Influence of Soil Characteristics and Proximity to Antarctic Research Stations on Abundance of Antibiotic Resistance Genes in Soils

Abstract

Soil is an important environmental reservoir of antibiotic resistance genes (ARGs), which are increasingly recognized as environmental contaminants. Methods to assess the risks associated with the acquisition or transfer of resistance mechanisms are still underdeveloped. Quantification of background levels of antibiotic resistance genes and what alters those is a first step in understanding our environmental resistome. Toward this goal, 62 samples were collected over 3 years from soils near the 30-year old Gondwana Research Station and for 4 years before and during development of the new Jang Bogo Research Station, both at Terra Nova Bay in Antarctica. These sites reflect limited and more extensive human impact, respectively. A qPCR array with 384 primer sets targeting antibiotic resistance genes and mobile genetic elements (MGEs) was used to detect and quantify these genes. A total of 73 ARGs and MGEs encompassing eight major antibiotic resistance gene categories were detected, but most at very low levels. Antarctic soil appeared to be a common reservoir for seven ARGs since they were present in most samples (42%-88%). If the seven widespread genes were removed, there was a correlation between the relative abundance of MGEs and ARGs, more typical of contaminated sites. There was a relationship between ARG content and distance from both research stations, with a significant effect at the Jang Bogo Station especially when excluding the seven widespread genes; however, the relative abundance of ARGs did not increase over the 4 year period. Silt, clay, total organic carbon, and SiO were the top edaphic factors that correlated with ARG abundance. Overall, this study identifies that human activity and certain soil characteristics correlate with antibiotic resistance genes in these oligotrophic Antarctic soils and provides a baseline of ARGs and MGEs for future comparisons.

TCDD influences reservoir of antibiotic resistance genes in murine gut microbiome

“…Our own previous studies showed that 30-nM TCDDdosed batch reactors did not influence gut commensals (including Enterobacteriaceae) in vitro (Stedtfeld et al 2016). No effects were observed with 1-1000 nM TCDD on bacteria grown on agar plates (Lefever et al 2016).…”

“…S2B, Supporting Information) based on the rplB gene. Furthermore, TCDD tended (p = 0.06) to reduce the expression of TLR5 gene 2.0-fold in ileum of mice devoid of microbiota (Stedtfeld et al 2016).…”

“…All assays were described in previous studies (Wang et al 2016). qPCR reactions were performed on a Wafergen SmartChip Real-time PCR system as reported (Wang et al 2016). Sample and primers were dispensed into the SmartChip using a Multi-sample Nanodispenser.…”

“…Extracted DNA (30 μg per μl) was used for each sample, DNA extracted from individual groups was pooled and all qPCR reactions were run in triplicate. Cycling conditions and data processing were performed as previously described (Wang et al 2016). The 16S rRNA gene assay targeting Enterobacteriaceae (Barman et al 2008) was run separately on the Chromo4 BioRad using reagents and cycling parameters recommended with the Power SYBR Green PCR Master Mix.…”

“…In general, exposure can occur from food such as fish or dairy, and is partly the result of persistence and accumulation in river sediment and floodplains (Yamashita et al 2000). Following oral exposure, TCDD elicits an immunosuppressive response in the gut (Vorderstrasse et al 2001;Marshall et al 2008) that depletes immune cell populations and expression (Fader et al 2015;Stedtfeld et al 2016), and increases host susceptibility to infectious diseases including Salmonella, Trichinella spirali and Listeria (Thigpen et al 1975;Luebke et al 1994;Sugita-Konishi et al 2003). Since TCDD influences immune response and microbial dysbiosis, this study focused on the elicited impact on the reservoir of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) in the gut.…”