Effects of long‐term fertilization on the diversity of bacterial mercuric reductase gene in a Chinese upland soil

Abstract

Soil mercury (Hg) pollution has received considerable attention due to its neurotoxin effects and its potential risk to food safety. The microbial transformation of Hg plays a key role in reducing Hg toxicity by the mercuric reductase (MerA) conferred by genes arranged in the mer operon. This study investigated the effects of long-term fertilization on the diversity of bacterial mercuric reductase gene (merA), which specify the reduction of ionic Hg²⁺ to the volatile elemental form Hg⁰, in an agricultural soil with relatively high Hg content. The soil samples were collected from different treatments, including control without fertilizer (CK), fertilizer nitrogen (N), combined fertilizers (NPK) of N, phosphorus (P) and potassium (K), and NPK plus organic manure (NPK + OM). The merA gene diversity patterns were analyzed based on the merA clone libraries and sequencing measurements. Results showed that the merA gene diversity was influenced by soil variables depending on the fertilization practices. In particular, NH₄⁺ and NO₃⁻ contents had strong effect on the merA gene diversity pattern both in the N and NPK treatments, whereas the merA gene diversity pattern in NPK + OM treatment was distinctly influenced by the contents of organic matter, available P and K. These results suggested that long-term fertilization had significant influences on merA gene diversity, which could be helpful to understand the Hg reduction process and potentially serve microbial remediation of Hg contaminated soil.

Linkage between community diversity of sulfate-reducing microorganisms and methylmercury concentration in paddy soil

“…Most Hg in soil is detected as ionic Hg 2+ species and shows relatively low toxicity, however, it still poses some environmental risk due to potential for Hg methylation followed by bioamplification in soilplant systems (Meng et al 2010;Liu et al 2012). Earlier studies have examined microbial methylation of Hg in estuarine, wetland, and freshwater sediments (Gilmour et al 1992; Heyes et al 2006;Duran et al 2008;Todorova et al 2009), but little attention to date has been paid to the linkage between specific types of microorganism and Hg methylation in soil environments.…”

Analysis of the Microbial Community Structure by Monitoring an Hg Methylation Gene ( hgcA ) in Paddy Soils along an Hg Gradient

“…However, whether the genes contribute a selective advantage related to Hg concentration or toxicity remains unclear (20). Moreover, the effects of environmental factors on the community that possesses the genes are completely unknown, although distribution patterns of microorganisms are usually influenced by a variety of factors in the environment (e.g., environmental variables and spatial and time factors) (21)(22)(23)(24). Paddy soils represent a typical freshwater environment that usually produces anaerobic conditions attributed to oxygen depletion after flooding (25), in which inorganic Hg(II) may be methylated by some anaerobic microorganisms (26).…”

Impacts of long‐term fertilization on crop yield and microbial communities under rice–rapeseed rotation

“…These results showed that different nutrient fertilizer led to major changes in the relative abundance of particular bacterial communities (Miransari, 2011). Both long‐term and short‐term studies have found that the abundance of Acidobacteria decreased significantly with the increase of N fertilizer application, which was closely associated with soil pH value (Liu, Li, et al., 2020), while, in our study, the relative abundance of Acidobacteria , serving as typically oligotrophic bacteria in the recommended NPK fertilization, was higher than that in other fertilization, which was in contradiction with previous research (Eo & Park, 2016; Islam et al., 2012). This may be related to the increase in the special subgroup function of Acidobacteria , which, in terms of genus, were unclassified Subgroup 3 , unclassified Subgroup 6 , unclassified Subgroup 17 , and uncultured Desulfovirga sp .…”