| Objective:To investigate the distribution of antibiotic resistance genes and mobile genetic elements in farmland soil contaminated with heavy metals near a certain factory. To analyze the relationships among heavy metals levels, relative abundance of ARGs and relative abundance of MGEs.Methods:1. According to soil environmental monitoring technical guideline(HJ/T 166-166), mixed soil samples of 7 pieces of farmland were collected in March, June and October 2014, and January 2015 at different downwind distance to the factory in Henan province. Samples with distance to the factory 741 m, 943 m, 1514 m, 1617 m, 1777 m, 2103 m and 2556 m were named G1-G7 respectively.2. Nineteen kinds of antibiotic resistance genes and mobile genetic elements were detected by polymerase chain reaction. 4 kinds of mobile genetic elements were inti1, inti2, ISCR2. 15 kinds of antibiotic resistance genes were tet C, tet A, tet M, tet W, tet Q, tet E, sul1, sul2, bla-TEM, CTX-M-1, qnr B, qnr A, str A, SHV, ISCR2, qnr S.3. The relative abundance of inti1, sul1, sul2, tet A, tet M and tet W were detected by Real-time fluorescence quantitative PCR.4. All the data were analyzed using SPSS 21.0. Differences of positive rates on different time point and differen distance from the factory were analyzed through Fisher’s exact test. Kolmogorov-Smirnov test were used to inspect the normality of relative abundance. Kruskal-Wallis H, two related samples nonparametric tests and Wilcoxon signed rank sum test were used to analyzed the difference of relative abundance on different time point and different distance from the factory. The significant level was 0.05.Results:1. Eight kinds of antibiotic resistance genes were found positive including sul2, tet C, bla-TEM, sul1, tet A, str A, tet M and tet W. Mobile genetic elements int I1, int I2, and ISCR2 were positive in 7 pieces of farmland. Positive rates of antibiotic resistance genes were sul2(22/28, 78.6%), tet C(22/28, 78.6%), bla-TEM(18/28, 64.3%), sul1(15/28, 53.6%), tet A(11/28, 39.3%), str A(9/28, 32.2%), tet M(6/28, 21.4%) and tet W(3/28, 10.7%). And positive rates of Mobile genetic elements were inti1(18/28, 64.3%), inti2(3/28, 10.7%) and ISCR2(7/28, 25.0%) respectively. Gen Bank numbers were KT625466, KT625467, KT625472, KT625465, KU940035, KU940037, KT625468, KT625470, KT625469, KU940036, and KT625471 respectively.2. Positive rates of total genes detected in soil in each sample area were not found significantly different(P>0.05), but were significantly different in different sample area in March(P<0.05); there were no significantly difference found about each gene in different diatance sample areas(P>0.05), sul2, tet C, bla-TEM and inti1 in different times were significantly different(P<0.05), positive rates among different genes in each time point were all significantly different(P<0.05); and positive rates of different genes in G2, G6 were significantly different(P<0.05).3. The total relative abundance of total detected genes in March and June were significantly different(P<0.05), those from different times in G3, G4, G5 were significantly different(P<0.05); genes from different samples were not found significantly different(P>0.05); The relative abundances of inti1 from different times were significantly different(P<0.05). The relative abundance among different genes in G2 were significantly different(P<0.05), the relative abundance in October and January were significantly different(P<0.05).4. The relative abundance of inti1 and total detected genes were consistent, r=0.644, total sul and total tet were positively correlated, r=0.743, sul1 were positively correlated with tet genes(tet M, tet A, tet W), r =0.711, 0.519, 0.535, respectively. Sul2 was positively correlated with tet genes(tet M, tet A), r=0.480, 0.411, respectively. Significant correlation was also found between the relative abundance of tet W and tet M(r=0.742), sul1 and sul2(r=0.386).5. Relative abudance of total detected genes was correlated with As level in soil, r = 0.375. Relative abudance of sul1 were positively correlated with As, Cd, Zn, Cu levels(r =0.162~0.516). Relative abundances of tet W was positively correlated with Cu level, r = 0.375.Conclusions:1. Antibiotic resistance genes and mobile genetic elements sul2, tet C, bla-TEM, and inti1 are found common in farmland near the factory. Those Genes may vary with times, and still stabilize with distance to the factory.2. The distribution of inti1 and total detected genes, total sul and total tet are consistent respectively, r >0.644.3. The relative abundance of total detected genes may be influenced by the content of As. The relative abundance of sul1 may be influenced by the content of As, Cd, Zn, Cu. The relative abundance of tet W may be influenced by the content of Cu. |
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