title: Influence of Dissolved Organic Matter on Tetracycline Bioavailability to an Antibiotic-Resistant Bacterium.
abstract: Complexation of tetracycline with dissolved organic matter (DOM) in aqueous solution could alter the bioavailability of tetracycline to bacteria, thereby alleviating selective pressure for development of antibiotic resistance. In this study, an Escherichia coli whole-cell bioreporter construct with antibiotic resistance genes coupled to green fluorescence protein was exposed to tetracycline in the presence of DOM derived from humic acids. Complexation between tetracycline and DOM diminished tetracycline bioavailability to E. coli, as indicated by reduced expression of antibiotic resistance genes. Increasing DOM concentration resulted in decreasing bioavailability of tetracycline to the bioreporter. Freely dissolved tetracycline (not complexed with DOM) was identified as the major fraction responsible for the rate and magnitude of antibiotic resistance genes expressed. Furthermore, adsorption of DOM on bacterial cell surfaces inhibited tetracycline diffusion into the bioreporter cells. The magnitude of the inhibition was related to the amount of DOM adsorbed and tetracycline affinity for the DOM. These findings provide novel insights into the mechanisms by which the bioavailability of tetracycline antibiotics to bacteria is reduced by DOM present in water. Agricultural lands receiving livestock manures commonly have elevated levels of both DOM and antibiotics; the DOM could suppress the bioavailability of antibiotics, hence reducing selective pressure on bacteria for development of antibiotic resistance.
authors.affiliation: Department of Plant, Soil and Microbial Sciences, Michigan State University , East Lansing, Michigan 48824, United States.|Institute of Organic Contaminant Control and Soil Remediation, College of Resource and Environmental Sciences, Nanjing Agricultural University , Nanjing, Jiangsu 210095, People's Republic of China.
authors.forename: Zeyou
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Department of Plant, Soil and Microbial Sciences, Michigan State University , East Lansing, Michigan 48824, United States.
authors.forename: Yingjie
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Plant, Soil and Microbial Sciences, Michigan State University , East Lansing, Michigan 48824, United States.|Institute of Organic Contaminant Control and Soil Remediation, College of Resource and Environmental Sciences, Nanjing Agricultural University , Nanjing, Jiangsu 210095, People's Republic of China.
authors.forename: Yanzheng
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Department of Plant, Soil and Microbial Sciences, Michigan State University , East Lansing, Michigan 48824, United States.
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Boyd
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University , Nanjing, Jiangsu 210093, People's Republic of China.
authors.forename: Dongqiang
authors.initials: D
authors.lastname: Zhu
authors.affiliation: Department of Plant, Soil and Microbial Sciences, Michigan State University , East Lansing, Michigan 48824, United States.
authors.forename: Hui
authors.initials: H
authors.lastname: Li
mesh_terms: D000327:Adsorption; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001682:Biological Availability; D004352:Drug Resistance, Microbial / Q000187:drug effects; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D006812:Humic Substances / Q000032:analysis; D013752:Tetracycline / Q000378:metabolism / Q000493:pharmacokinetics*; D013753:Tetracycline Resistance; D014867:Water / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000493:pharmacokinetics*
chemical_list: D000900:Anti-Bacterial Agents; D006812:Humic Substances; D014874:Water Pollutants, Chemical; D014867:Water; D013752:Tetracycline