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Frontiers of Environmental Science & Engineering

Front. Environ. Sci. Eng.    2020, Vol. 14 Issue (4) : 67
Validation of Bacteroidales-based microbial source tracking markers for pig fecal pollution and their application in two rivers of North China
Youfen Xu, Zong Li, Ruyin Liu(), Hongxia Liang, Zhisheng Yu, Hongxun Zhang
College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
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• Pig feces is the predominant excrement produced by animal husbandry in China.

• The PF, Pig-1-BacTaqMan, and Pig-2-BacTaqMan MST assays showed better performance.

• The pig-specific MST assays can contribute to managing the pig fecal pollution.

In China, pig feces is the predominant source of excrement produced by animal husbandry. Improper use or direct discharge of pig feces can result in contamination of natural water systems. Microbial source tracking (MST) technology can identify the sources of fecal pollution in environmental water, and contribute to the management of pig fecal pollution by local environmental protection agencies. However, the accuracy of such assays can be context-dependent, and they have not been comprehensively evaluated under Chinese conditions. We aimed to compare the performance of five previously reported pig-specific MST assays (PF, Pig-Bac1SYBR, Pig-Bac2SYBR, Pig-1-BacTaqMan, and Pig-2-BacTaqMan, which are based on Bacteroidales 16S rRNA gene markers) and apply them in two rivers of North China. We collected a total of 173 fecal samples from pigs, cows, goats, chickens, humans, and horses across China. The PF assay optimized in this study showed outstanding qualitative performance and achieved 100% specificity and sensitivity. However, the two SYBR green qPCR assays (Pig-Bac1SYBR and Pig-Bac2SYBR) cross-reacted with most non-pig fecal samples. In contrast, both the Pig-1-BacTaqMan and Pig-2-BacTaqMan assays gave 100% specificity and sensitivity. Of these, the Pig-2-BacTaqMan assay showed higher reproducibility. Our results regarding the specificity of these pig-specific MST assays differ from those reported in Thailand, Japan, and America. Using the PF and Pig-2-BacTaqMan assays, a field test comparing the levels of pig fecal pollution in rivers near a pig farm before and after comprehensive environmental pollution governance indicated that pig fecal pollution was effectively controlled at this location.

Keywords Microbial source tracking      Pig fecal pollution      16S rRNA gene markers      Pig-specific Bacteroidales     
Corresponding Author(s): Ruyin Liu   
Issue Date: 17 April 2020
 Cite this article:   
Youfen Xu,Zong Li,Ruyin Liu, et al. Validation of Bacteroidales-based microbial source tracking markers for pig fecal pollution and their application in two rivers of North China[J]. Front. Environ. Sci. Eng., 2020, 14(4): 67.
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Youfen Xu
Zong Li
Ruyin Liu
Hongxia Liang
Zhisheng Yu
Hongxun Zhang
Fig.1  Sampling locations for environmental waters.
Assay Primers or probes Sequence (5′– 3′) Final concentration Annealing temperature (°C) Amplicon size (bp)
PF (Bernhard and Field, 2000; Dick et al., 2005) PF163F GCGGATTAATACCGTATGA 1 mol/L 62 563
Pig-Bac1SYBR (Okabe et al., 2007) PS422F CGGGTTGTAAACTGCTTTTATGAAG 1 mol/L 62 150
Pig-Bac2SYBR (Okabe et al., 2007) Bac41F TACAGGCTTAACACATGCAAGTCG 1 mol/L 62 150
Pig-1-BacTaqMan (Mieszkin et al., 2009) Bac32F AACGCTAGCTACAGGCTTAAC 0.2 mol/L 60 129
Pig-2-BacTaqMan (Mieszkin et al., 2009) Bac41F2 GCATGAATTTAGCTTGCTAAATTTGAT 0.3 mol/L 60 116
Tab.1  Sequences of primers and probes used for pig-specific Bacteroidales assays
Assay Number of samples showing positive results Specificity Sensitivity Accuracy
Organism of origin
PF 80 0 0 0 0 0 100% 100% 100%
Pig-Bac1 77 19 14 11 16 4 35% 96% 61%
Pig-Bac2 80 22 16 18 19 4 15% 100% 54%
Pig-1-Bac 80 0 0 0 0 0 100% 100% 100%
Pig-2-Bac 80 0 0 0 0 0 100% 100% 100%
Tab.2  Performance of pig-specific Bacteroidales assays for detecting fecal samples
Assays C0a (log10 GC/g wet feces) Mean Ctb %CVc
Pig-1-Bac 7.95±1.55 20.60 21.30
Pig-2-Bac 9.20±1.03 20.73 17.94
P value of t-test 0.074 (>0.05)
Tab.3  Quantitative comparison of Pig-1-BacTaqMan and Pig-2-BacTaqMan assays for analyzing pig fecal samples
Fig.2  Boxplot representation of pig-specific marker concentration in fecal samples detected by Pig-1-BacTaqMan and Pig-2-BacTaqMan assays.
PF assay(n= 3) Sampling sites
H-1 H-2 H-3 H-4 H-5 J-6 J-7
Number of positive samples 2 3 1 3 3 0 3
Intensity of target band + + + + + + + + + + + +
Tab.4  Qualitative PF assay for environmental water samples before environmental governance.
Fig.3  Boxplot representation of concentration of the marker Pig-2-Bac in environmental water samples before environmental governance.
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