Arsenic Metabolism Research Articles

AsgeneDB: a curated orthology arsenic metabolism gene database and computational tool for metagenome annotation.

Arsenic (As) is the most ubiquitous toxic metalloid in nature. Microbe-mediated As metabolism plays an important role in global As biogeochemical processes, greatly changing its toxicity and bioavailability. While metagenomic sequencing may advance our understanding of the As metabolism capacity of microbial communities in different environments, accurate metagenomic profiling of As metabolism remains challenging due to low coverage and inaccurate definitions of As metabolism gene families in public orthology databases. Here we developed a manually curated As metabolism gene database (AsgeneDB) comprising 400 242 representative sequences from 59 As metabolism gene families, which are affiliated with 1653 microbial genera from 46 phyla. AsgeneDB achieved 100% annotation sensitivity and 99.96% annotation accuracy for an artificial gene dataset. We then applied AsgeneDB for functional and taxonomic profiling of As metabolism in metagenomes from various habitats (freshwater, hot spring, marine sediment and soil). The results showed that AsgeneDB substantially improved the mapping ratio of short reads in metagenomes from various environments. Compared with other databases, AsgeneDB provides more accurate, more comprehensive and faster analysis of As metabolic genes. In addition, we developed an R package, Asgene, to facilitate the analysis of metagenome sequencing data. Therefore, AsgeneDB and the associated Asgene package will greatly promote the study of As metabolism in microbial communities in various environments.

Evaluation of low-to-moderate arsenic exposure, metabolism and skin lesions in a Turkish rural population exposed through drinking water.

There is no human data regarding the exposure, metabolism and potential health effects of arsenic (As) contamination in drinking water in the Central Anatolian region of Turkey. Residents in ten villages with drinking water of total As (T-As) level >50μg L-1 and 10-50μg L-1 were selected as an exposed group (n=420) and <10μg L-1 as an unexposed group (n=185). Time-weighted average-As (TWA-As) intake was calculated from T-As analysis of drinking water samples. Concentrations of T-As in urine and hair samples, urinary As species [i.e., As(III), As(V), MMA(V) and DMA(V], and some micronutrients in serum samples of residents of the study area were determined. Primary and secondary methylation indices (PMI and SMI, respectively) were assessed from urinary As species concentrations and the presence of skin lesion was examined. TWA-As intake was found as 75μg L-1 in the exposed group. Urinary and hair T-As and urinary As species concentrations were significantly higher in the exposed group (P<0.05). The PMI and SMI values revealed that methylation capacities of the residents were efficient and that there was no saturation in As metabolism. No significant increase was observed in the frequency of skin lesions (hyperpigmentation, hypopigmentation, keratosis) of the exposed group (P>0.05). Only frequency of keratosis either at the hand or foot was higher in individuals with hair As concentration >1μg g-1 (P<0.05). Individuals living in the study area were chronically exposed to low-to-moderate As due to geological contamination in drinking water. No significant increase was observed in the frequency of skin lesions. Because of the controversy surrounding the health risks of low-to-moderate As exposure, it is critical to initiate long-term follow-up studies on health effects in this region.

Arsenic Metabolism, Toxicity and Accumulation in the White Button Mushroom Agaricus bisporus.

Mushrooms have unique properties in arsenic metabolism. In many commercial and wild-grown mushrooms, arsenobetaine (AsB), a non-toxic arsenical, was found as the dominant arsenic species. The AsB biosynthesis remains unknown, so we designed experiments to study conditions for AsB formation in the white button mushroom, Agaricus bisporus. The mushrooms were treated with various arsenic species including arsenite (As(III)), arsenate (As(V)), methylarsenate (MAs(V)), dimethylarsenate (DMAs(V)) and trimethylarsine oxide (TMAsO), and their accumulation and metabolism were determined using inductively coupled mass spectrometer (ICP-MS) and high-pressure liquid chromatography coupled with ICP-MS (HPLC-ICP-MS), respectively. Our results showed that mycelia have a higher accumulation for inorganic arsenicals while fruiting bodies showed higher accumulation for methylated arsenic species. Two major arsenic metabolites were produced in fruiting bodies: DMAs(V) and AsB. Among tested arsenicals, only MAs(V) was methylated to DMAs(V). Surprisingly, AsB was only detected as the major arsenic product when TMAsO was supplied. Additionally, AsB was only detected in the fruiting body, but not mycelium, suggesting that methylated products were transported to the fruiting body for arsenobetaine formation. Overall, our results support that methylation and AsB formation are two connected pathways where trimethylated arsenic is the optimal precursor for AsB formation.

Contribution of gut bacteria to arsenic metabolism in the first year of life in a prospective birth cohort

Contribution of gut bacteria to arsenic metabolism in the first year of life in a prospective birth cohort

Urinary biomarkers of inorganic arsenic exposure, inorganic arsenic metabolism, and birth weight in Tacna, Peru, 2019

Urinary biomarkers of inorganic arsenic exposure, inorganic arsenic metabolism, and birth weight in Tacna, Peru, 2019

Changes in arsenic accumulation and metabolic capacity after environmental management measures in mining area

Due to the public health concern of arsenic, environmental management measures in mining areas had been implemented. To assess the effect of environmental management measures in the mining area comprehensively, arsenic accumulation in the urine, hair, nails, and urinary metabolites of residents in a realgar mining area in Hunan province, China were investigated in 2019, and the changes in arsenic levels in the biomarkers during 2012–2019 were tracked. The importance of confounding factors (age, sex, occupation, residence, clinical history, vegetable source, cooking fuel, smoking, alcohol consumption, BMI) was analyzed using the Boruta algorithm. After the implementation of environmental management measures (including ceasing mining and smelting activities, building landfills, adjusting the planting structure, and soil restoration), urine, hair, and nail arsenic concentration decreased drastically but were still excessive. Arsenic accumulation was highest in older male miners who were long settled in the mining area and consumed homegrown vegetables. The only factor for changes in urinary arsenic levels was the cooking fuel type; residents using wood as cooking fuel experienced sustained arsenic exposure. Occupation and sex were important for determining arsenic changes in the hair and nails. Short-term arsenic accumulation in urine was affected by arsenic exposure, while long-term accumulation in hair and nails by arsenic metabolic capacity. The percentage of urinary arsenic metabolism and arsenic methylation indices of the participants in the mining area were within the normal range (%iAs: 10–30 %, %MMA: 10–20 %, % DMA: 60–80 %); samples indicated worse metabolic capacity than the reference population. The arsenic metabolic capacity of male miners was relatively weak, probably aggravated by alcohol drinking and smoking. Without soil remediation, arsenic exposure will continue. Homegrown vegetables and biomass fuels should be abandoned; reduced cigarette and alcohol consumption is recommended. Urinary arsenic would be more proper for assessing environmental remediation in mining areas.

The Duality of Arsenic Metabolism: Impact on Human Health.

Arsenic is a naturally occurring hazardous element that is environmentally ubiquitous in various chemical forms. Upon exposure, the human body initiates an elimination pathway of progressive methylation into relatively less bioreactive and more easily excretable pentavalent methylated forms. Given its association with decreasing the internal burden of arsenic with ensuing attenuation of its related toxicities, biomethylation has been applauded for decades as a pure route of arsenic detoxification. However, the emergence of detectable trivalent species with profound toxicity has opened a long-standing debate regarding whether arsenic methylation is a detoxifying or bioactivating mechanism. In this review, we approach the topic of arsenic metabolism from both perspectives to create a complete picture of its potential role in the mitigation or aggravation of various arsenic-related pathologies.

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

Microorganisms are essential for modifying arsenic morphology, mobility, and toxicity. Still, knowledge of the microorganisms responsible for arsenic metabolism in specific arsenic-contaminated fields, such as metallurgical plants is limited. We sampled on-field soils from three depths at 70 day intervals to explore the distribution and transformation of arsenic in the soil. Arsenic-metabolizing microorganisms were identified from the mapped gene sequences. Arsenic metabolism pathways were constructed with metagenomics and AsChip analysis (a high-throughput qPCR chip for arsenic metabolism genes). It has been shown in the result that 350 genera of arsenic-metabolizing microorganisms carrying 17 arsenic metabolism genes in field soils were identified, as relevant to arsenic reduction, arsenic methylation, arsenic respiration, and arsenic oxidation, respectively. Arsenic reduction genes were the only genes shared by the 10 high-ranking arsenic-metabolizing microorganisms. Arsenic reduction genes (arsABCDRT and acr3) accounted for 73.47%–78.11% of all arsenic metabolism genes. Such genes dominated arsenic metabolism, mediating the reduction of 14.11%–19.86% of As(V) to As(III) in 0–100 cm soils. Arsenic reduction disrupts microbial energy metabolism, DNA replication and repair and membrane transport. Arsenic reduction led to a significant decrease in the abundance of 17 arsenic metabolism genes (p < 0.0001). The critical role of arsenic-reducing microorganisms in the migration and transformation of arsenic in metallurgical field soils, was emphasized with such results. These results were of pronounced significance for understanding the transformation behavior of arsenic and the precise regulation of arsenic in field soil.

Metabolism of Arsenic in Human by AS3MT Gene

The AS3MT may be the most significant protein for the methylation of chemical elements species. The transfer of methyl radical from S-adenosyl-L-methionine (AdoMet) to powerfulness arsenical (AsIII) is catalyzed by the AS3MT that is critical for arsenic metabolism in humans. Since the AS3MT genetic polymorphism is linked to arsenic resistance, the association between the single ester polymorphism (SNP) and AS3MT inorganic arsenic (iAs) metabolism is being studied. Additionally, we tend to compared chemical action properties of recombinant human AS3MT and AS3MT/M287T. In reaction S-adenosylmethionine, arsenite, or methylarsonous acid (MAsIII) as substrates and endogenous reductants, together with glutathione (GSH), a thioredoxin enzyme (TR) system and tris(2-carboxyethyl) pesticide complex (TCEP). By victimization of either TR or Trx or NADPH or TCEP, AS3MT catalyzes the conversion of iAsIII to MAsIII then to methyl radical sonic acid (MAsV), dimethylarsinous acid (DMAsIII), and diethylarsinic acid (DMAsV). The Cys156 and Cys206 gift in similarity model forms the binding website for AsIII. Cys32 and Cys61 are linked by disulphidebond. The most important product in the initiative of methylation is MAsIII which remains sure to protein until it gets methylated. The product is a lot of hepatotoxic and more malignant neoplastic disease powerfulness methyl arsenicals, however, arsenic undergoes oxidation and reduction as enzyme-bound intermediates.

Contribution of gut bacteria to arsenic metabolism in the first year of life in a prospective birth cohort

Gut bacteria are at the interface of environmental exposures and their impact on human systems, and may alter host absorption, metabolism, and excretion of toxic chemicals. We investigated whether arsenic-metabolizing bacterial gene pathways related to urinary arsenic concentrations. In the New Hampshire Birth Cohort Study, urine and stool samples were obtained at six weeks (n = 186) and one year (n = 190) of age. Inorganic arsenic (iAs), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), and arsenobetaine (AsB) were quantified in infant urine samples using high-performance liquid chromatography with inductively coupled plasma mass spectrometry. Total arsenic exposure (tAs) was summarized as Σ(iAs, MMA, DMA) and log2-transformed. Fecal microbial DNA underwent metagenomic sequencing and the relative abundance of bacterial gene pathways were grouped as KEGG Orthologies (KOs) using BioBakery algorithms. Arsenic metabolism KOs with >80% prevalence were log2-transformed and modeled continuously using linear regression, those with <10% were not evaluated and those with 10–80% prevalence were analyzed dichotomously (detect/non-detect) using logistic regression. In the first set of models, tAs was regressed against KO relative abundance or detection adjusting for age at sample collection and child's sex. Effect modification by delivery mode was assessed in stratified models. In the second set of models, the association between the relative abundance/detection of the KOs and arsenic speciation (%iAs, %MMA, %DMA) was quantified with linear regression. Urinary tAs was associated with the increased relative abundance/detection odds of several arsenic-related KOs, including K16509, an arsenate reductase transcriptional regulator, with stronger associations among six-week-olds than one-year-olds. K16509 was also associated with decreased %MMA and increased %DMA at six weeks and one year. Notably, many associations were stronger among operatively-delivered than vaginally-delivered infants. Our findings suggest associations between arsenic-metabolizing bacteria in the infant gut microbiome and urinary arsenic excretion.

Human adaptation to arsenic in Bolivians living in the Andes.

Humans living in the Andes Mountains have been historically exposed to arsenic from natural sources, including drinking water. Enzymatic methylation of arsenic allows it to be excreted more efficiently by the human body. Adaptation to high-arsenic environments via enhanced methylation and excretion of arsenic was first reported in indigenous women in the Argentinean Andes, but whether adaptation to arsenic is a general phenomenon across native populations from the Andes Mountains remains unclear. Therefore, we evaluated whether adaptation to arsenic has occurred in the Bolivian Andes by studying indigenous groups who belong to the Aymara-Quechua and Uru ethnicities and have lived in the Bolivian Andes for generations. Our population genetics methods, including genome-wide selection scans based on linkage disequilibrium patterns and allele frequency differences, in combination with targeted and whole-genome sequencing and genotype-phenotype association analyses, detected signatures of positive selection near the gene encoding arsenite methyltransferase (AS3MT), the main arsenic methylating enzyme. This was among the strongest selection signals (top 0.5% signals via locus-specific branch length and extended haplotype homozygosity tests) at a genome-wide level in the Bolivian study groups. We found a large haplotype block of 676kb in the AS3MT region and identified candidate functional variants for further analysis. Moreover, our analyses revealed associations between AS3MT variants and the fraction of mono-methylated arsenic in urine and showed that the Bolivian study groups had the highest frequency of alleles associated with more efficient arsenic metabolism reported so far. Our data support the idea that arsenic exposure has been a driver for human adaptation to tolerate arsenic through more efficient arsenic detoxification in different Andean populations.

Gut Microbiome and Health Assessment Due To Arsenic Toxicity: A Review

Arsenic is considered as a class 1 carcinogen and first among toxicants ranked by the Environmental Protection Agency. Arsenic toxicity includes deleterious effect on gut microbiota, gastrointestinal disorder, immunological disturbances, disrupting metabolism and compromising the host health. Over 103–104 microorganisms with possibly 500 to 1,000 different species inhabit within the gut with 150 times more genes than the human genome. They help to digest food and play an essential role in our well- being. Gut microbiota affects our whole metabolism as well as the immune system of the host. Arsenic induced toxicity is a major health challenge leading to many neurological and immunological problems and inhibits the growth of many bacterial species common in the gastrointestinal tract. The Gut microbiome carries multiple functions that are beneficial to the hosts. Arsenic exposure will be a critical concern for human health. Human gut microbiomes may be biochemically responsible for arsenic metabolism, change in the arsenic compounds and several arsenical transformations that may lead to arsenic toxicity. Arsenic metabolism occurs in the liver by arsenic methyltransferase (AS3MT) which methylates it into the inorganic arsenic, and ultimately eliminated through urine. Recent studies showed that biotransformation of gut microbiome causes alteration of microbiome morphology and physiology that may alter the ArsBC gene activity due to arsenic toxicity. We aimed at summarising that arsenic induced perturbed gut microbiome communities that trigger systemic responses in diverse organs. Due to gut microbiota perturbation, changes in gut permeability and metabolism have been identified, and there is a shift in the population of gut bacterial species having arsenic resistant genes that result in disturbance of host metabolic homeostasis. Here we review known aspects of arsenic gut microbes' interaction, this will help to understand about arsenic toxicity with the gut microbiome and their deleterious effects.

Virioplankton assemblages from challenger deep, the deepest place in the oceans

SummaryHadal ocean biosphere, that is, the deepest part of the world’s oceans, harbors a unique microbial community, suggesting a potential uncovered co-occurring virioplankton assemblage. Herein, we reveal the unique virioplankton assemblages of the Challenger Deep, comprising 95,813 non-redundant viral contigs from the surface to the hadal zone. Almost all of the dominant viral contigs in the hadal zone were unclassified, potentially related to Alteromonadales and Oceanospirillales. 2,586 viral auxiliary metabolic genes from 132 different KEGG orthologous groups were mainly related to the carbon, nitrogen, sulfur, and arsenic metabolism. Lysogenic viral production and integrase genes were augmented in the hadal zone, suggesting the prevalence of viral lysogenic life strategy. Abundant rve genes in the hadal zone, which function as transposase in the caudoviruses, further suggest the prevalence of viral-mediated horizontal gene transfer. This study provides fundamental insights into the virioplankton assemblages of the hadal zone, reinforcing the necessity of incorporating virioplankton into the hadal biogeochemical cycles.

Abstract 1440: Identifying inherited genetic variation that impacts individuals’ ability to metabolize arsenic and susceptibility to toxicity

Abstract Inorganic arsenic (iAs) is a class I human carcinogen, and exposure to iAs affects &amp;gt;200 million individuals worldwide. In Bangladesh, &amp;gt;57 million individuals are chronically exposed to iAs through drinking-water. There is inter-individual variation in arsenic metabolism efficiency (AME) due to inherited genetic variation, and this variability impacts individuals’ internal dose of arsenic and their susceptibility to toxicity. Identifying genetic determinants of AME to help identify individuals at higher risk for toxicity has been a focus within genetic epidemiology research. Consumed arsenic enters the blood in as iAs. Sequential reduction and methylation reactions are catalyzed by glutathione and arsenic methyltransferase (AS3MT) respectively, producing monomethylated (MMA) and dimethylated (DMA) forms of arsenic. Generation of DMA is beneficial because DMA is more easily expelled from the body in urine compared to MMA or iAs. AME is often represented by the percent of the arsenic species in urine that exists as DMA. Previous studies have identified genetic variants in the AS3MT (10q24.32) and FTCD (21q22.3) regions as showing clear association with AME. However, additional regions containing variants showing robust and replicable association with AME have not yet been identified, although studies of AME heritability suggest that additional variants are likely to exist. We used data from &amp;gt;7,000 participants from two studies of Bangladesh individuals with varying levels of exposure to arsenic through drinking water (The Health Effects of Arsenic Longitudinal Study, HEALS, and the Bangladesh Vitamin E and Selenium Trial, BEST) to identify genetic variation that impacts individuals’ ability to metabolize arsenic and their susceptibility to toxicity (i.e., arsenic-induced skin lesions). Our preliminary results suggest novel associations with AME in the 1q24.3 region (p= 5.16 x10-14) and with skin lesion risk in the 6p21.33 region (p=1.37x10-9). The identified variants in the 1q24.3 region reside in and around the FMO3 gene. FMOs are enzymes involved in xenobiotic metabolism; therefore, it is plausible that they may play a role in arsenic metabolism. The 6p21.33 signal is in the major histocompatibility complex (MHC) region, which contains numerous key immune response genes (e.g., HLA genes). These results suggest the existence of additional variants associated with AME and arsenic toxicity risk. Citation Format: Lizeth I. Tamayo, Lin Tong, Muhammad G. Kibriya, Farzana Jasmine, Habibul Ahsan, Brandon L. Pierce. Identifying inherited genetic variation that impacts individuals’ ability to metabolize arsenic and susceptibility to toxicity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1440.

Sulfur reduces arsenic accumulation in rice shoot by enhancing root retention and altering arsenic metabolism

Rice can potentially pose serious health risks due to its higher arsenic (As) uptake. Sulfur (S) is not only an essential macronutrient, but it also has the ability to decrease As accumulation. In the present study, a hydroponic experiment was conducted to investigate the mechanisms underlying the effects of S on the As uptake and transport at different S (pre-)treatments and additional supply levels. It was found that additional S supply decreased As content by 20%–50% in both S-deficient and S-normal pre-treated shoots compared to the no S supply throughout the treatment; As root-to-shoot translocation factors was reduced by 7%–46% with S supply. On the one hand, additional S supply could elevate levels of thiol compounds (by 15%–280%) and increase the As percentage in soluble cytosol of roots. Additional S supply also enhanced the casparian strip development of rice roots, which could block As transfer in roots apoplast pathway. Moreover, additional S supply lead to the down-regulation of OsLsi2 expression (e.g., reduced by 71% by S at 2 mmol L−1 with the S-normal pre-treatment). Sulfur also promoted the biotransformation of As(III) in shoots into less toxic As species; reducing the As(III) proportion by 25% by 2 mmol L−1 of S under S-normal pre-treatment. These results suggest that S could play an important role in the inhibition of As transfer and the detoxification of As in rice by enhancing root retention (the vacuole sequestration), impeding transportation pathway of root apoplast, and regulating As-related gene expression. Thus, providing a basis for the potential application of S in rice production in As-contaminated paddy soil.

Characterization of Two Highly Arsenic-Resistant Caulobacteraceae Strains of Brevundimonas nasdae: Discovery of a New Arsenic Resistance Determinant.

Arsenic (As), distributed widely in the natural environment, is a toxic substance which can severely impair the normal functions in living cells. Research on the genetic determinants conferring functions in arsenic resistance and metabolism is of great importance for remediating arsenic-contaminated environments. Many organisms, including bacteria, have developed various strategies to tolerate arsenic, by either detoxifying this harmful element or utilizing it for energy generation. More and more new arsenic resistance (ars) determinants have been identified to be conferring resistance to diverse arsenic compounds and encoded in ars operons. There is a hazard in mobilizing arsenic during gold-mining activities due to gold- and arsenic-bearing minerals coexisting. In this study, we isolated 8 gold enrichment strains from the Zijin gold and copper mine (Longyan, Fujian Province, China) wastewater treatment site soil, at an altitude of 192 m. We identified two Brevundimonas nasdae strains, Au-Bre29 and Au-Bre30, among these eight strains, having a high minimum inhibitory concentration (MIC) for As(III). These two strains contained the same ars operons but displayed differences regarding secretion of extra-polymeric substances (EPS) upon arsenite (As(III)) stress. B. nasdae Au-Bre29 contained one extra plasmid but without harboring any additional ars genes compared to B. nasdae Au-Bre30. We optimized the growth conditions for strains Au-Bre29 and Au-Bre30. Au-Bre30 was able to tolerate both a lower pH and slightly higher concentrations of NaCl. We also identified folE, a folate synthesis gene, in the ars operon of these two strains. In most organisms, folate synthesis begins with a FolE (GTP-Cyclohydrolase I)-type enzyme, and the corresponding gene is typically designated folE (in bacteria) or gch1 (in mammals). Heterologous expression of folE, cloned from B. nasdae Au-Bre30, in the arsenic-hypersensitive strain Escherichia coli AW3110, conferred resistance to As(III), arsenate (As(V)), trivalent roxarsone (Rox(III)), pentavalent roxarsone (Rox(V)), trivalent antimonite (Sb(III)), and pentavalent antimonate (Sb(V)), indicating that folate biosynthesis is a target of arsenite toxicity and increased production of folate confers increased resistance to oxyanions. Genes encoding Acr3 and ArsH were shown to confer resistance to As(III), Rox(III), Sb(III), and Sb(V), and ArsH also conferred resistance to As(V). Acr3 did not confer resistance to As(V) and Rox(V), while ArsH did not confer resistance to Rox(V).

A comparative study indicates vertical inheritance and horizontal gene transfer of arsenic resistance-related genes in eukaryotes

Arsenic is a ubiquitous element in the environment, a source of constant evolutionary pressure on organisms. The arsenic resistance machinery is thoroughly described for bacteria. Highly resistant lineages are also common in eukaryotes, but evolutionary knowledge is much more limited. While the origin of the resistance machinery in eukaryotes is loosely attributed to horizontal gene transfer (HGT) from bacteria, only a handful of eukaryotes were deeply studied. Here we investigate the origin and evolution of the core genes in arsenic resistance in eukaryotes using a broad phylogenetic framework. We hypothesize that, as arsenic pressure is constant throughout Earth’s history, resistance mechanisms are probably ancestral to eukaryotes. We identified homologs for each of the arsenic resistance genes in eukaryotes and traced their possible origin using phylogenetic reconstruction. We reveal that: i. an important component of the arsenic-resistant machinery originated before the last eukaryotic common ancestor; ii. later events of gene duplication and HGT generated new homologs that, in many cases, replaced ancestral ones. Even though HGT has an important contribution to the expansion of arsenic metabolism in eukaryotes, we propose the hypothesis of ancestral origin and differential retention of arsenic resistance mechanisms in the group. Key-words: Environmental adaptation; resistance to toxic metalloids; detoxification; comparative genomics; functional phylogenomics.

Transcriptomic underpinnings of high and low mirror aggression zebrafish behaviours

BackgroundAggression is an adaptive behaviour that animals use to protect offspring, defend themselves and obtain resources. Zebrafish, like many other animals, are not able to recognize themselves in the mirror and typically respond to their own reflection with aggression. However, mirror aggression is not an all-or-nothing phenomenon, with some individuals displaying high levels of aggression against their mirror image, while others show none at all. In the current work, we have investigated the genetic basis of mirror aggression by using a classic forward genetics approach - selective breeding for high and low mirror aggression zebrafish (HAZ and LAZ).ResultsWe characterized AB wild-type zebrafish for their response to the mirror image. Both aggressive and non-aggressive fish were inbred over several generations. We found that HAZ were on average more aggressive than the corresponding LAZ across generations and that the most aggressive adult HAZ were less anxious than the least aggressive adult LAZ after prolonged selective breeding. RNAseq analysis of these fish revealed that hundreds of protein-encoding genes with important diverse biological functions such as arsenic metabolism (as3mt), cell migration (arl4ab), immune system activity (ptgr1), actin cytoskeletal remodelling (wdr1), corticogenesis (dgcr2), protein dephosphorylation (ublcp1), sialic acid metabolism (st6galnac3) and ketone body metabolism (aacs) were differentially expressed between HAZ and LAZ, suggesting a strong genetic contribution to this phenotype. DAVID pathway analysis showed that a number of diverse pathways are enriched in HAZ over LAZ including pathways related to immune function, oxidation-reduction processes and cell signalling. In addition, weighted gene co-expression network analysis (WGCNA) identified 12 modules of highly correlated genes that were significantly associated with aggression duration and/or experimental group.ConclusionsThe current study shows that selective breeding based of the mirror aggression phenotype induces strong, heritable changes in behaviour and gene expression within the brain of zebrafish suggesting a strong genetic basis for this behaviour. Our transcriptomic analysis of fish selectively bred for high and low levels of mirror aggression revealed specific transcriptomic signatures induced by selective breeding and mirror aggression and thus provides a large and novel resource of candidate genes for future study.

Bacterial Arsenic Metabolism and Its Role in Arsenic Bioremediation.

Arsenic contaminations, often adversely influencing the living organisms, including plants, animals, and the microbial communities, are of grave apprehension. Many physical, chemical, and biological techniques are now being explored to minimize the adverse affects of arsenic toxicity. Bioremediation of arsenic species using arsenic loving bacteria has drawn much attention. Arsenate and arsenite are mostly uptaken by bacteria through aquaglycoporins and phosphate transporters. After entering arsenic inside bacterial cellarsenic get metabolized (e.g.,reduction, oxidation, methylation, etc.) into different forms. Arsenite is sequentially methylated into monomethyl arsenic acid (MMA) and dimethyl arsenic acid (DMA), followed by a transformation of less toxic, volatile trimethyl arsenic acid (TMA). Passive remediation techniques, including adsorption, biomineralization, bioaccumulation, bioleaching, and so on are exploited by bacteria. Rhizospheric bacterial association with some specific plants enhances phytoextraction process. Arsenic-resistant rhizospheric bacteria have immense role in enhancement of crop plant growth and development, but their applications are not well studied till date. Emerging techniques like phytosuction separation (PS-S) have a promising future, but still light to be focused on these techniques. Plant-associated bioremediation processes like phytoextraction and phytosuction separation (PS-S) techniques might be modified by treating with potent bacteria for furtherance.

Gender difference in arsenic biotransformation is an important metabolic basis for arsenic toxicity

BackgroundArsenic metabolism enzymes can affect the toxic effects of arsenic. However, the effects of different genders on the metabolites and metabolic enzymes in liver arsenic metabolism is still unclear. This study analyzed the gender differences of various arsenic metabolites and metabolic enzymes and further explored the effects of gender differences on arsenic metabolism in liver tissues of rats.MethodsRats were treated with high/medium/low doses of iAs3+ or iAs5+. Liver pathological changes were observed with electron microscopy. The monomethyl aracid (MMA) and dimethyl aracid (DMA) was determined by high performance liquid chromatography-hydride generation atomic fluorescence spectroscopy. S-adenosylmethionine (SAM), arsenate respiratory reductase (ARR), nicotinamide adenine dinucleotide (NAD), purine nucleoside phosphorylase (PNP), pyruvate kinase (PK), and myeloperoxidase (MPO) SAM, ARR, NAD, PNP, PK, and MPO were determined by enzyme-linked immunoassay. RT-qPCR was used to determine Arsenic (+ 3 oxidation state) methyltransferase (AS3MT).ResultsThe iAs3+ and iAs5+ at high doses induced pathological changes in the liver, such as increased heterochromatin and lipid droplets. Compared within the same group, MMA and DMA were statistically significant in iAs3 + high, iAs3 + medium and iAs5+ low dose groups (P < 0.05). MMA of male rats in iAs3+ high and medium groups was higher than that of female rats, and the DMA of male rats was lower than that of female rats. As3MT mRNA in the male iAs3+ high group was higher than that of females. Besides, compared between male and female, only in iAS3+ low dose, iAS3+ medium dose, iAS5+ low dose, and iAS5+ medium dose groups, there was significant difference in SAM level (P < 0.05). Compared within the same group, male rats had significantly higher PNP and ARR activities while lower PK activity than female rats (P < 0.05). Between the male and female groups, only the iAS3+ high dose and medium dose group had a statistically significant difference (P < 0.05). The NAD activity of females in iAS3+ high dose group was higher than that of males.ConclusionThe gender differences in the arsenic metabolism enzymes may affect the biotransformation of arsenic, which may be one of the important mechanisms of arsenic toxicity of different sexes and different target organs.