A consecutive 4-year elevated air temperature shaped soil bacterial community structure and metabolic functional groups in the rhizosphere of black locust seedlings exposed to lead pollution

Correlation of heavy metals' exposure with the prevalence of coronary heart disease among US adults: findings of the US NHANES from 2003 to 2018

We sought to explore the association between heavy metal exposure and coronary heart disease (CHD) based on data from the US National Health and Nutrition Examination Survey (NHANES, 2003-2018). In the analyses, participants were all aged > 20 and had participated in heavy metal sub-tests with valid CHD status. The Mann-Kendall test was employed to assess the trends in heavy metals' exposure and the trends in CHD prevalence over 16 years. Spearman's rank correlation coefficient and a logistics regression (LR) model were used to estimate the association between heavy metals and CHD prevalence. 42,749 participants were included in our analyses, 1802 of whom had a CHD diagnosis. Total arsenic, dimethylarsonic acid, monomethylarsonic acid, barium, cadmium, lead, and antimony in urine, and cadmium, lead, and total mercury in blood all showed a substantial decreasing exposure level tendency over the 16 years (all Pfor trend < 0.05). CHD prevalence varied from 3.53 to 5.23% between 2003 and 2018. The correlation between 15 heavy metals and CHD ranges from - 0.238 to 0.910. There was also a significant positive correlation between total arsenic, monomethylarsonic acid, and thallium in urine and CHD by data release cycles (all P < 0.05). The cesium in urine showed a negative correlation with CHD (P < 0.05). We found that exposure trends of total arsenic, dimethylarsonic acid, monomethylarsonic acid, barium, cadmium, lead, and antimony in urine and blood decreased. CHD prevalence fluctuated, however. Moreover, total arsenic, monomethylarsonic acid, and thallium in urine all showed positive relationships with CHD, while cesium in urine showed a negative relationship with CHD.

Influence of temperature change on the immobilization of soil Pb and Zn by hydrochar: Roles of soil microbial modulation

Considering the potential effect of the ambient temperature on soil microorganisms during heavy metal immobilization by hydrochar, 60 days of soil incubation was conducted to explore the impact of ambient temperature (5, 25, and 35 °C) on the immobilization of Pb and Zn by chitosan-magnetic sawdust hydrochar (CMSH) and magnetic chitosan hydrochar (MCH). The results showed that soil pH was relatively high and total organic carbon (TOC) was slightly lower in the 35 °C treatment. The diethylenetriaminepentaacetic acid (DTPA) available state content decreased significantly with the temperature increasing. Meanwhile, the ratios of stable Pb and Zn in the sequential extraction method proposed by the European Community Bureau of Reference (BCR) gradually increased with increasing temperature. The heatmap based on microbial community showed that elevated temperature not only favored the enrichment of metal-stable phyla, such as Chloroflexi, but was also involved in inhibiting the growth of Firmicutes, Actinobacteriota, and Proteobacteria. Meanwhile, different genera (Fonticella and Bacillus) in the Firmicutes phylum had distinct responses to temperature as well as to heavy metal immobilization effects. Subsequently, redundancy analysis confirmed that Chloroflexi and Fonticella were positively correlated with temperature and stable state metal content, while Actinobacteriota and Bacillus were negatively correlated with temperature and were positively correlated with DTPA available metal content. Moreover, Pb and Zn indicators displayed significant correlations for the dominant genera (R² > 0.8, p < 0.02).

Bacterial and fungal diversities examined through high-throughput sequencing in response to lead contamination of tea garden soil

Several studies have indicated that the heavy-metal content in tea is increasing gradually. Researchers examining the soil of more than 100 tea gardens in China have observed that lead content was higher in some soils. The effect of lead contamination on soil microorganisms in tea gardens was studied to determine the effect of lead on the essential functions of microorganisms in a tea garden soil ecosystem. Previous studies on pot experiments adopted the method of adding a single instance of pollution, which failed to comprehensively simulate the characteristics of the slow accumulation of heavy metals in soil. This study designed with two pollution modes (multistage and single instance) determined the content of soil lead in different forms according to the European Community Bureau of Reference extraction procedure. The community structure, species diversity and functional abundance of soil bacteria and fungi were examined by high-throughput sequencing. We observed that the content of four forms of lead was higher in the multistage contamination mode than in the single instance contamination mode. The effects of lead contamination on bacteria differed significantly (p < 0.05), and the abundance and diversity of bacteria were higher in the multistage contamination mode than in the single instance contamination mode. The community structure of fungi was more affected by lead than was that of bacteria. The content of each lead form was the environmental factor most strongly affecting soil bacteria and fungi. The predicted main function of the bacterial community was amino acid transport and metabolism, and the trophic mode of the fungal community was mainly pathotroph-saprotroph. This study revealed changes in soil microorganisms caused by different forms of lead and contamination methods in tea garden soil and provide a theoretical basis for examining the effects of lead contamination on soil microorganisms.

Responsive change of crop-specific soil bacterial community to cadmium in farmlands surrounding mine area of Southeast China

In arable soils co-influenced by mining and farming, soil bacteria significantly affect metal (Cadmium, Cd) bioavailability and accumulation. To reveal the soil microecology response under this co-influence, three intersection areas (cornfield, vegetable field, and paddy field) were investigated. With a similar nutrient condition, the soils showed varied Cd levels (0.31-7.70 mg/kg), which was negatively related to the distance from mining water flow. Different soils showed varied microbial community structures, which were dominated by Chloroflexi (19.64-24.82%), Actinobacteria (15.49-31.96%), Acidobacteriota (9.46-20.31%), and Proteobacteria (11.88-14.57%) phyla. A strong correlation was observed between functional microbial taxon (e. g. Acidobacteriota), soil physicochemical properties, and Cd contents. The relative abundance of tolerant bacteria including Vicinamibacteraceae, Knoellia, Ardenticatenales, Lysobacter, etc. elevated with the increase of Cd, which contributed to the enrichment of heavy metal resistance genes (HRGs) and integration genes (intlI), thus enhancing the resistance to heavy metal pollution. Cd content rather than crop species was identified as the dominant factor that influenced the bacterial community. Nevertheless, the peculiar agrotype of the paddy field contributed to its higher HRGs and intlI abundance. These results provided fundamental information about the crop-specific physiochemical-bacterial interaction, which was helpful to evaluate agricultural environmental risk around the intersection of farmland and pollution sources.

Insight into functional microorganisms in wet–dry conversion to alleviate the toxicity of chromium fractions in red soil

Soil contamination with potentially toxic element such as chromium (Cr) poses a threat to the environment and human health. The environmental toxicity of Cr is related not only to the total Cr content but also to the distribution of Cr fractions. In this study, laboratory simulation experiments were conducted to explore the characteristics of Cr fractions and responses of the functional microbial community during dynamic leaching and static drying processes. The results showed that acid-soluble Cr and reducible Cr transformed into other relatively stable fractions under dry conditions, and ammonium nitrogen promoted the transformation. Nitrate-nitrogen was significantly positively correlated with Cr fractions in the wet stage (p < 0.05), while ammonium nitrogen showed the same relation in the dry process. Analysis of the microbial community showed that the bacterial and fungal genera Flavihumibacter, Altererythrobacter, Methylobacillus, Flavisolibacter, Lysobacter, and Cladosporium were related to the Cr fractions (acid-soluble Cr, reducible Cr, and oxidizable Cr) under wet conditions, while the microbial genera Ellin6067, MND1, and Ramlibacter were related to Cr fractions under dry conditions. Moreover, the proliferation of the functional microbial genera Methylobacillus, Ellin6067, and MND1 related to Cr fractions in the wet–dry conversion process alleviated the environmental toxicity of Cr. These findings provide useful information for the remediation of Cr-contaminated soils by monitoring the distribution fractions of Cr and the functional microbial community under wet–dry conditions.

Nitrogen addition exerts a stronger effect than elevated temperature on soil available nitrogen and relation to soil microbial properties in the rhizosphere of Camellia sinensis L. seedlings

As the global climate changes, elevated atmospheric temperature and nitrogen (N) deposition co-occur in natural ecosystems, which affects rhizosphere soil nutrient by altering allocation of roots and its availability to soil microorganism. Elevated temperature in combination with N deposition is expected to affect soil available N and its relation to microbial properties, but this issue has not been extensively examined. Here, we investigated soil available N and its relation to microbial properties in rhizosphere of Camellia sinensis L. seedlings exposed to elevated temperature using a passive warming device in combination with N-added soil. Elevated temperature did not significantly affect soil pH, total organic carbon (TOC), total nitrogen (TN), the ratio of carbon and nitrogen (C:N ratio), total phosphorus (TP), available N ((N in ammonium (NH₄⁺-N) and N in nitrate (NO₃^--N)) (NH₄⁺-N + NO₃^--N)/TN, α-glucosidase (αG), β-glucosidase (βG), cellobiohydrolase (CBH), N-acetyl-glucosaminidase (NAG), and phenol oxidase (PPO) activities, while significantly stimulated root total length of tea seedlings (3.9%), root dry biomass (10.2%), soil microbial biomass carbon (MBC) (7.4%), microbial biomass nitrogen (MBN) (8.6%), and acid phosphatase (ACP) (8.8%). While N addition significantly (p < 0.05) stimulated root dry biomass of tea seedlings (14.1%), root total length (6.2%), root average diameter (6.7%), soil TN, available N, (NH₄⁺-N + NO₃^--N)/TN, and MBN under elevated temperature. Soil aG, βG, CBH, and ACP activity increase significantly (p < 0.05) under elevated temperature + N relative to elevated temperature alone. Generally, N addition led to increased available nitrogen and microbial properties in rhizosphere soil of tea seedlings exposed to elevated temperature by stimulating root properties, soil nitrogen, microbial biomass N, and enzyme activity. Redundancy analysis and Pearson correlation analysis suggested that N addition lead to higher correlation between soil available N and microbial properties exposed to elevated temperature. Our results indicated nitrogen addition exerts a stronger effect than elevated temperature on soil fertility and microbiological cycle in the rhizosphere of Camellia sinensis L. seedlings. The conclusion helps us understand the response mechanism of soil rhizosphere microenvironment to N deposition under global warming scenarios.

Possible effects of temperature on bacterial communities in the rhizosphere of rice under different climatic regions

Global warming is an indisputable fact. However, the effect of warming on the rhizosphere bacterial community of crops is not well understood. Therefore, we carried out pot experiments with three rice (Oryza sativa L.) varieties in black soil across three climatic regions of northeast China to simulate temperature change, and analyzed the response of the rhizosphere bacterial community to different temperatures. Results showed that climate had stronger effects on rhizosphere bacterial communities than rice variety. The rhizosphere bacterial diversity differed significantly among the three climatic regions and positively correlated with the mean daily average temperature (MAveT), mean daily maximum temperature (MMaxT), and mean daily minimum temperature (MMinT), and negatively correlated with the daily temperature range (DTR). Principal co-ordinate analysis revealed that bulk soil bacterial communities maintained a high similarity across the three climatic regions, while rhizosphere bacterial communities notably varied. This change was significantly correlated with MAveT, MMaxT, MMinT, and DTR. Compared with bulk soil, Proteobacteria and Bacteroidetes were enriched in the rhizosphere, while Actinobacteria was depleted. Moreover, these changes were strengthened by increasing the temperature and decreasing DTR. Additionally, correlation analysis revealed that changes in rhizosphere bacterial communities were closely related to the formation of rice yields. Our study revealed that the increasing temperature indirectly reshapes the rhizosphere bacterial community that may promote rice production in areas with lower temperatures.

Impact of microplastics on bioaccumulation of heavy metals in rape (Brassica napus L.)

Microplastics have become a global environmental problem due to the ubiquitous existence. The impacts of microplastics on heavy metals behaviors in aquatic environment are widely investigated, however, the impacts of microplastics on bioaccumulation of heavy metals in vegetables in terrestrial environment are seldom investigated. Herein, batch experiments were carried out, the microplastics (0.001%, 0.01%, 0.1%) and heavy metal (50, 100 mg/kg Cu²⁺ or 25, 50 mg/kg Pb²⁺) were single or combined spiked into soil to cultivate rapes (Brassica napus L.) in greenhouse. Copper and lead contents of rapes in MP0.1+Cu100 and MP0.1+Pb50 treatments reached 38.9 mg/kg and 9.4 mg/kg, which were significantly (p < 0.05) higher than those of Cu100 (35.3 mg/kg) and Pb50 (8.7 mg/kg) treatments, respectively. Results showed that microplastics in soil would facilitate heavy metals entering rape plants. In addition, contents of total chlorophyll, soluble sugar, vitamin C, malondialdehyde contents, activities of superoxide dismutase and guaiacol peroxidase, as well as related gene expression were analyzed to investigate the toxic effects of these pollutants (microplastics, Cu, and Pb) to rape plants. Malondialdehyde contents of rapes in MP0.1+Cu50, MP0.1+Cu100, MP0.1+Pb25, and MP0.1+Pb50 treatments reached 0.102 mmol/mg Protein, 0.123 mmol/mg Protein, 0.101 mmol/mg Protein, and 0.119 mmol/mg Protein, which were 1.42, 1.37, 1.46, and 1.45 times of those in Cu50, Cu100, Pb25, and Pb50 treatments, respectively. The changes of malondialdehyde content, activities of superoxide dismutase and guaiacol peroxidase, as well as contents of sugar and vitamin C indicated that microplastics in soil would bring severer damage and deteriorate quality of rape plants. The data in this study indicated that microplastics would increase the bioaccumulation of heavy metals in vegetables and damage to vegetables.

Microbiome analysis reveals the alterations in gut microbiota in different intestinal segments of Yimeng black goats

Mounting evidence revealed the importance of gut microbiota in host metabolism, immunity and physiology, and health. Yimeng black goats (YBGs) mainly distributed in Shandong province of China, displayed a complicated intestinal microecosystem, but studies of its gut microbiota are still insufficient to report. Therefore, this study was performed with an objective to characterize the intestinal microbial community structure and diversity in the small intestine (duodenum, jejunum and ileum) and cecum of YBGs and investigated the variability of gut microbiota of different intestinal segments. A total of 12 intestinal samples were collected from YBGs for high-throughput sequencing analysis based on V3-V4 variable region of 16S rRNA genes. Our results revealed alterations in gut microbial composition with obvious differences in relative abundance between the different intestinal segments. Additionally, small intestine including duodenum, jejunum and ileum not only displayed higher species abundance and diversity than cecum but also showed a significant difference among the main components of gut microbiota based on the analytical results of alpha and beta diversities. At the phylum level, Firmicutes and Proteobacteria were the most preponderant phyla in all the samples regardless of intestinal sites. Moreover, the microbiota in small intestine was significantly different from cecum, which were characterized by the higher relative abundance of Butyrivibrio_2, Megasphaera, Halomonas, Delftia, Hydrogenophaga, Limnobacter, Pseudoxanthomonas, Novosphingobium, Janibacter and Erythrobacter, whereas the levels of Butyricicoccus, unidentified_Lachnospiraceae, Fusicatenibacter, Akkermansia, Ruminococcaceae_NK4A214_group and Lactobacillus were lower. Overall, this study first characterized the profile of gut microbiota composition in different intestinal sites and provide better insight into intestinal microbial community structure and diversity of YBGs.