A Short-Term Response of Soil Microbial Communities to Cadmium and Organic Substrate Amendment in Long-Term Contaminated Soil by Toxic Elements

Abstract

Two long-term contaminated soils differing in contents of Pb, Zn, As, Cd were compared in a microcosm experiment for changes in microbial community structure and respiration after various treatments. We observed that the extent of long-term contamination (over 200 years) by toxic elements did not change the total numbers and diversity of bacteria but influenced their community composition. Namely, numbers of Actinobacteria determined by phylum specific qPCR increased and also the proportion of Actinobacteria and Chloroflexi increased in Illumina sequence libraries in the more contaminated soil. In the experiment, secondary disturbance by supplemented cadmium (doses from double to 100-fold the concentration in the original soil) and organic substrates (cellobiose or straw) increased bacterial diversity in the less contaminated soil and decreased it in the more contaminated soil. Respiration in the experiment was higher in the more contaminated soil in all treatments and correlated with bacterial numbers. Considering the most significant changes in bacterial community, it seemed that particularly Actinobacteria withstand contamination by toxic elements. The results proved higher resistance to secondary disturbance in terms of both, respiration and bacterial community structure in the less contaminated soil.

The Extremophilic Actinobacteria: From Microbes to Medicine

“…Furthermore, actinobacteria have astonishing capabilities in adapting contaminated soil and efficiently decomposing organic materials such as hemicellulose and lignin through the actions of their metabolites [12]. Apparently, these bacteria can be bioindicators to toxic contaminants due to their higher sensitivity in detecting toxic elements [13]. Their unique tolerance to these contaminants accompanied by their degradation, biostimulation, and bioaugmentation abilities have enabled them to be great candidates for the bioremediation of heavy metals and organic pollutants [14][15][16].…”

Compositional shifts in microbial communities in soils supplemented with iron oxide materials and inorganic fertilizer

“…A study on metal-contaminated river sedi- ments from the Montana Superfund site showed a stable metaltolerant community at the most contaminated sites with Beta and Gammaproteobacteria found predominantly from DGGEextracted bands (Bouskill et al, 2010). Bacterial communities of the less contaminated soil were found more homogeneous compared to that of the highly contaminated soil in a study with long-term contaminated soils with toxic elements including Pb, Zn, As, and Cd (Madrova et al, 2018). The study also suggested that, among soil bacterial communities, Actinobacteria can particularly withstand toxic elements.…”

“…Long-term exposure to toxic elements, such as Pb, Zn, As, and Cd, in soils, induces changes in bacterial composition, but not the bacterial diversity and total biomass. Additionally, in secondary disturbance experiments, an increase in Cd levels led to a decrease in soil bacterial diversity, while soil respiration increased with an increase in bacterial population (Madrova et al, 2018). Another study of microbial communities in river sediments with a metal-contaminated gradient revealed that microbial composition was significantly correlated with organic matter and metals (Bouskill et al, 2010).…”

“…The health of an ecosystem is highly dependent on its microbial community, which includes biomass, activities and interactions among the microorganisms (Madrova et al, 2018;Rogiers et al, 2021). Apart from geographical and natural factors, anthropogenic factors such as pollutants released into the environment also influence the activity and function of soil microbiota.…”

Chemical Speciation, Plant Uptake, and Toxicity of Heavy Metals in Agricultural Soils

“…Commercial plants are generally provided with optimum growing conditions, where deficiency or toxicity are not a factor, though food crops from areas that have high local metal contamination can become contaminated with heavy metals. The legacy of pollution from metals can persist in soils, and long-term contamination (>200 years) of soils with metals can alter the microbial community, which can render the soil more sensitive to additional disturbance, with consequences for decomposition of organic matter . This has implications for areas of the globe undergoing rapid economic growth, where metal contamination can threaten sustainability of the soil ecosystem in the long term.…”