Plasmid-Encoded Tetracycline Efflux Pump Protein Alters Bacterial Stress Responses and Ecological Fitness of Acinetobacter oleivorans

Abstract

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.

Co-selection of antibiotic and heavy metal resistance in freshwater bacteria

“…The latter requires conjugative plasmids and it is commonly observed in nature, even between organisms that are distantly related (Tazzyman and Bonhoeffer, 2014). Conjugative plasmids and/or transposons harbor not only constitutive genetic traits (responsible for their replication, spread, and maintenance) but also a variety of genes that are useful to survive under enhanced ecological pressure Hong et al, 2014;Norman et al, 2009Turner et al, 2002. More recently additional mechanisms of HGT have been proposed (summarized in Popa and Dagan, 2011), suggesting that we might even underestimate the rate of gene transfer.…”

Survival, Virulence Gene Expression and Difference in the Drug Susceptibility of Non-typhoidal Salmonella in Gut Physiological Conditions

“…For instance, there was a signi cant difference (p< 0.001) between the growth observed in Salmonella Weltevreden (SW9) and Salmonella Newport (SN36) on exposure to tetracycline, most likely due to the presence of different e ux mediated tetracycline resistance genes namely tetB in SW9 and tetG in SN36. This further adds to the notion that e ux mediated resistance does affect bacterial tness in the environment in which they live (Hong et al 2014). Similarly, the differential growth curve in the presence of chloramphenicol observed in the MDR serovars could be possibly due to the presence of catA1 in SW9 and oR in SN36, which code for chloramphenicol acetyl transferase and some speci c exporter proteins respectively (Schwarz et al 2004).…”

Tetracycline alters gene expression in Salmonella strains that harbor the Tn10 transposon

“…Furthermore, physiological alterations following acquisition of antibiotic resistance have been reported in the last years (Andersson, ; Kang and Park, ). Additionally, Tc itself and a Tc efflux pump have been associated to some of the physiological changes that occur in Acinetobacter oleivorans upon acquisition of plasmid pAST2 (Hong et al ., ).…”