Capability for arsenic mobilization in groundwater is distributed across broad phylogenetic lineages

Metalloproteome of human-infective RNA viruses: a study towards understanding the role of metal ions in virology

Metalloproteins and metal-based inhibitors have been shown to effectively combat infectious diseases, particularly those caused by RNA viruses. In this study, a diverse set of bioinformatics methods was employed to identify metal-binding proteins of human RNA viruses. Seventy-three viral proteins with a high probability of being metal-binding proteins were identified. These proteins included 40 zinc-, 47 magnesium- and 14 manganese-binding proteins belonging to 29 viral species and eight significant viral families, including Coronaviridae, Flaviviridae and Retroviridae. Further functional characterization has revealed that these proteins play a critical role in several viral processes, including viral replication, fusion and host viral entry. They fall under the essential categories of viral proteins, including polymerase and protease enzymes. Magnesium ion is abundantly predicted to interact with these viral enzymes, followed by zinc. In addition, this study also examined the evolutionary aspects of predicted viral metalloproteins, offering essential insights into the metal utilization patterns among different viral species. The analysis indicates that the metal utilization patterns are conserved within the functional classes of the proteins. In conclusion, the findings of this study provide significant knowledge on viral metalloproteins that can serve as a valuable foundation for future research in this area.

Impact of beaver ponds on biogeochemistry of organic carbon and nitrogen along a fire-impacted stream

Wildfires, which are increasing in frequency and severity in the western U.S., impact water quality through increases in erosion, and transport of nutrients and metals. Meanwhile, beaver populations have been increasing since the early 1900s, and the ponds they create slow or impound hydrologic and elemental fluxes, increase soil saturation, and have a high potential to transform redox active elements (e.g., oxygen, nitrogen, sulfur, and metals). However, it remains unknown how the presence of beaver ponds in burned watersheds may impact retention and transformation of chemical constituents originating in burned uplands (e.g., pyrogenic dissolved organic matter; pyDOM) and the consequences for downstream water quality. Here, we investigate the impact of beaver ponds on the chemical properties and molecular composition of dissolved forms of C and N, and the microbial functional potential encoded within these environments. The chemistry and microbiology of surface water and sediment changed along a stream sequence starting upstream of fire and flowing through multiple beaver ponds and interconnecting stream reaches within a burned high-elevation forest watershed. The relative abundance of N-containing compounds increased in surface water of the burned beaver ponds, which corresponded to lower C/N and O/C, and higher aromaticity as characterized by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The resident microbial communities lack the capacity to process such aromatic pyDOM, though genomic analyses demonstrate their potential to metabolize various compounds in the anaerobic sediments of the beaver ponds. Collectively, this work highlights the role of beaver ponds as biological "hotspots" with unique biogeochemistry in fire-impacted systems.

Hydrous ferric oxides (HFO's) precipitated from contaminated waters at several abandoned Sb deposits - Interdisciplinary assessment

The presented paper represents a comprehensive analysis of ochre sediments precipitated from Fe rich drainage waters contaminated by arsenic and antimony. Ochre samples from three abandoned Sb deposits were collected in three different seasons and were characterized from the mineralogical, geochemical, and microbiological point of view. They were formed mainly by poorly crystallized 2-line ferrihydrite, with the content of arsenic in samples ranging from 7 g·kg^-1 to 130 g·kg^-1 and content of antimony ranging from 0.25 g·kg^-1 up to 12 g·kg^-1. Next-generation sequencing approach with 16S RNA, 18S RNA and ITS markers was used to characterize bacterial, fungal, algal, metazoal and protozoal communities occurring in the HFOs. In the 16S RNA, the analysis dominated bacteria (96.2%) were mainly Proteobacteria (68.8%) and Bacteroidetes (10.2%) and to less extent also Acidobacteria, Actinobacteria, Cyanobacteria, Firmicutes, Nitrosprae and Chloroflexi. Alpha and beta diversity analysis revealed that the bacterial communities of individual sites do not differ significantly, and only subtle seasonal changes were observed. In this As and Sb rich, circumneutral microenvironment, rich in iron, sulfates and carbonates, methylotrophic bacteria (Methylobacter, Methylotenera), metal/reducing bacteria (Geobacter, Rhodoferax), metal-oxidizing and denitrifying bacteria (Gallionella, Azospira, Sphingopyxis, Leptothrix and Dechloromonas), sulfur-oxidizing bacteria (Sulfuricurvum, Desulphobulbaceae) and nitrifying bacteria (Nitrospira, Nitrosospira) accounted for the most dominant ecological groups and their impact over Fe, As, Sb, sulfur and nitrogen geocycles is discussed. This study provides evidence of diverse microbial communities that exist in drainage waters and are highly important in the process of mobilization or immobilization of the potentially toxic elements.

Variable response of arsenic contaminated groundwater microbial community to electron acceptor regime revealed by microcosm based high-throughput sequencing approach

Arsenic (As) mobilization in alluvial aquifers is facilitated by microbially catalyzed redox transformations that depend on the availability of electron acceptors (EAs). In this study, the response of an As-contaminated groundwater microbial community from West Bengal, India towards varied EAs was elucidated through microcosm based 16S rRNA gene amplicon sequencing. Acinetobacter, Deinococcus, Nocardioides, etc., and several unclassified bacteria (Ignavibacteria) and archaea (Bathyarchaeia, Micrarchaeia) previously not reported from As-contaminated groundwater of West Bengal, characterized the groundwater community. Distinct shifts in community composition were observed in response to various EAs. Enrichment of operational taxonomic units (OTUs) affiliated to Denitratisoma (NO₃-), Spirochaetaceae (Mn⁴⁺), Deinococcus (As⁵⁺), Ruminiclostridium (Fe³⁺), Macellibacteroides (SO₄²-), Holophagae-Subgroup 7 (HCO₃-), Dechloromonas and Geobacter (EA mixture) was noted. Alternatively, As³⁺ amendment as electron donor allowed predominance of Rhizobium. Taxonomy based functional profiling highlighted the role of chemoorganoheterotrophs capable of concurrent reduction of NO₃-, Fe³⁺, SO₄²-, and As biotransformation in As-contaminated groundwater of West Bengal. Our analysis revealed two major aspects of the community, (a) taxa selective toward responding to the EAs, and (b) multifaceted nature of taxa appearing in abundance in response to multiple substrates. Thus, the results emphasized the potential of microbial community members to influence the biogeochemical cycling of As and other dominant anions/cations.

Geochemical, metagenomic, and physiological characterization of the multifaceted interaction between microbiome of an arsenic contaminated groundwater and aquifer sediment

Geomicrobiological details of the interactions between groundwater microbiome (GWM) and arsenic (As)-rich aquifer sediment of Bengal basin was investigated through microcosm incubations. Role of key microorganisms and their specific interactions with As-bearing minerals was demarcated under organic carbon- amended and -unamended conditions. Acinetobacter (50.8 %), Brevundimonas (7.9 %), Sideroxydans (3.4 %), Alkanindiges (3.0 %) dominated the GWM. The microbiome catalysed considerable alterations in As-bearing mineral [Fe-(hydr)oxide and aluminosilicate] phases resulting in substantial changes in overall geochemistry and release of As (65 μg/L) and Fe (118 μg/L). Synergistic roles of autotrophic, NH₄⁺-oxidizing Archaea (Thaumarchaeota) and chemoheterotrophic bacteria (Stenotrophomonas, Pseudomonas, Geobacter) of diverse metabolic abilities (NH₄⁺-oxidizing, NO₃^-, As/Fe-reducing) were noted for observed changes. Organic carbon supported enhanced microbial growth and As mobilization (upto 403.2 μg As/L) from multiple mineral phases (hematite, magnetite, maghemite, biotite, etc.). In presence of high organic carbon, concerted actions of anaerobic, hydrocarbon-utilizing, As-, Fe-reducing Rhizobium, fermentative Escherichia, anaerobic Bacillales, metal-reducing and organic acid-utilizing Pseudomonas and Achromobacter were implicated in altering sediment mineralogy and biogeochemistry. Increase in abundance of arrA, arsC, bssA genes, and dissolution of Fe, Ca, Mg, Mn confirmed that dissimilatory-, cytosolic-As reduction, and mineral weathering fuelled by anaerobic (hydro)carbon metabolism are the predominant mechanisms of As release in aquifers of Bengal basin.

Adaptation of Microbial Communities to Environmental Arsenic and Selection of Arsenite-Oxidizing Bacteria From Contaminated Groundwaters

Arsenic mobilization in groundwater systems is driven by a variety of functionally diverse microorganisms and complex interconnections between different physicochemical factors. In order to unravel this great ecosystem complexity, groundwaters with varying background concentrations and speciation of arsenic were considered in the Po Plain (Northern Italy), one of the most populated areas in Europe affected by metalloid contamination. High-throughput Illumina 16S rRNA gene sequencing, CARD-FISH and enrichment of arsenic-transforming consortia showed that among the analyzed groundwaters, diverse microbial communities were present, both in terms of diversity and functionality. Oxidized inorganic arsenic [arsenite, As(III)] was the main driver that shaped each community. Several uncharacterized members of the genus Pseudomonas, putatively involved in metalloid transformation, were revealed in situ in the most contaminated samples. With a cultivation approach, arsenic metabolisms potentially active at the site were evidenced. In chemolithoautotrophic conditions, As(III) oxidation rate linearly correlated to As(III) concentration measured at the parental sites, suggesting that local As(III) concentration was a relevant factor that selected for As(III)-oxidizing bacterial populations. In view of the exploitation of these As(III)-oxidizing consortia in biotechnology-based arsenic bioremediation actions, these results suggest that contaminated aquifers in Northern Italy host unexplored microbial populations that provide essential ecosystem services.

Metagenome-assembled genome distribution and key functionality highlight importance of aerobic metabolism in Svalbard permafrost

Permafrost underlies a large portion of the land in the Northern Hemisphere. It is proposed to be an extreme habitat and home for cold-adaptive microbial communities. Upon thaw permafrost is predicted to exacerbate increasing global temperature trend, where awakening microbes decompose millennia old carbon stocks. Yet our knowledge on composition, functional potential and variance of permafrost microbiome remains limited. In this study, we conducted a deep comparative metagenomic analysis through a 2 m permafrost core from Svalbard, Norway to determine key permafrost microbiome in this climate sensitive island ecosystem. To do so, we developed comparative metagenomics methods on metagenomic-assembled genomes (MAG). We found that community composition in Svalbard soil horizons shifted markedly with depth: the dominant phylum switched from Acidobacteria and Proteobacteria in top soils (active layer) to Actinobacteria, Bacteroidetes, Chloroflexi and Proteobacteria in permafrost layers. Key metabolic potential propagated through permafrost depths revealed aerobic respiration and soil organic matter decomposition as key metabolic traits. We also found that Svalbard MAGs were enriched in genes involved in regulation of ammonium, sulfur and phosphate. Here, we provide a new perspective on how permafrost microbiome is shaped to acquire resources in competitive and limited resource conditions of deep Svalbard soils.

Understanding the mechanistic insight of arsenic exposure and decoding the histone cipher

BACKGROUND

The study of heritable epigenetic changes in arsenic exposure has intensified over the last decade. Groundwater arsenic contamination causes a great threat to humans and, to date, no accurate measure has been formulated for remediation. The fascinating possibilities of epi-therapeutics identify the need for an in-depth mechanistic understanding of the epigenetic landscape.

OBJECTIVE

In this comprehensive review, we have set to analyze major studies pertaining to histone post-translational modifications in arsenic-mediated disease development and carcinogenesis during last ten years (2008-2018).

RESULTS

The role of the specific histone marks in arsenic toxicity has been detailed. A comprehensive list that includes major arsenic-induced histone modifications identified for the last 10 years has been documented and details of different states of arsenic, organisms, exposure type, study platform, and findings were provided. An arsenic signature panel was suggested to help in early prognosis. An attempt has been made to identify the grey areas of research.

PROSPECTS

Future prospective multi-target analyses of the inter-molecular crosstalk among different histone marks are needed to be explored further in order to understand the mechanism of arsenic toxicity and carcinogenicity and to confirm the suitability of these epi-marks as prognostic markers.