High Metal Concentrations Research Articles

Isolation and identification of metallotolerant bacteria with a potential biotechnological application

Mining has led to severe environmental pollution in countries with exhaustive mining production and inadequate industrial waste regulation. Microorganisms in contaminated sites, like mine tailings, have adapted to high concentrations of heavy metals, developing the capacity of reducing or removing them from these environments. Therefore, it is essential to thoroughly characterize bacteria present in these sites to find different ways of bioremediation. In this regard, in this study, an enrichment and isolation procedure were performed to isolate bacteria with lower nutritional requirements and high tolerance to Cu(II) and Fe(II) from two Sonoran River basin mining tails. Two Staphylococcus species and a Microbacterium ginsengisoli strain were isolated and identified from the San Felipe de Jesús mining tail. Also, three strains were isolated from the Nacozari de García mining tail: Burkholderia cenocepacia, Sphingomonas sp. and Staphylococcus warneri. Significant microbiological differences were found between the two sites. All these species exhibited tolerance up to 300 mg/L for Cu (II)–Fe (II) solutions, indicating their capacity to grow in these conditions. Moreover, a consortium of isolated bacteria was immobilized in two different biocomposites and the biocomposite with larger pore size achieved greater bacterial immobilization showcasing the potential of these bacteria in biotechnological applications.

The Hypersaline Soils of the Odiel Saltmarshes Natural Area as a Source for Uncovering a New Taxon: Pseudidiomarina terrestris sp. nov.

The hypersaline soils of the Odiel Saltmarshes Natural Area are an extreme environment with high levels of some heavy metals; however, it is a relevant source of prokaryotic diversity that we aim to explore. In this study, six strains related to the halophilic genus Pseudidiomarina were isolated from this habitat. The phylogenetic study based on the 16S rRNA gene sequence and the fingerprinting analysis suggested that they constituted a single new species within the genus Pseudidiomarina. Comparative genomic analysis based on the OGRIs indices and the phylogeny inferred from the core genome were performed considering all the members of the family Idiomarinaceae. Additionally, a completed phenotypic characterization, as well as the fatty acid profile, were also carried out. Due to the characteristics of the habitat, genomic functions related to salinity and high heavy metal concentrations were studied, along with the global metabolism of the six isolates. Last, the ecological distribution of the isolates was studied in different hypersaline environments by genome recruitment. To sum up, the six strains constitute a new species within the genus Pseudidiomarina, for which the name Pseudidiomarina terrestris sp. nov. is proposed. The low abundance in all the studied hypersaline habitats indicates that it belongs to the rare biosphere in these habitats. In silico genome functional analysis suggests the presence of heavy metal transporters and pathways for nitrate reduction and nitrogen assimilation in low availability, among other metabolic traits.

Oil Palm Biomass Sap-Rotten Rice as a Source to Remove Metal Ions and Generate Electricity as By-Products through Microbial Fuel Cell Technology

Microbial fuel cell (MFC) is a new and interesting technology that can be used to treat wastewater without using electricity. The current research focuses on electron generation, which is one of the technique’s major challenges. According to the latest literature, the study was planned to successfully remove the metals from artificial wastewater at high concentrations and generate electricity. On average, after 18 days of operation, it offered 610 mV with 1000 ῼ constant external resistance. The internal resistance was found to be 520 ῼ. The achieved power density was 3.164 mW/m2 at an external resistance of 1000 ῼ. The achieved removal efficiencies of Pb2+, Cd2+, Cr3+, and Ni2+ were 83.67%, 84.10%, 84.55%, and 95.99%, respectively. The operation lasted for 25 days. The cyclic voltameter studies show that there is a gradual oxidation rate of organic substances, while on day 25, the removal efficiency reached its maximum. The specific capacitance was found to be high between days 15 and 20, i.e., 0.0000540 F/g. It also indicated that biofilm was stable around day 18. Furthermore, the biological characterization also demonstrated that MFC operation was very smooth throughout the process, even at high concentrations (100 mg/L) of metal ions. Finally, there is the MFC method, as well as some new challenges and future recommendations.

Improving the efficiency of DNA extraction from iron incrustations and oilfield-produced water

The quantity and quality of DNA isolated from environmental samples are crucial for getting robust high-throughput sequencing data commonly used for microbial community analysis. The differences in the nature and physicochemical properties of environmental samples impact DNA yields, and therefore, an optimisation of the protocols is always recommended. For instance, samples collected from corroded areas contain high concentrations of metals, salts, and hydrocarbons that can interfere with several steps of the DNA extraction protocols, thereby reducing yield and quality. In this study, we compared the efficiency of commercially available DNA extraction kits and laboratory-adopted methods for microbial community analysis of iron incrustations and oilfield-produced water samples. Modifications to the kits manufacturers’ protocols were included to maximise the yield and quality. For iron incrustations, the modified protocol for FastDNA Spin Kit for Soil yielded higher DNA and resulted in higher diversity, including the recovery of low-abundant and rare taxa in the samples, compared to DNeasy PowerSoil Pro Kit. The DNA extracted with modified phenol–chloroform methods yielded higher DNA but failed to pass quality control PCR for 16S sequencing with and without purification. The protocols mentioned here can be used to maximise DNA recovery from iron incrustations and oilfield-produced water samples.

The effect of heavy metals mobility on their bioavailability in Güllük Lagoon, Aegean Sea

The mobility and bioavailability of heavy metals (HMs) were investigated in the Güllük Lagoon, the southern part of the Aegean Sea. Total concentrations and chemical fraction concentrations of Cd, Pb, Cu, Fe, Mn, Zn and Hg in surface sediment, total concentrations of these metals in Mugil cephalus tissues (liver, gill, skin and muscle) and aquatic plant Ludwigia stolonifera were determined using atomic absorption spectrometry (AAS). The Risk Assessment Code used to evaluate the mobility and bioavailability of metals was found to be the highest for Cd, and the Geoaccumulation Index, which indicates the pollution level in the sediment, was found to be the highest for Hg. It was determined that Hg concentrations in the muscle tissue of M. cephalus were higher than the threshold values. Furthermore, the values of the chemical fraction stages and risk assessment code indicated that Cd and Hg were mobile in surface sediment and biota. Based on the results of the study, it can be argued that the anthropogenic activities in the region affect the concentrations of especially Cd, Cu, and Hg in sediment and biota. The high metal concentrations measured in the study show that the study area is under the effect of thermal power plants, domestic, industrial, and agricultural wastes brought by the Sarıçay River, and aquaculture, which is intense in the region. As a result, it is emphasized that potential sources of Hg, Cd, and Cu pollution should be determined and precautions should be taken to protect the ecosystem and public health in Güllük Lagoon in this study.

Bioaccumulation of Metals in Some Auchenorrhyncha (Insecta: Hemiptera) Species in Cherry Orchards Near Motorway and Their Usage as Biomonitor for Metal Pollution.

Traffic borne pollutants negatively affect organisms. This study aimed to determine the impact of traffic pollution on Auchenorrhyncha species and their usage as biomonitor for metal pollution. The study was carried out in the cherry orchard near the Amasya-Samsun D100/E80 motorway in Amasya, Türkiye. Metal concentrations in specimens tended to decrease with the increasing distance from the motorway. Significant variations were determined in some metal concentrations based on distance from the motorway. The maximum and minimum metal concentrations were obtained from 0 to 100m, respectively. Negative relationships were determined between distance from the motorway and Cd, Co, Cr, Cu, Fe, Mn, Ni and Pb concentrations in Arboridia versuta (Melichar, 1897), and Cd, Co, Cr, Cu, Ni and Pb concentrations in Psammotettix provincialis (Ribaut, 1925). Metals were accumulated in the body of specimens. Therefore, it is thought that Auchenorrhyncha species may be used as a biomonitor for metal pollution due to their high metal concentrations.

Applying machine learning random forest (RF) method in predicting the cement products with a co-processing of input materials: Optimizing the hyperparameters

Co-processing recycled waste during cement production, i.e., using alternative materials such as secondary raw materials or secondary raw fuels, is widely practiced in developed countries. Alternative raw materials or fuels contain high concentrations of heavy metals and other hazardous chemicals, which might lead to the potential for dangerous heavy metals and hazardous chemicals to be transferred to clinker or cement products, resulting in exposure and emissions to people or the environment. Managing input materials and predicting which inputs affect the final concentration is essential to prevent potential hazards. We used the data of six heavy metals by input raw materials and input fuels of cement manufacturers in 2016–2017. The concentrations of Pb and Cu in cement were about 10–200 times and 4 to 200 times higher than other heavy metals (Cr, As, Cd, Hg), respectively.We profiled the influence of heavy metal concentration of each input material using the principal component analysis (PCA), which analyzed the leading causes of each heavy metal. The Random Forest (RF) ensemble model predicted cement heavy metal concentrations according to input materials. In the case of Cu, Cd, and Cr, the training performance showed R square values of 0.71, 0.71, and 0.92, respectively, as a result of predicting the cement heavy metal concentration according to the heavy metal concentration of each cement input material using the RF model, which is a machine learning model. The results of this study show that the RF model can be used to predict the amount and concentration of alternative raw materials and alternative fuels by controlling the concentration of heavy metals in cement through the concentration of heavy metals in the input materials.

Genetic variability of New Caledonian Boeckella De Guerne & Richard, 1889 (Copepoda: Calanoida), with the description of a new species

Abstract Thirteen new freshwater populations of the copepod genus BoeckellaDe Guerne & Richard, 1889 were found during three expeditions to New Caledonia (‘La Planète Revisitée,’ 2016-2018). The 12 populations from the Plaine des Lacs, which show remarkable genetic diversity among themselves, were identified as B. spinogibbaDefaye, 1998, the only species of its genus known from New Caledonia until now. The sole exception, the population from Mont-Dore 22 km further east, appeared genetically and morphologically distinct from the others and is described herein as a new species. The two species are distinguished from each other by the shapes of the male and female P5, female Th5, and body colour. A previously published key is amended to separate the species. Our concatenated COI+28S phylogeny places the two New Caledonia species as a new branch within Boeckella, distinct from the branches consisting of South American, Antarctic and Australasian species. All 13 Boeckella populations inhabit the extreme south of New Caledonia, an area known for endemism and high heavy metal concentrations in the soil. Extensive mining activity in this metal-rich area, begun in 1873, is now leading to conflict with conservation goals. By using aerial photographs to trace the fate of the pond that is the type locality of B. spinogibba, we confirmed that it disappeared between 2007 and 2014 as a result of the expansion of the Goro nickel mine.

Fluid chemistry alters faunal trophodynamics but not composition on the deep-sea Capelinhos hydrothermal edifice (Lucky Strike vent field, Mid-Atlantic Ridge)

The recently discovered deep-sea Capelinhos hydrothermal edifice, ~ 1.5 km of the main Lucky Strike (LS) vent field (northern Mid-Atlantic Ridge), contrasts with the other LS edifices in having poorly-altered end-member hydrothermal fluids with low pH and chlorine, and high metal concentrations. Capelinhos unique chemistry and location offer the opportunity to test the effects of local abiotic filters on faunal community structure while avoiding the often-correlated influence of dispersal limitation and depth. In this paper, we characterize for the first time the distribution patterns of the Capelinhos faunal communities, and analyze the benthic invertebrates (> 250 µm) inhabiting diffusive-flow areas and their trophic structures (δ13C, δ15N and δ34S). We hypothesized that faunal communities would differ from those of the nearest LS vent edifices, showing an impoverished species subset due to the potential toxicity of the chemical environment. Conversely, our results show that: (1) community distribution resembles that of other LS edifices, with assemblages visually dominated by shrimps (close to high-temperature focused-fluid areas) and mussels (at low-temperature diffuse flow areas); (2) most species from diffuse flow areas are well-known LS inhabitants, including the bed-forming and chemosymbiotic mussel Bathymodiolus azoricus and (3) communities are as diverse as those of the most diverse LS edifices. On the contrary, stable isotopes suggest different trophodynamics at Capelinhos. The high δ15N and, especially, δ13C and δ34S values suggest an important role of methane oxidation (i.e., methanotrophy), rather than the sulfide oxidation (i.e., thiotrophy) that predominates at most LS edifices. Our results indicate that Capelinhos shows unique environmental conditions, trophic structure and trophodynamics, yet similar fauna, compared to other LS edifices, which suggest a great environmental and trophic plasticity of the vent faunal communities at the LS.

Tepidibacter aestuarii sp. nov., isolated from the Bach Dang Estuary, Haiphong, Vietnam.

A mesophilic, anaerobic, endospore-forming, fermentative bacterium designated strain 8C15bT was isolated from bank sediment of the Bach Dang Estuary, Haiphong, Vietnam. The Bach Dang Estuary, where Haiphong harbour is located, is subject to strong anthropogenic influence, resulting in high concentrations of black carbon and heavy metals. Strain 8C15bT grew optimally at 30 °C, pH 7.5 and with 2.5 % (w/v) NaCl. The main cellular fatty acids consisted of iso-C15 : 0 (51 %), iso-C15:1 ω7c (32 %) and iso-C13 : 0 (5 %). Genomic considerations of strain 8C15bT and comparisons with the phylogenetically closest strains of the genus Tepidibacter provide evidence that Tepidibacter thalassicus SC562T (=DSM 15285T), Tepidibacter formicigenes DV1184T (=DSM 15518T), Tepidibacter mesophilus B1T (=JCM 16806T) and strain 8C15bT could be differentiated at the species level. We propose the name Tepidibacter aestuarii sp. nov. for the type strain 8C15bT (=JCM 35983T=KCTC 25692T). Finally, the nickel-tolerance properties of strain 8C15bT are highlighted in this study.

Contaminated Water Effects on Human Health: A Case of Pakistan

It is vital to have clean water for a healthy lifestyle. Drinking polluted and dirty water causes millions of people to perish. This study's goal was to investigate the effects of tainted water on Rahim Yar Khan's population's health. Rahim Yar Khan's water management and monitoring are subpar, and the city's subsurface water is unfit for drinking because high concentrations of calcium, magnesium, chloride, hardness, and heavy metal are present. The data's empirical component was gathered from hundred replyers in Rahim Yar Khan. The interview schedule was the tool utilized in this study's with the help of purposive sampling for data collection. Descriptive and inferential statistical methods were applied to the data analysis. This study examined public perceptions of the negative health effects after consuming contaminated water and the results shows that high level of diseases are increasing in that selected area just because of drinking contaminated water, some people seemed concerned because of poor hygiene measures for drinking water. The results of this study shows high level of health risk in that selected area for human health.

Modulatory Role of Biochar Properties and Environmental Risk of Heavy Metals by Co-Pyrolysis of Fenton Sludge and Biochemical Sludge.

Recent studies have reported that Fenton sludge and biochemical sludge contain high concentrations of toxic substances and heavy metals (HMs), whereas improper treatment can pose serious threats to environmental safety. Pyrolysis is considered an efficient technology to replace conventional sludge treatment. This study investigated the pyrolysis and kinetic processes of Fenton sludge and biochemical sludge, revealed the physicochemical properties of sludge biochar, and highlighted the role of co-pyrolysis in sludge immobilization of HMs and environmental risks. Results showed that Fenton sludge and biochemical sludge underwent three stages of weight loss during individual pyrolysis and co-pyrolysis, especially co-pyrolysis, which increased the rate of sludge pyrolysis and reduced the decomposition temperature. The kinetic reaction indicated that the activation energies of Fenton sludge, biochemical sludge, and mixed sludge were 11.59 kJ/mol, 8.50 kJ/mol, and 7.11 kJ/mol, respectively. Notably, co-pyrolysis reduced the activation energy of reactions and changed the specific surface area and functional group properties of the biochar produced from sludge. Meanwhile, co-pyrolysis effectively immobilized Cu, Pb, and Zn, increased the proportion of metals in oxidizable and residual states, and mitigated the environmental risks of HMs in sludge. This study provided new insights into the co-pyrolysis properties of sludge biochar and the risk assessment of HMs.

Dynamic adaptation of the extremophilic red microalga Cyanidioschyzon merolae to high nickel stress

The order of Cyanidiales comprises seven acido-thermophilic red microalgal species thriving in hot springs of volcanic origin characterized by extremely low pH, moderately high temperatures and the presence of high concentrations of sulphites and heavy metals that are prohibitive for most other organisms. Little is known about the physiological processes underlying the long-term adaptation of these extremophiles to such hostile environments. Here, we investigated the long-term adaptive responses of a red microalga Cyanidioschyzon merolae, a representative of Cyanidiales, to extremely high nickel concentrations. By the comprehensive physiological, microscopic and elemental analyses we dissected the key physiological processes underlying the long-term adaptation of this model extremophile to high Ni exposure. These include: (i) prevention of significant Ni accumulation inside the cells; (ii) activation of the photoprotective response of non-photochemical quenching; (iii) significant changes of the chloroplast ultrastructure associated with the formation of prolamellar bodies and plastoglobuli together with loosening of the thylakoid membranes; (iv) activation of ROS amelioration machinery; and (v) maintaining the efficient respiratory chain functionality. The dynamically regulated processes identified in this study are discussed in the context of the mechanisms driving the remarkable adaptability of C. merolae to extremely high Ni levels exceeding by several orders of magnitude those found in the natural environment of the microalga. The processes identified in this study provide a solid basis for the future investigation of the specific molecular components and pathways involved in the adaptation of Cyanidiales to the extremely high Ni concentrations.

A decade-long journey shed light on chemical composition and field determination of acid mine drainage in Brazil.

Regular monitoring of Acid Mine Drainage (AMD) is essential for understanding its extent and impact on water resources. Traditional manual sampling methods have limitations, such as limited representativeness and delayed lab analysis. High-frequency monitoring offers an alternative, enabling real-time analysis of AMD fluctuations and determination of constituents in the field. This study assessed a decade-long environmental monitoring database from watersheds impacted by coal mining in Brazil to analyze the relationships between physical properties and constituents from different water sources affected by AMD. Samples were grouped into four categories based on location and contamination levels. Results revealed that water samples from the two groups not affected by AMD exhibited near-neutral pH, low metal and sulfate concentrations, and a large portion of samples below the quantification limit for Mn and Al. In contrast, samples from groups affected by AMD displayed high metal and sulfate concentrations and acidic pH, with the highest contamination observed in the underground mine discharges group (AMD UMD). Spearman correlation analyzes between field (pH and electrical conductivity (EC)) and lab (SO42-, Fe, Mn, and Al) parameters showed no significant correlations in non-AMD-affected groups, but significant correlations in AMD-affected groups, particularly the Streams group. A regression model between sulfate and EC was identified as the best predictor for AMD, enabling continuous, low-cost monitoring of contaminated streams and providing insight into previously unobserved AMD processes, such as variations in contamination during storm events and river flushing.

Draft genome analysis for Enterobacter kobei, a promising lead bioremediation bacterium.

Lead pollution of the environment poses a major global threat to the ecosystem. Bacterial bioremediation offers a promising alternative to traditional methods for removing these pollutants, that are often hindered by various limitations. Our research focused on isolating lead-resistant bacteria from industrial wastewater generated by heavily lead-containing industries. Eight lead-resistant strains were successfully isolated, and subsequently identified through molecular analysis. Among these, Enterobacter kobei FACU6 emerged as a particularly promising candidate, demonstrating an efficient lead removal rate of 83.4% and a remarkable lead absorption capacity of 571.9mg/g dry weight. Furthermore, E. kobei FACU6 displayed a remarkable a maximum tolerance concentration (MTC) for lead reaching 3,000mg/L. To further investigate the morphological changes in E. kobei FACU6 in response to lead exposure, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed. These analyses revealed significant lead adsorption and intracellular accumulation in treated bacteria in contrast to the control bacterium. Whole-genome sequencing was performed to gain deeper insights into E. kobei's lead resistance mechanisms. Structural annotation revealed a genome size of 4,856,454bp, with a G + C content of 55.06%. The genome encodes 4,655 coding sequences (CDS), 75 tRNA genes, and 4 rRNA genes. Notably, genes associated with heavy metal resistance and their corresponding regulatory elements were identified within the genome. Furthermore, the expression levels of four specific heavy metal resistance genes were evaluated. Our findings revealed a statistically significant upregulation in gene expression under specific environmental conditions, including pH 7, temperature of 30°C, and high concentrations of heavy metals. The outstanding potential of E. kobei FACU6 as a source of diverse genes related to heavy metal resistance and plant growth promotion makes it a valuable candidate for developing safe and effective strategies for heavy metal disposal.

Fitness factors impacting survival of a subsurface bacterium in contaminated groundwater.

Many factors contribute to the ability of a microbial species to persist when encountering complexly contaminated environments, including time of exposure, the nature and concentration of contaminants, availability of nutritional resources, and possession of a combination of appropriate molecular mechanisms needed for survival. Herein we sought to identify genes that are most important for survival of Gram-negative Enterobacteriaceae in contaminated groundwater environments containing high concentrations of nitrate and metals using the metal-tolerant Oak Ridge Reservation isolate, Pantoea sp. MT58 (MT58). Survival fitness experiments in which a randomly barcoded transposon insertion (RB-TnSeq) library of MT58 was exposed directly to contaminated Oak Ridge Reservation groundwater samples from across a nitrate and mixed metal contamination plume were used to identify genes important for survival with increasing exposure times and concentrations of contaminants, and availability of a carbon source. Genes involved in controlling and using carbon, encoding transcriptional regulators, and related to Gram-negative outer membrane processes were among those found to be important for survival in contaminated Oak Ridge Reservation groundwater. A comparative genomics analysis of 75 Pantoea genus strains allowed us to further separate the survival determinants into core and non-core genes in the Pantoea pangenome, revealing insights into the survival of subsurface microorganisms during contaminant plume intrusion.

Egg Quality and Heavy Metal Concentrations in Meat, Eggs and Inner Organs of Laying Ducks Fed under a Conventional Feeding in Lombok, Indonesia

The search for alternative protein sources for duck feed is important considering its high cost. An experiment involving 100 forty-wk-old laying ducks was conducted for eight weeks to study the effects of fresh water fish (sapu-sapu fish -SSF) as single protein sources on egg quality and heavy metal concentration. The SSF levels were 28 and 35% of the feed and the remaining constituent was rice bran with metabolizable energy approximately 2,943 and 2,934 kcal/kg, respectively. Fresh water fish did not effect on egg quality measured except egg weight and shell thickness (63.2±0.30 to 67.9±0.22g) and shell thickness (0.50±0.04 to 0.52±0.04g) with increasing dietary SFF(P<0.05). Mean concentrations of heavy metals in local duck samples decreased in the order kidney>liver>egg>meat for Pb and liver>kidney>meat>egg for Cu. Lead concentrations in meat, eggs, liver and kidney were 1.267± 0.825, 1.311±0.737, 1.762±0.729 and 2.172±0.770 mg/kg respectively. These values were higher than the admissible amounts under the Indonesian National Standards (1.0 mg Pb/kg) and FAO (0.1 mg Pb/kg). Accumulation of Cu in the meat, eggs, liver and kidney was 12.798±4.181, 7.011±1.949, 30.165±16.561 and 14.392± 4.208 mg/kg respectively. These levels were also higher than that recommended by the European Commission. The conclusion of this study proved that feeding SSF to laying ducks raised by small farmers contained a significantly high concentration of heavy metals not appropriate for human consumption when high levels of SSF was fed

Exploring adsorption capacity and mechanisms involved in cadmium removal from aqueous solutions by biochar derived from euhalophyte

Biochar has shown potential as a sorbent for reducing Cd levels in water. Euhalophytes, which thrive in saline-alkali soils containing high concentrations of metal ions and anions, present an intriguing opportunity for producing biochar with inherent metal adsorption properties. This study focused on biochar derived from the euhalophyte Salicornia europaea and aimed to investigate its Cd adsorption capacity through adsorption kinetics and isotherm experiments. The results demonstrated that S. europaea biochar exhibited a high specific surface area, substantial base cation content, and a low negative surface charge, making it a highly effective adsorbent for Cd. The adsorption data fit well with the Langmuir isotherm model, revealing a maximum adsorption capacity of 108.54 mg g−1 at 25 °C. The adsorption process involved both surface adsorption and intraparticle diffusion. The Cd adsorption mechanism on the biochar encompassed precipitation, ion exchange, functional group complexation, and cation-π interactions. Notably, the precipitation of Cd2+ with CO32− in the biochar played a dominant role, accounting for 73.7% of the overall removal mechanism. These findings underscore the potential of euhalophytes such as S. europaea as a promising solution for remediating Cd contamination in aquatic environments.

Euglena mutabilis exists in a FAB consortium with microbes that enhance cadmium tolerance

BackgroundSynthetic algal–fungal and algal–bacterial cultures have been investigated as a means to enhance the technological applications of the algae. This inclusion of other microbes has enhanced growth and improved stress tolerance of the algal culture. The goal of the current study was to investigate natural microbial consortia to gain an understanding of the occurrence and benefits of these associations in nature. The photosynthetic protist Euglena mutabilis is often found in association with other microbes in acidic environments with high heavy metal (HM) concentrations. This may suggest that microbial interactions are essential for the protist’s ability to tolerate these extreme environments. Our study assessed the Cd tolerance of a natural fungal–algal–bacterial (FAB) association whereby the algae is E. mutabilis.ResultsThis study provides the first assessment of antibiotic and antimycotic agents on an E. mutabilis culture. The results indicate that antibiotic and antimycotic applications significantly decreased the viability of E. mutabilis cells when they were also exposed to Cd. Similar antibiotic treatments of E. gracilis cultures had variable or non-significant impacts on Cd tolerance. E. gracilis also recovered better after pre-treatment with antibiotics and Cd than did E. mutabilis. The recoveries were assessed by heterotrophic growth without antibiotics or Cd. In contrast, both Euglena species displayed increased chlorophyll production upon Cd exposure. PacBio full-length amplicon sequencing and targeted Sanger sequencing identified the microbial species present in the E. mutabilis culture to be the fungus Talaromyces sp. and the bacterium Acidiphilium acidophilum.ConclusionThis study uncovers a possible fungal, algal, and bacterial relationship, what we refer to as a FAB consortium. The members of this consortium interact to enhance the response to Cd exposure. This results in a E. mutabilis culture that has a higher tolerance to Cd than the axenic E. gracilis. The description of this interaction provides a basis for explore the benefits of natural interactions. This will provide knowledge and direction for use when creating or maintaining FAB interactions for biotechnological purposes, including bioremediation.

A high-quality chromosomal genome assembly of the sea cucumber Chiridota heheva and its hydrothermal adaptation.

Chiridota heheva is a cosmopolitan holothurian well adapted to diverse deep-sea ecosystems, especially chemosynthetic environments. Besides high hydrostatic pressure and limited light, high concentrations of metal ions also represent harsh conditions in hydrothermal environments. Few holothurian species can live in such extreme conditions. Therefore, it is valuable to elucidate the adaptive genetic mechanisms of C. heheva in hydrothermal environments. Herein, we report a high-quality reference genome assembly of C. heheva from the Kairei vent, which is the first chromosome-level genome of Apodida. The chromosome-level genome size was 1.43 Gb, with a scaffold N50 of 53.24 Mb and BUSCO completeness score of 94.5%. Contig sequences were clustered, ordered, and assembled into 19 natural chromosomes. Comparative genome analysis found that the expanded gene families and positively selected genes of C. heheva were involved in the DNA damage repair process. The expanded gene families and the unique genes contributed to maintaining iron homeostasis in an iron-enriched environment. The positively selected gene RFC2 with 10 positively selected sites played an essential role in DNA repair under extreme environments. This first chromosome-level genome assembly of C. heheva reveals the hydrothermal adaptation of holothurians. As the first chromosome-level genome of order Apodida, this genome will provide the resource for investigating the evolution of class Holothuroidea.