title: Persistence of mitochondrial DNA markers as fecal indicators in water environments.
abstract: Mitochondrial DNA (mtDNA) polymerase chain reaction (PCR) technology has recently been developed to identify sources of fecal contamination, but information regarding environmental fate of mtDNA is limited. In this study, quantitative real-time PCR was used to determine the persistence of three species-specific mtDNA markers (human, pig and chicken) in river microcosms under different laboratory conditions and in dialysis tubes incubated in river environments during different seasons. Human feces had a higher abundance of mtDNA marker than pig and chicken feces. A biphasic decay pattern was observed for the mtDNA markers in microcosms incubated in darkness, and T90 (time needed for 90% reduction) ranged from 2.03 to 13.83 d. Each species-specific mtDNA marker persisted for relatively longer time at lower temperatures, and light exposure and predation increased the decay rates. Field experiments showed that the mtDNA markers could survive for longer time in winter (T90: 1.79-4.37 d) than in summer (T90: 0.60-0.75 d). Field application of mtDNA technology indicated that the markers were mainly distributed on the sites near animal breeding plants and had lower abundance in downstream water of the receiving river. This study expands our knowledge of the environmental fate of mtDNA markers and the results may be useful for practical application of the technology in fecal source tracking.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, China.
authors.forename: Xiwei
authors.initials: X
authors.lastname: He
authors.affiliation: Jiangsu Key Laboratory of Molecular Medicine, School of Medicine, Nanjing University, China. Electronic address: chenhuimei@nju.edu.cn.
authors.forename: Huimei
authors.initials: H
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Shi
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, China.
authors.forename: Yibin
authors.initials: Y
authors.lastname: Cui
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, China. Electronic address: zhangxx@nju.edu.cn.
authors.forename: Xu-Xiang
authors.initials: XX
authors.lastname: Zhang
mesh_terms: D004272:DNA, Mitochondrial / Q000032:analysis*; D004784:Environmental Monitoring / Q000379:methods*; D005243:Feces; D062065:Wastewater / Q000032:analysis*; D014871:Water Microbiology; D014876:Water Pollution / Q000032:analysis*
chemical_list: D004272:DNA, Mitochondrial; D062065:Wastewater
keywords: Decay rates; Fecal source tracking; Quantitative PCR; Water environment; mtDNA markers