:metabolism* / Q000633:toxicity*; D017353:Gene Deletion; D005816:Genetic Complementation Test; D008826:Microbial Sensitivity Tests; D016254:Mutagenesis, Insertional; D009154:Mutation; D011550:Pseudomonas aeruginosa / Q000235:genetics* / Q000378:metabolism* / Q000502:physiology
chemical_list: D004251:DNA Transposable Elements; D005708:Gallium; C027235:gallium nitrate
keywords: Gallium; HitAB permease; Pseudomonas aeruginosa; Pyocyanin; Resistance