Patterns of Bacterial Diversity Along a Long-Term Mercury-Contaminated Gradient in the Paddy Soils
Mercury (Hg) pollution is usually regarded as an environmental stress in reducing microbial diversity and altering bacterial community structure. However, these results were based on relatively short-term studies, which might obscure the real response of microbial species to Hg contamination. Here, we analysed the bacterial abundance and community composition in paddy soils that have been potentially contaminated by Hg for more than 600 years. Expectedly, the soil Hg pollution significantly influenced the bacterial community structure. However, the bacterial abundance was significantly correlated with the soil organic matter content rather than the total Hg (THg) concentration. The bacterial alpha diversity increased at relatively low levels of THg and methylmercury (MeHg) and subsequently approached a plateau above 4.86 mg kg−1 THg or 18.62 ng g−1 MeHg, respectively. Contrasting with the general prediction of decreasing diversity along Hg stress, our results seem to be consistent with the intermediate disturbance hypotheses with the peak biological diversity under intermediate disturbance or stress. This result was partly supported by the inconsistent response of bacterial species to Hg stress. For instance, the relative abundance of Nitrospirae decreased, while that of Gemmatimonadetes increased significantly along the increasing soil THg and MeHg concentrations. In addition, the content of SO4 2−, THg, MeHg and soil depth were the four main factors influencing bacterial community structures based on the canonical correspondence analysis (CCA). Overall, our findings provide novel insight into the distribution patterns of bacterial community along the long-term Hg-contaminated gradient in paddy soils.
KeywordsBacterial Community Canonical Correspondence Analysis Paddy Soil Bacterial Community Structure Bacterial Abundance
This work was supported by the National Natural Science Foundation of China (41201523 and 41025004). We would like to thank Mr. Xing-Wang Shi for his assistance in soil sampling. We are also grateful to Jun-Tao Wang for his assistance in the data analysis.
- 14.Singh BK, Quince C, Macdonald CA, Khachane A, Thomas N, Al-Soud WA, Sørensen SJ, He Z, White D, Sinclair A, Crooks B, Zhou J, Campbell CD (2014) Loss of microbial diversity in soils is coincident with reductions in some specialized functions. Environ Microbiol. doi: 10.1111/1462-2920.12353 Google Scholar
- 26.Vishnivetskaya TA, Mosher JJ, Palumbo AV, Yang ZK, Podar M, Brown SD, Brook SC, Gu, Southworth GR, Drake MM, Brandt CC, Elias DA (2011) Mercury and Other Heavy metals influence bacterial community structure in contaminated Tennessee streams. Appl Environ Microbiol 77:302–311PubMedCentralCrossRefPubMedGoogle Scholar
- 30.Rothenberg SE, Feng XB (2012) Mercury cycling in a flooded rice paddy. J Geophys Res 117, G03003Google Scholar
- 32.Chen D, Jing M, Wang X (2005) Determination of methyl mercury in water and soil by HPLC–ICP-MS, Agilent Technologies. 8Google Scholar
- 41.Odum EP (1981) The effects of stress on the trajectory of ecological succession. In: Barrett GW, Rosenburg R (eds) Stress effects on natural ecosystems. Wiley, London, pp 43–47Google Scholar