Influence of Altered Microbes on Soil Organic Carbon Availability in Karst Agricultural Soils Contaminated by Pb-Zn Tailings

Abstract

Soil organic carbon (SOC) availability is determined via a complex bio-mediated process, and Pb-Zn tailings are toxic to the soil microbes that are involved in this process. Here, Pb-Zn-tailings- contaminated karst soils with different levels (paddy field > corn field > citrus field > control group) were collected to explore the intrinsic relationship between Pb-Zn tailings and microbes due to the limited microbial abundance in these soils. The SOC concentration in the paddy fields is the highest. However, based on the soil microbial diversity and sole-carbon-source utilization profiles, the rate of SOC availability, McIntosh index, Shannon-Wiener diversity index, Simpson’s diversity index and species richness are the lowest in the rice paddy soils. According to the results of Illumina sequencing of the 16S rRNA gene, Acidobacteria and Proteobacteria are the dominant phyla in all samples, accounting for more than 70% of the reads, while the majority of the remaining reads belong to the phyla Verrucomicrobia, Chloroflexi, Actinobacteria, Bacteroidetes, and Nitrospirae. We also observed that their class, order, family, genus and operational taxonomic units (OTUs) were dependent on SOC availability. Pearson correlation analysis reveals that L-asparagine utilization profiles show significant positive correlation with OTUs 24, 75, and 109 (r = 0.383, 0.350, and 0.292, respectively), and malic acid utilization profiles show significant positive correlation with OTUs 4, 5, 19, 27 (Bradyrhizobium), 32 (Burkholderia), 75 and 109 (r = 0.286, 0.361, 0.387, 0.384, 0.363, 0.285, and 0.301, respectively), as also evidenced by the redundancy analysis (RDA) biplot and heat map. These results indicate that the most abundant groups of bacteria, especially the uncultured facultative Deltaproteobacteria GR-WP33-30 (OTU 24), after long-term acclimation in heavy metal-contaminated soil, are associated with the variance of labile carbon source such as L-asparagine and may have considerable control over the stability of the vast SOC pool in karst surface soils with different agricultural land-use practices. These findings can expand our understanding of global soil-carbon sequestration and storage via changes in microbial community structure of the most abundant species.

Transformation of Construction Cement to a Self-Healing Hybrid Binder

“…The FTIR analyses were performed with CEM I 42.5 R before and after water treatment (“CEM”; “hCEM”), as well as with CEM I 42.5 R supplemented with Na-polyP (“hCEM-polyP”), as described under Materials and Methods and shown in Figure 11A,B. All the samples show a complex group of bands between 1650 and 750 cm −1 [32,33] and the bands recorded can be attributed to signals, as described in the literature [34,35]. In general, within the range between 800 and 1200 cm −1 the stretching vibrations of Si-O (condensed silica) are recorded.…”

“…FTIR analyses [33,34] revealed that in polyP-containing cement the formation of the signal for Ca(OH) 2 decreased, followed by CaCO 3 formation. Together with the Si-based minerals the connected calcium silicate hydrate phase (C-S-H) became modulated, showing that Na-polyP retards the formation of C-S-H, a finding that might have an impact for future applications of polyP supplementation in cement for exploitation in practice.…”

16S rRNA Gene Amplicon Based Metagenomic Signatures of Rhizobiome Community in Rice Field During Various Growth Stages

“…Ca . Solibacter have a versatile genome which is adapted to breakdown complex recalcitrant organic compounds and carbohydrates and provides a suitable environmental condition for other microbes (Pearce et al, 2012; Rawat et al, 2012; Rime et al, 2015; Li et al, 2018). Previous reports have also highlighted their abundance in rhizosphere of black pepper (Umadevi et al, 2018), Panax notoginseng (Tan et al, 2017) and rice rhizosphere (Lopes et al, 2014).…”

Spatial and temporal dynamics of bacterioplankton community composition in a subtropical dammed karst river of southwestern China

“…The achieved 16S sequence data from 23 water samples were processed using the QIIME 1.7.0 software (Kuczynski et al, 2012;Li et al, 2018). Low-quality sequences with lengths below 150 bp and an average quality score below 30 were excluded.…”