Effects of nano-TiO₂on antibiotic resistance transfer mediated by RP4 plasmid

Abstract

The potential risks of nano-materials and the spread of antibiotic resistance genes (ARGs) have become two major global public concerns. Studies have confirmed that nano-alumina can promote the spread of ARGs mediated by plasmids. Nano-titanium dioxide (TiO(2)), an excellent photocatalytic nano-material, has been widely used and is often present in aqueous environments. At various nano-material concentrations, bacterial density, matting time, and matting temperature, nano-TiO(2) can significantly promote the conjugation of RP4 plasmid in Escherichia coli. We developed a mathematical model to quantitatively describe the conjugation process and used this model to evaluate the effects of nano-TiO(2) on the spread of ARGs. We obtained analytical solutions for total and resistant bacteria, which were enumerated by the abundance of genetic loci unique to the plasmid and the chromosome using qPCR. Our results showed that the mathematic model was able to fit the experimental data well and can be used to quantitatively evaluate the effects of nano-TiO(2). According to our model, the presence of nano-TiO(2) decreased the bacterial growth rate from 0.0360 to 0.0323 min(-1) and increased the conjugative transfer rate from 6.69 × 10(-12) to 3.93 × 10(-10 )mL cell(-1) min(-1). These results indicate that nano-TiO(2) inhibited bacterial growth and promoted conjugation simultaneously. The data for morphology and mRNA expression also demonstrated this phenomenon. Our results confirm that environmental nano-TiO(2) may cause the spread of ARGs and thus poses an environmental risk. In addition, we provide a potential method for monitoring changes in ARGs that result from conjugation and evaluating the effects of antimicrobial substances on ARG expression.

Enhanced uptake of antibiotic resistance genes in the presence of nanoalumina

“…Our previous studies indicated that there is a risk of nanomaterials leading to the development of bacteria resistant to antibiotics. We confirmed that the horizontal transfer of intracellular antibiotic resistance genes (ARGs) occurred via conjugation that was stimulated between two bacteria of same and different genera (Escherichia coli and Salmonella) by the addition of nanoalumina or nano titanium dioxide (Qiu, et al, 2012;Qiu, et al, 2015). In addition, other chemicals or physical methods, such as ionic liquids, ultraviolet exposure and chlorination, could promote ARGs in mobile elements to undergo conjugative transfer between bacteria Luo et al 2014;Guo et al 2015).…”

The Occurrence of the Colistin Resistance Gene mcr-1 in the Haihe River (China)

“…In addition, it has been demonstrated that ARGs can transfer between organisms in water environments [35]. More importantly, some reports have shown that many kinds of contaminants in water, such as antibiotics, metals and nanomaterials, can promote the transmission of ARGs [36,37]. Even wastewater treatment processes and drinking water chlorination could significantly affect the efficiency of ARG transfer [38].…”

Aquatic animals promote antibiotic resistance gene dissemination in water via conjugation: Role of different regions within the zebra fish intestinal tract, and impact on fish intestinal microbiota

“…Q‐PCR was used to quantify the cat gene (chloramphenicol‐resistant gene) carried by donors (Calhoun & Swartz, ), the typical traG gene on the RP4 plasmid carried by both cultivable and uncultivable bacteria (Qiu et al., ), and the mRNA expression level of regulatory genes ( trbBp and trfAp ) involved in RP4‐mediated conjugal transfer using the absolute quantification method. 16S rRNA was used as the internal standard gene, which indicated presence of both cultivable and uncultivable bacteria.…”

“…The procedures of RNA extraction and reverse transcription were performed as described by the manufacturers. Finally, the mRNA expression level of the mating pair formation (Mpf) gene, trbBp and the DNA transfer and replication (Dtr) gene, trfAp , were quantified using corresponding primer pairs (Qiu et al., , ).…”