Abundance of mobile genetic elements, antibiotic resistance traits, and catabolic genes in a BTEX contaminated aquifer measured by DNA microarray and culture-dependent analyses

摘要

Several studies indicate that mobile genetic elements (e.g. plasmids and transposons) play a significant role in the adaptation of microbial communities to contaminant exposure. However, only few field studies have been done to demonstrate this influence. In the present study we measured the abundance of mobile genetic elements, antibiotic resistance traits and catabolic genes in BTEX contaminated and non-contaminated sediment samples from an aquifer at an industrial site in the Czech Republic by application of cultivation-dependent and cultivation-independent techniques. We included the analysis of antibiotic resistance as these traits are often found on catabolic plasmids. Generally we observed culturable streptomycin, ampicillin, and chloram-phenicol resistant bacteria in all samples, kanamycin resistant bacteria in some samples, and tetracycline and mercury resistant bacteria in few samples. No correlation was found between the abundance of antibiotic resistant bacteria and the level of BTEX contamination, although high levels of kanamycin and chloramphenicol resistant bacteria were only found in the highly contaminated aquifer sediments. Experiments showed that the abundance of plasmid DNA was not significantly different in bacterial isolates retrieved from aquifer sediments with high or low levels of BTEX compounds. Also, there was no significant difference in the abundance of plasmid DNA isolated from kanamycin resistant bacteria compared to bacteria isolated from non-selective agar plates. In order to embrace the total indigenous bacterial population, microarray analyses are employed to investigate the possible correlation between the level of BTEX contamination and the incidence of plasmid, transposon, antibiotic resistance, and catabolic genes.