Plasmid-encoded tetracycline efflux pump protein alters bacterial stress responses and ecological fitness of Acinetobacter oleivorans

• Published in: PloS one 2014-09, Vol.9 (9), p.e107716-e107716
• Main Authors: Hong, Hyerim, Jung, Jaejoon, Park, Woojun
• Format: Article
• Language: English
• Subjects: Acinetobacter; Acinetobacter - cytology; Acinetobacter - drug effects; Acinetobacter - genetics; Acinetobacter - physiology; Alkanes - metabolism; Antibiotics; Bacteria; Bacterial Proteins - genetics; Biology and Life Sciences; Cell cycle; Cell Membrane - drug effects; Cell Membrane - metabolism; Chromosomes - genetics; Clonal deletion; Costs; Drug resistance; E coli; Ecological and Environmental Phenomena; Efflux; Environmental science; Escherichia coli; Fitness; Fluorescence; Gene deletion; Gene expression; Gene Expression Profiling; Gene Knockout Techniques; Genes; Genomes; Growth rate; Hydrophobicity; Integrity; Intracellular Space - drug effects; Intracellular Space - metabolism; Membrane permeability; Membrane proteins; Metabolism; Motility; Oxidative Stress - drug effects; Oxidative Stress - genetics; Permeability; Peroxide; Phenotype; Physical fitness; Pili; Plasmids; Plasmids - genetics; Proteins; Replication; Sequence Analysis, RNA; Signal transduction; Soil microorganisms; Soil permeability; Stress, Physiological - drug effects; Stress, Physiological - genetics; Superoxide; Swimming; Tetracycline - pharmacology; Tetracycline Resistance - genetics
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0107716

Acquisition of the extracellular tetracycline (TC) resistance plasmid pAST2 affected host gene expression and phenotype in the oil-degrading soil bacterium, Acinetobacter oleivorans DR1. Whole-transcriptome profiling of DR1 cells harboring pAST2 revealed that all the plasmid genes were highly expressed under TC conditions, and the expression levels of many host chromosomal genes were modulated by the presence of pAST2. The host energy burden imposed by replication of pAST2 led to (i) lowered ATP concentrations, (ii) downregulated expression of many genes involved in cellular growth, and (iii) reduced growth rate. Interestingly, some phenotypes were restored by deleting the plasmid-encoded efflux pump gene tetH, suggesting that the membrane integrity changes resulting from the incorporation of efflux pump proteins also resulted in altered host response under the tested conditions. Alteration of membrane integrity by tetH deletion was shown by measuring permeability of fluorescent probe and membrane hydrophobicity. The presence of the plasmid conferred peroxide and superoxide resistance to cells, but only peroxide resistance was diminished by tetH gene deletion, suggesting that the plasmid-encoded membrane-bound efflux pump protein provided peroxide resistance. The downregulation of fimbriae-related genes presumably led to reduced swimming motility, but this phenotype was recovered by tetH gene deletion. Our data suggest that not only the plasmid replication burden, but also its encoded efflux pump protein altered host chromosomal gene expression and phenotype, which also alters the ecological fitness of the host in the environment.