Abstract：
Antibiotics present in the natural environment would induce the generation of antibiotic-resistant bacteria (ARB), causing great environmental risks. The effects of antibiotic resistance genes (ARGs) and antibiotics on bacterial transport/deposition in porous media yet are unclear. By using E. coli without ARGs as antibiotic-susceptible bacteria (ASB) and their corresponding isogenic mutants with ARGs in plasmids as ARB, the effects of ARGs and antibiotics on bacterial transport in porous media were examined under different conditions (1-4 m/d flow rates and 5-100 mM NaCl solutions). The transport behaviors of ARB were comparable with those of ASB under antibiotic-free conditions, indicating that ARGs present within cells had negligible influence on bacterial transport in antibiotic-free solutions. Interestingly, antibiotics (5-1000 μg/L gentamicin) present in solutions increased the transport of both ARB and ASB with more significant enhancement for ASB. This changed bacterial transport induced by antibiotics held true in solution with humic acid, in river water and groundwater samples. Antibiotics enhanced the transport of ARB and ASB in porous media via different mechanisms (ARB: competition of deposition sites; ASB: enhanced motility and chemotaxis effects). Clearly, since ASB are likely to escape sites containing antibiotics, these locations are more likely to accumulate ARB and their environmental risks would increase.
摘要：
自然环境中存在的抗生素会诱导抗生素抗性细菌（ARB）的产生，造成巨大的环境风险。抗生素抗性基因（ARGs）和抗生素对多孔介质中细菌运输/沉积的影响尚不清楚。通过使用不含ARGs的大肠杆菌作为抗生素敏感菌（ASB）及其相应的质粒中具有ARGs的等基因突变体作为ARB，在不同条件下（1-4m/d流速和5-100mMNaCl溶液）检查了ARG和抗生素对多孔培养基中细菌转运的影响。在无抗生素条件下，ARB的运输行为与ASB的运输行为相当，表明细胞内存在的ARGs对无抗生素溶液中细菌转运的影响可忽略不计。有趣的是,溶液中存在的抗生素（5-1000μg/L庆大霉素）增加了ARB和ASB的转运，对ASB的增强更为显着。这种由抗生素诱导的改变的细菌运输在腐殖酸溶液中保持真实，在河水和地下水样本中。抗生素通过不同的机制增强了ARB和ASB在多孔介质中的转运(ARB:沉积位点的竞争;ASB:增强的运动性和趋化性效应)。显然,因为ASB很可能会逃离含有抗生素的部位，这些地点更有可能积累ARB，其环境风险也会增加。
