Interaction between arsenic metabolism genes and arsenic leads to a lose-lose situation

Integrated genome-transcriptome analysis unveiled the mechanism of Debaryomyces hansenii-mediated arsenic stress amelioration in rice

Globally, rice is becoming more vulnerable to arsenic (As) pollution, posing a serious threat to public food safety. Previously Debaryomyces hansenii was found to reduce grain As content of rice. To better understand the underlying mechanism, we performed a genome analysis to identify the key genes in D. hansenii responsible for As tolerance and plant growth promotion. Notably, genes related to As resistance (ARR, Ycf1, and Yap) were observed in the genome of D. hansenii. The presence of auxin pathway and glutathione metabolism-related genes may explain the plant growth-promoting potential and As tolerance mechanism of this novel yeast strain. The genome annotation of D. hansenii indicated that it contains a repertoire of genes encoding antioxidants, well corroborated with the in vitro studies of GST, GR, and glutathione content. In addition, the effect of D. hansenii on gene expression profiling of rice plants under As stress was also examined. The Kyoto Encyclopedia of Genes and Genomes (KEGG) database revealed 307 genes, annotated in D. hansenii-treated rice, related to metabolic pathways (184), photosynthesis (12), glutathione (10), tryptophan (4), and biosynthesis of secondary metabolite (117). Higher expression of regulatory elements like AUX/IAA and WRKY transcription factors (TFs), and defense-responsive genes dismutases, catalases, peroxiredoxin, and glutaredoxins during D. hansenii+As exposure was also observed. Combined analysis revealed that D. hansenii genes are contributing to stress mitigation in rice by supporting plant growth and As-tolerance. The study lays the foundation to develop yeast as a beneficial biofertilizer for As-prone areas.

Salinity causes differences in stratigraphic methane sources and sinks

Methane metabolism, driven by methanogenic and methanotrophic microorganisms, plays a pivotal role in the carbon cycle. As seawater intrusion and soil salinization rise due to global environmental shifts, understanding how salinity affects methane emissions, especially in deep strata, becomes imperative. Yet, insights into stratigraphic methane release under varying salinity conditions remain sparse. Here we investigate the effects of salinity on methane metabolism across terrestrial and coastal strata (15-40 m depth) through in situ and microcosm simulation studies. Coastal strata, exhibiting a salinity level five times greater than terrestrial strata, manifested a 12.05% decrease in total methane production, but a staggering 687.34% surge in methane oxidation, culminating in 146.31% diminished methane emissions. Salinity emerged as a significant factor shaping the methane-metabolizing microbial community's dynamics, impacting the methanogenic archaeal, methanotrophic archaeal, and methanotrophic bacterial communities by 16.53%, 27.25%, and 22.94%, respectively. Furthermore, microbial interactions influenced strata system methane metabolism. Metabolic pathway analyses suggested Atribacteria JS1's potential role in organic matter decomposition, facilitating methane production via Methanofastidiosales. This study thus offers a comprehensive lens to comprehend stratigraphic methane emission dynamics and the overarching factors modulating them.

Microbial consortia-mediated arsenic bioremediation in agricultural soils: Current status, challenges, and solutions

Arsenic poisoning in agricultural soil is caused by both natural and man-made processes, and it poses a major risk to crop production and human health. Soil quality, agricultural production, runoff, ingestion, leaching, and absorption by plants are all influenced by these processes. Microbial consortia have become a feasible bioremediation technique in response to the urgent need for appropriate remediation solutions. These diverse microbial populations collaborate to combat arsenic poisoning in soil by facilitating mechanisms including oxidation-reduction, methylation-demethylation, volatilization, immobilization, and arsenic mobilization. The current state, problems, and remedies for employing microbial consortia in arsenic bioremediation in agricultural soils are examined in this review. Among the elements affecting their success include diversity, activity, community organization, and environmental conditions. Also, we emphasize the sensitivity and accuracy limits of existing assessment techniques. While earlier reviews have addressed a variety of arsenic remediation options, this study stands out by concentrating on microbial consortia as a viable strategy for arsenic removal and presents performance evaluation and technical problems. This work gives vital insights for tackling the major issue of arsenic pollution in agricultural soils by explaining the potential methods and components involved in microbial consortium-mediated arsenic bioremediation.

Regulating sludge composting with percarbonate facilitated the methylation and detoxification of arsenic mediated via reactive oxygen species

This study purposed to demonstrate the impact of reactive oxygen species (ROS) on arsenic detoxification mechanism in sludge composting with percarbonate. In this study, sodium percarbonate was used as an additive. Adding sodium percarbonate increased the content of H2O2 and OH, which the experimental group (SPC) was higher than the control group (CK). In addition, it decreased the bioavailability of arsenic by 19.10%. Metagenomic analysis found that Firmicutes and Pseudomonas took an active part in the overall compost as the dominant bacteria of arsenic methylation. ROS positively correlated with arsenic oxidation and methylation genes (arsC, arsM), with the gene copy number of arsC and arsM increasing to 7.74 × 1012, 5.24 × 1012 in SPC. In summary, the passivation of arsenic could be achieved by adding percarbonate, which promoted the methylation of arsenic, reduced the toxicity of arsenic, and provided a new idea for the harmless management of sludge.

Arsenic interferes with spermatogenesis involving Rictor/mTORC2-mediated blood-testis barrier disruption in mice

Ingestion of arsenic interferes with spermatogenesis and increases the risk of male infertility, but the underlying mechanism remines unclear. In this study, we investigated spermatogenic injury with a focus on blood-testis barrier (BTB) disruption by administrating 5 mg/L and 15 mg/L arsenic orally to adult male mice for 60 d. Our results showed that arsenic exposure reduced sperm quality, altered testicular architecture, and impaired Sertoli cell junctions at the BTB. Analysis of BTB junctional proteins revealed that arsenic intake downregulated Claudin-11 expression and increased protein levels of β-catenin, N-cadherin, and Connexin-43. Aberrant localization of these membrane proteins was also observed in arsenic-treated mice. Meanwhile, arsenic exposure altered the components of Rictor/mTORC2 pathway in mouse testis, including inhibition of Rictor expression, reduced phosphorylation of protein kinase Cα (PKCα) and protein kinase B (PKB), and elevated matrix metalloproteinase-9 (MMP-9) levels. Furthermore, arsenic also induced testicular lipid peroxidative damage, inhibited antioxidant enzyme (T-SOD) activity, and caused glutathione (GSH) depletion. Our findings suggest that disruption of BTB integrity is one of the main factors responsible for the decline in sperm quality caused by arsenic. PKCα-mediated rearrangement of actin filaments and PKB/MMP-9-increased barrier permeability jointly contribute to arsenic-induced BTB disruption.