Abstract
BackgroundSoil contaminated with the heavy metal Cadmium (Cd) is a widespread problem in many parts of the world. Based on metagenomic analysis, we investigated the functional potential and structural diversity of the microbial community in Cd-contaminated and non-contaminated soil samples and we explored the associated metabolic pathway network in cluster of orthologous groups (COG) and Kyoto Encyclopedia of Genes and Genomes (KEGG).ResultsThe results showed that microorganisms in these soils were quite abundant, and many of them possessed numerous physiological functions. However, Cd-contamination has the potential to reduce the microbial diversity and further alter the community structure in the soil. Notably, function analysis of the crucial microorganisms (e. g. Proteobacteria, Sulfuricella and Thiobacillus) indicated that these bacteria and their corresponding physiological functions were important for the community to cope with Cd pollution. The COG annotation demonstrated that the predominant category was the microbial metabolism cluster in both soil samples, while the relative abundance of metabolic genes was increased in the Cd-contaminated soil. The KEGG annotation results exhibited that the non-contaminated soil had more genes, pathways, modules, orthologies and enzymes involved in metabolic pathways of microbial communities than the Cd-contaminated soil. The relative abundance of some dominant KEGG pathways increased in the Cd contaminated soil, and they were mostly enriched to the metabolism, biosynthesis and degradation of amino acids, fatty acids and nucleotides, which was related to Cd tolerance of the microorganisms.ConclusionsCd-contamination can decrease the taxonomic species of microbes in soil and change the soil microbial composition. The functional pathways involved in the soil change with microbial structure variation, many of which are related to the heavy metal tolerance of soil microbes. The Cd-contaminated soil microbes is a potential resource for exploring cadmium resistant or tolerant bacteria.
Highlights
Soil contaminated with the heavy metal Cadmium (Cd) is a widespread problem in many parts of the world
The results showed that the pH value, organic matter, total nitrogen, total phosphorus and total potassium content in the two samples coincide with the local large area soil
site 1 (S1) had more open reading frames (ORFs) when compared to site 2 (S2), which consisted with the distribution of contigs
Summary
Soil contaminated with the heavy metal Cadmium (Cd) is a widespread problem in many parts of the world. Heavy metal contamination of soil derived from agricultural or industrial activities is one of the most severe environmental pollution issues around the world [1, 2]. During the past several decades, soil contaminated by heavy metals has become a serious phenomenon in China [3], which is. Feng et al BMC Microbiology (2018) 18:11 problems, including reducing the microbial biodiversity, soil quality and crops yield, and threats animals and humans health via the food chain [7, 8]. Due to its good solubility in soil, cadmium can be absorbed by the crops planted in the soil and affect the crops’ s tomatal opening, transpiration, and photosynthesis [9]. Cd contamination has been found to significantly decrease the microbial numbers and diversity in the soil [13, 14], leading to the reduction of soil microbial biomass, the respiration rate of microbes and enzyme activity [15,16,17,18,19], and decreased utilization of carbon [20]
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