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The occurrence of antibiotics and antibiotic resistance genes (ARGs) was quantified in water and sediment samples collected from a 72 km stretch of the Haihe River, China. Tetracycline resistance genes (tetW, tetQ, tetO, tetT, tetM, tetB, and tetS) were not detected by quantitative PCR in many samples. In contrast, sul1 and sul2 (coding for sulfonamide resistance) were present at relatively high concentrations in all (38) samples. The highest ARG concentrations detected were (7.8 ± 1.0) × 10(9) copies/g for sul1 and (1.7 ± 0.2) × 10(11) copies/g for sul2, in sediment samples collected during the summer. The corresponding total bacterial concentration (quantified with a universal 16S-rDNA probe) was (3.3 ± 0.4) × 10(12) cells/g. Sul1 and sul2 concentrations in sediments were 120-2000 times higher than that in water, indicating that sediments are an important ARG reservoir in the Haihe River. Statistical analysis indicated a positive correlation between the relative abundance of these ARGs (i.e., sul1/16S-rDNA and sul2/16S-rDNA) and the total concentration of sulfamethoxazole, sulfadiazine, plus sulfachlororyridazine, suggesting that sulfonamides exerted selective pressure for these ARGs. A class 1 integron was implicated in the propagation of sul1. Overall, the widespread distribution of sulfonamide ARGs underscores the need to better understand and mitigate their propagation in the environment and the associated risks to public health.

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Bioremediation is a cost-effective and eco-friendly approach to decontaminate soils polluted by petroleum hydrocarbons. However, this technique usually requires a long time due to the slow degradation rate by bacteria. By applying U-tube microbial fuel cells (MFCs) designed here, the degradation rate of petroleum hydrocarbons close to the anode (<1 cm) was enhanced by 120% from 6.9 ± 2.5% to 15.2 ± 0.6% with simultaneous 125 ± 7 C of charge output (0.85 ± 0.05 mW/m(2) , 1 kΩ) in the tested period (25 days). Hydrocarbon fingerprint analysis showed that the degradation rate of both alkanes and polycyclic aromatic hydrocarbons (PAHs) was accelerated. The decrease of initial water content from 33% to 28% and 23% resulted in a decrease on charge output and hydrocarbon degradation rate, which could be attributed to the increase of internal resistance. A salt accumulation was observed in each reactor due to the evaporation of water from the air-cathode, possibly inhibited the activity of exoelectrogenic bacteria (EB) and resulted in the elimination of the current at the end of the tested period. The number of hydrocarbon degradation bacteria (HDB) in soil close to the anode increased by nearly two orders of magnitude in the MFC assisted system (373 ± 56 × 10(3)  CFU/g-soil) than that in the disconnected control (8 ± 2 × 10(3)  CFU/g-soil), providing a solid evidence for in situ biostimulation of HDB growth by colonization of EB in the same system.