Heavy Metal Resistance Research Articles

Exploring Viral Interactions in Clavibacter Species: In Silico Analysis of Prophage Prevalence and Antiviral Defenses

Clavibacter is a phytopathogenic genus that causes severe diseases in economically important crops, yet the role of prophages in its evolution, pathogenicity, and adaptation remains poorly understood. In this study, we used PHASTER, Prophage Hunter, and VirSorter2 to identify prophage-like sequences in publicly available Clavibacter genomes. Prophage predictions were checked by hand to make them more accurate. We identified 353 prophages, predominantly in chromosomes, with some detected phage-plasmids. Most prophages exhibited traits of advanced domestication, such as an unimodal genome length distribution, reduced numbers of integrases, and minimal transposable elements, suggesting long-term interactions with their bacterial hosts. Comparative genomic analyses uncovered high genetic diversity, with distinct prophage clusters showing species-specific and interspecies conservation patterns. Functional annotation revealed prophage-encoded genes were involved in sugar metabolism, heavy metal resistance, virulence factors, and antibiotic resistance, highlighting their contribution to host fitness and environmental adaptation. Defense system analyses revealed that, despite lacking CRISPR-Cas, Clavibacter genomes harbor diverse antiviral systems, including PD-Lambda-1, AbiE, and MMB_gp29_gp30, some encoded within prophages. These findings underscore the pervasive presence of prophages in Clavibacter and their role in shaping bacterial adaptability and evolution.

Unraveling nitrogen metabolism, cold and stress adaptation in polar Bosea sp. PAMC26642 through comparative genome analysis

Nitrogen metabolism, related genes, and other stress-resistance genes are poorly understood in Bosea strain. To date, most of the research work in Bosea strains has been focused on thiosulfate oxidation and arsenic reduction. This work aimed to better understand and identify genomic features that enable thiosulfate-oxidizing lichen-associated Bosea sp. PAMC26642 from the Arctic region of Svalbard, Norway, to withstand harsh environments. Comparative genomic analysis was performed using various bioinformatics tools to compare Bosea sp. PAMC26642 with other strains of the same genus, emphasizing nitrogen metabolism and stress adaptability. During genomic analysis of Bosea sp. PAMC26642, assimilatory nitrogen metabolic pathway and its associated enzymes such as nitrate reductase, NAD(P)H-nitrite reductase, ferredoxin-nitrite reductase, glutamine synthetase, glutamine synthase, and glutamate dehydrogenase were identified. In addition, carbonic anhydrase, cyanate lyase, and nitronate monooxygenase were also identified. Furthermore, the strain demonstrated nitrate reduction at two different temperatures (15°C and 25°C). Enzymes associated with various stress adaptation pathways, including oxidative stress (superoxide dismutase, catalase, and thiol peroxidase), osmotic stress (OmpR), temperature stress (Csp and Hsp), and heavy metal resistance, were also identified. The average Nucleotide Identity (ANI) value is found to be below the threshold of 94-95%, indicating this bacterium might be a potential new species. This study is very helpful in determining the diversity of thiosulfate-oxidizing nitrate-reducing bacteria, as well as their ability to adapt to extreme environments. These bacteria can be used in the future for environmental, biotechnological, and agricultural purposes, particularly in processes involving sulfur and nitrogen transformation.

Ecogenomic insights into the resilience of keystone Blastococcus Species in extreme environments: a comprehensive analysis

BackgroundThe stone-dwelling genus Blastococcus plays a key role in ecosystems facing extreme conditions such as drought, salinity, alkalinity, and heavy metal contamination. Despite its ecological significance, little is known about the genomic factors underpinning its adaptability and resilience in such harsh environments. This study investigates the genomic basis of Blastococcus's adaptability within its specific microniches, offering insights into its potential for biotechnological applications.ResultsComprehensive pangenome analysis revealed that Blastococcus possesses a highly dynamic genetic composition, characterized by a small core genome and a large accessory genome, indicating significant genomic plasticity. Ecogenomic assessments highlighted the genus's capabilities in substrate degradation, nutrient transport, and stress tolerance, particularly on stone surfaces and archaeological sites. The strains also exhibited plant growth-promoting traits, enhanced heavy metal resistance, and the ability to degrade environmental pollutants, positioning Blastococcus as a candidate for sustainable agriculture and bioremediation. Interestingly, no correlation was found between the ecological or plant growth-promoting traits (PGPR) of the strains and their isolation source, suggesting that these traits are not linked to their specific environments.ConclusionsThis research highlights the ecological and biotechnological potential of Blastococcus species in ecosystem health, soil fertility improvement, and stress mitigation strategies. It calls for further studies on the adaptation mechanisms of the genus, emphasizing the need to validate these findings through wet lab experiments. This study enhances our understanding of microbial ecology in extreme environments and supports the use of Blastococcus in environmental management, particularly in soil remediation and sustainable agricultural practices.

Investigation of multiple resistance frequencies (antibiotic and heavy metal) of bacteria isolated from Gökçeada Island coastal marine sediment

Marine sediments are important reservoirs for antibiotics and heavy metals. Bacteria play a key role in polluted sedimentary habitats. This study aimed to identify heavy metal and antibiotic resistance in marine sediment bacteria isolated from Gökçeada Island in Turkiye. The samples were collected seasonally from 10 different sampling stations in 2015. Ninety isolates determined by VITEK 2 were tested against seven antibiotics using the disk diffusion method. The minimum inhibitory concentration values were measured against four heavy metal salts. The antibiotic resistance frequency rates were ordered as sulphonamides compound (93.3%), cefotaxime (78.9), ampicillin (77.8%), oxacillin (67.8%), rifampicin (57.8%), imipenem (1.1%), and oxytetracycline (0%). The heavy metal resistance ratios against ZnCl2, CuSO4, Pb(CH3COO)2, and HgCl2 were measured as 100%, 100%, 96.7%, and 73.3% respectively. The multiple heavy metal resistance index values were ranged from 0.75 (22.2%) to 1.0 (77.8%). The results show significant heavy metal and antibiotic contamination in the sediments of the Gökçeada Island. It is recommended that measures be taken against antibiotics and heavy metal pollution, as well as identifying and monitoring critical control points.

A novel immobilized bacteria consortium enhanced remediation efficiency of PAHs in soil: Insights into key removal mechanism and main driving factor.

The remediation of sites co-contaminated with polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs) poses challenges for efficient and ecofriendly restoration methods. In this study, three strains (Pseudomonas sp. PDC-1, Rhodococcus sp. RDC-1, and Enterobacter sp. EDC-1) were isolated from sites contaminated with PAHs and HMs. The constructed bacteria consortium was then immobilized using biochar, bentonite, and peat. The immobilized bacteria consortium (IBC) demonstrated efficient removal ability of phenanthrene (58.1 %-73.4 %) and benzo[a]pyrene (69.6 %-83.5 %) during 60 days. Additionally, the IBC decreased soil bacterial richness and diversity, but increased the relative abundance of Proteobacteria phylum and Ochrobactrum genus, which were capable of degrading PAHs. Soil microbial co-occurrence network with IBC was classified into three main modules, and 14 genera were identified as keystone taxa linked to PAHs degradation and HMs resistance. The IBC enhanced the dioxygenase metabolic pathways for PAHs degradation, including phthalic acid and salicylic acid pathways, which became the main driving factor affecting PAHs removal efficiency based on the structural equation modeling analysis. This study confirmed the potential application of the constructed IBC in the bioremediation of soil co-contaminated with PAHs-HMs, and provides insights into key removal mechanism and main driving factor of the enhanced elimination of PAHs.

Draft genome sequence of Modicisalibacter sp. strain Wilcox isolated from produced water.

The draft genome sequence of Modicisalibacter sp. strain Wilcox, isolated from produced water, is presented. The genome is 3.6 Mb in size with 3,283 protein-coding genes, including genes for hydrocarbon degradation, heavy metal resistance, and adaptation to high salinity. This genome provides insights into molecular mechanisms of hydrocarbon degradation under hypersaline conditions.

Heavy metals-resistant PGPR strains of <i>Pseudomonas </i> sp. stimulating the growth of alfalfa under cadmium stress

Three bacteria strains of Pseudomonas sp. resistant to heavy metals were isolated from the chemically contaminated soil. According to the results on the nucleotide sequences of the 16S rRNA and rpoD genes, strain Pseudomonas sp. 17 НМ was identified as Pseudomonas capeferrum, and the strains of Pseudomonas sp. 65 НМ и 67 НМ were most closely related to the type strain of Pseudomonas silesiensis и Pseudomonas umsongensis, respectively. It has been shown that strains of Pseudomonas sp. 17 НМ, 65 НМ, 67 НМ are characterized by different levels of resistance of heavy metals: maximum tolerance concentration (MTC) of zinc was 1 mМ for all strains, cadmium 1, 1.5, 1 mМ, lead 5, 5, 4 mМ, nickel 7, 9, 7 mМ, respectively. All pseudomonad strains can form biofilms and have the properties of PGPR bacteria. Treatment of alfalfa seeds (Medicago sativa L.) with strains Pseudomonas sp. 17 НМ, 65 НМ, 67 НМ under cadmium stress led to an increase in the dry weight of alfalfa seedling up to 40 % and the content of chlorophyll a and b in the leaves by 25-33% relative to the control.

Digital insights into Pseudomonas aeruginosa PBH03: in-silico analysis for genomic toolbox and unraveling cues for heavy metal bioremediation.

The genomes of publicly available electroactive Pseudomonas aeruginosa strains are currently limited to in-silico analyses. This study analyzed the electroactive Pseudomonas aeruginosa PBH03 genome using comparative in-silico studies for biotechnological applications. Comparative in-silico and experimental analyses were conducted to identify the novel traits of P. aeruginosa PBH03 by genome sequencing. The publicly available genomes of Pseudomonas aeruginosa strains (PA01, PA14, and KRP1) were used for a comparative in-silico study with PBH03. Genome assembly, annotation, phylogenetic analysis, metabolic reconstruction, and comparative functional genes analysis were conducted using bioinformatics tools. The experimental analyses were conducted to validate the heavy metal resistance (Hg and Cu), salinity tolerance levels of PBH03, and acetate assimilation under microaerobic conditions. Computational analysis showed that the PBH03 genome had a size of 6.8Mb base pairs with a GC content of 65.7%. Whole genome annotation identified the unique genes absent in the previously sequenced Pseudomonas aeruginosa genomes. These genes were associated with resistance to heavy metals, such as Cu, Hg, As, and a Co-Zn-Cd efflux system. In addition, clustered, regularly interspaced short palindromic repeats, transposable elements, and conjugative transfer proteins were observed in the clustering-based systems. The strain exhibited resistance to Hg (150mg/L) and Cu (500mg/L) and showed growth at salinity levels of 40g/L (typical sea/ocean levels). PBH03 could consume acetate up to 110mM. Integrating in-silico and experimental data highlights the intriguing adaptive genomic qualities of PBH03, making it a promising candidate for various biotechnological applications.

Cadmium-Induced Oxidative Damage and the Expression and Function of Mitochondrial Thioredoxin in Phascolosoma esculenta.

Phascolosoma esculenta is a unique aquatic invertebrate native to China, whose habitat is highly susceptible to environmental pollution, making it an ideal model for studying aquatic toxicology. Mitochondrial thioredoxin (Trx2), a key component of the Trx system, plays an essential role in scavenging reactive oxygen species (ROS), regulating mitochondrial membrane potential, and preventing ROS-induced oxidative stress and apoptosis. This study investigated the toxicity of cadmium (Cd) on P. esculenta and the role of P. esculenta Trx2 (PeTrx2) in Cd detoxification. The results showed that Cd stress altered the activities of T-SOD and CAT, as well as the contents of GSH and MDA in the intestine. After 96 h of exposure, histological damages such as vacuolization, cell necrosis, and mitophagy were observed. Suggesting that Cd stress caused oxidative damage in P. esculenta. Furthermore, with the prolongation of stress time, the expression level of intestinal PeTrx2 mRNA initially increased and then decreased. The recombinant PeTrx2 (rPeTrx2) protein displayed dose-dependent redox activity and antioxidant capacity and enhanced Cd tolerance of Escherichia coli. After RNA interference (RNAi) with PeTrx2, significant changes in the expression of apoptosis-related genes (Caspase-3, Bax, Bcl-2, and Bcl-XL) were observed. Proving that PeTrx2 rapidly responded to Cd stress and played a vital role in mitigating Cd-induced oxidative stress and apoptosis. Our study demonstrated that PeTrx2 is a key factor for P. esculenta to endure the toxicity of Cd, providing foundational data for further exploration of the molecular mechanisms underlying heavy metal resistance in P. esculenta.

Uncovering the Relationship Between Soil Bacterial Community and Heavy Metals in a Copper Waste Pile

In the present study, the relationship between the microbial community and heavy metal content of soil was analyzed based on 16S rRNA gene high-throughput sequencing, in order to screen the corresponding heavy metal-resistant bacteria in a copper mine waste dump and adjacent shrubbery. Approximately 22 phyla, 57 classes, 128 orders, 173 families, 263 genera, 433 species, and 954 OUTs obtained from soil sample species annotation indicated the Spearman relevance analysis at the phylum level. Specifically, Gemmatimonadota is positively correlated with arsenic (As); Patescibacteria is positively correlated with arsenic (As), copper (Cu), and cadmium (Cd); Proteobacteria is positively correlated with chromium (Cr); and Acidobacteriota is positively correlated with cadmium (Cd), respectively. Meanwhile, at the genus level, Acidibacter is positively correlated with arsenic (As); norank_f__LWQ8, norank_f__Gemmataceae, and Bryobacter are positively correlated with cadmium (Cd); Acidiphilium and Conexiactor are positively correlated with Zinc (Zn); norank_f__norank_o__IMCC26256 is positively correlated with nickel (Ni); norank_f__norank_o__norank_c__AD3 is positively correlated with manganese (Mn), and nickel (Ni); and Alicyclobacillus and unclassified_f__Acidiferobactereae are positively correlated with chromium (Cr). These bacterial flora are significantly and positively related to the resistance of heavy metals, which provides a promising reference for the development of in situ remediation of heavy metal pollution in mines.

A Review on Bioremediation Using Nanobiotechnology and Microbial Heavy Metal Resistance Mechanisms

Abstract: Various human actions have raised the level of heavy metal (HM) pollution in the environment. From contaminated water and soil, the HMs infiltrate into the agricultural crops that are consumed by animals as well humans. Deposition of heavy metals leads to DNA damage and several digestive, reproductive, and respiratory system-related health problems. Various microorganisms have evolved mechanisms of HM resistance, tolerance, detoxification, and metabolization. Physicochemical methods of HM treatment are expensive and non-ecofriendly. Therefore, remediation of contaminated soil and water using microorganisms or bioremediation has become a topic of interest for scientists. Bioremediation is a cheaper, eco-friendly and more efficient method. The present review attempts to describe various mechanisms (biosorption, bioaccumulation, biotransformation and active export) by which microbes resist and remediate heavy metal pollution. In addition, the role of different types of consortia/co-culture in bioremediation has been discussed. Microbes, such as fungi, bacteria, and protozoa can remove metals both singly and in amalgamation. Furthermore, an advanced nanotechnology approach for metal ion treatment from wastewater has been briefly discussed. To fully utilize the microbial potential for heavy metal removal and create better strategies to alleviate environmental pollution, a deeper knowledge of the molecular, biochemical, and genetic mechanisms used by these species is required.

Vertical migration of bacteria bearing antibiotic resistance genes and heavy metal resistance genes through a soil profile as affected by manure

Vertical migration of bacteria bearing antibiotic resistance genes and heavy metal resistance genes through a soil profile as affected by manure

Combining gamma-radiation and bioaugmentation enhances wastewater’s quality for its reuse in agricultural purposes

ABSTRACT The reuse of wastewater in agriculture can be environmentally beneficial due to its abundance of nutrients that promote plant growth and soil fertility. However, wastewater effluents (WWE) are often considered sources of dissemination of bacteria, antibiotics, heavy metal resistance genes, and pathogens. In this study, we employed a combination of gamma irradiation and bioaugmentation as a strategy for WWE treatment. Gamma irradiation facilitates the elimination of pathogens and the degradation of complex organic matter, while bioaugmentation utilises a consortium of microorganisms specialised in metal sorption. Bacterial strains were isolated from soils irrigated with WWE and selected based on their tolerance to Cd (0.2 g L−1), Pb (1 g L−1) and Cu (1.5 g L−1). A consortium composed of Bacillus selenatarsenatis S53, Bacillus thuringiensis S15, and Staphylococcus edaphicus S107 was selected for their metal biosorption capacity, which was evaluated after 24 h of incubation in gamma-irradiated WWE (WWEI). The treated WWE was then used for pea (Pisum sativum L.) seeds germination over a 9 days’ period. The bacterial consortium successfully biosorbed 180, 8085, and 125 µg g−1 dry weight of Cd, Pb, and Cu, respectively, when incubated in WWEI. Seed imbibition with bioaugmented WWEI (WWEIB) resulted in significant increases in radicle and epicotyl elongation compared to germination in WWE (+91.6% and +123.7%, respectively). Additionally, there was an improvement in fresh biomass production for seedlings hydrated with WWEIB compared to WWE. Overall, this strategy appears highly promising for the safe reuse of WWE and enhancing crop productivity by mitigating contaminant-induced plant stress.

Inorganic and organic additives differently regulate compost microbiomes in response to heavy metals immobilization

Various composting additives, both organic and inorganic, have been used to effectively reduce the bioavailability of heavy metals (HMs) in compost. However, a comprehensive assessment of their comparative contributions and the mechanisms involved is still lacking. In this study, we selected shell powder and biochar as representative amendments to assess their efficacy in immobilizing various HMs. Our results demonstrated that the addition of shell powder and biochar markedly enhanced the synthesis of humic acids (HA), reduced the bioavailability of HMs, and indirectly enhanced microbial carbon metabolism and growth pathways. This enhancement subsequently enriched the abundance of key HA synthesis contributors, including Enterobacter, Thermobispora, Pseudomonas, and Sphingobacterium, creating a positive feedback loop. Additionally, adding biochar altered the abundance of Pseudomonas, Chelatococcus, and Pseudoxanthomonas during the mesophilic phase, thereby reducing the expression of HMs resistance genes (HMRGs). In contrast, shell powder supplementation modulated the response to HMRGs reduction by regulating the abundance of Sphingobacterium, Pseudomonas, and Thermobispora during the thermophilic phase. Ultimately, regional cultivation trials confirmed the potential of these innovative organic fertilizers to significantly reduce the spread of HMs to plants. Collectively, these findings highlighted the similarities and differences between organic and inorganic additives to modulate microbial community responses during HMs immobilization, providing a theoretical framework for diminishing the risks associated with HMs dissemination and improving the quality of organic fertilizers.

Effect of heavy metal on growth of black soldier fly larvae (Hermetia illucens): Accumulation, excretion and gut microbiome

AbstractThe larvae of black soldier fly, Hermetia illucens (L.) (Diptera: Stratiomyidae), are an excellent source of feed for animals and have emerged as a promising candidate for waste disposal. The larval growth can be impacted by the intake of heavy metals. However, the underlying mechanism for metal tolerance of the gut microbiome is still poorly understood, as well as how heavy metals, especially in combination, affect the communities of bacteria in the larval gut. Therefore, in this study we focus on how Cu and Zn affect larval growth and gut microbiome, as well as how bioaccumulated heavy metals are distributed in larval residues and bodies. The larval biomass growth was both significantly improved and inhibited by exposure to low and high Cu and Zn concentration, respectively, including in combination. The amount of accumulated Cu and Zn in larval residues and bodies significantly increases as the exposure concentration is increased. In larval bodies, Zn was more likely to be accumulated (57.2%–78.5%) than Cu (<40%). More importantly, the larval gut microbiome was found to be remarkably altered by Cu and Zn exposure, particularly for species of the phyla Actinobacteria, Bacteroidetes, and Firmicutes. In addition, with the exception of the Cu at 400 mg kg−1 exposure, the diversity and complexity of the gut bacterial community significantly decreased. Functional genes related to heavy metal resistance and transport, such as pcoB, pcoD, copC, pccA, ABC.ZM.S, and yahk, were clearly enriched in the larval gut, which may help to partly account for the ability of black soldier fly larvae to tolerate metals.

Prevalence, virulence potential, antibiotic resistance profile, heavy metal resistance genes of Listeria innocua: A first study in consumed foods for assessment of human health risk in Northern Turkey.

Listeria (L.) innocua is typically considered a non-pathogenic bacterium that can sometimes act as an opportunistic pathogen in severely immunocompromised patients. However, it plays an important role in food safety because it acts as an indicator organism for potential contamination and the effectiveness of sanitation methods. The aim of this study was to determine the prevalence, virulence genes, antibiotic resistance profiles, heavy metal and disinfectant resistance genes of L. innocua isolates from animal-derived foods. In this study, we isolated and characterized 39 L. innocua strains recovered from commonly 400 consumed beef meat, fresh fish meat, raw cow milk, and traditional cheese samples collected in Giresun, Turkey. The occurrence of virulence-associated genes was detected, such as plcA (97.4%), iap (35.8%), and hlyA (15.3%). A high incidence of resistance was recorded for fusidic acid (100%), followed by oxacillin (97.4%), clindamycin (82%), trimethoprim/sulfamethoxazole (69.2%), benzylpenicillin (41%), nitrofurantoin (35.8%), and fosfomycin (35.8%). Overall, 100% (39/39) of the isolates were resistant to at least one antibiotic, while 92.3% (36/39) of the isolate strains were multidrug resistant in the antimicrobial susceptibility tested. Among the L. innocua isolates (n = 39), 51.2%, 38.4%, 20.5%, 7.6%, 5.1%, 2.5%, and 2.5% were positive for qacH, cadA1, qacE, qacEΔ1-sul, qacJ, qacF, and qacG heavy metal and disinfectant resistance genes, respectively. The results highlight the need for more comprehensive studies to understand the monitoring and surveillance of L. innocua and their potential hazards to both humans and animals.

Microplastics alter the migration and transformation of vanadium in the riverine sediment environment

Microplastics (MPs, size <5 mm) have emerged as environmental hazards and are widespread in the environment. They can significantly alter the reactivity and mobility of co-occurring elements. Vanadium, a strategic resource, was witnessed rising in the environment because of extensive anthropogenic activities. Nevertheless, the impact of MPs on the migration and transformation of vanadium has yet been investigated. This study therefore investigated the vanadium behavior in riverine sediment and overlying river water in the presence of MPs. 1.5 g representative non-degradable MPs (polyamide, polyethylene terephthalate) and biodegradable MPs (polybutylene succinate, polyhydroxyalkanoates) were separately amended into the reactors, which contained 50 mg vanadium-rich sediment. After incubation for 60 days, vanadium in the sediments decreased substantially, while vanadium increased in the overlying water, especially in reactors amended with biodegradable MPs. The biodegradable and non-degradable MPs were found to influence vanadium behavior through distinct mechanisms. The amendment of non-degradable MPs did not substantially impact humification process, during which the mobile and reducible vanadium passively leached out from the riverine sediment and migrated into overlying water. Conversely, amendment of biodegradable MPs significantly enriched several microbial genera (e.g., Massilia) in the MPs biofilm. These genera confer heavy metal resistance and synthetic polymer degradability, and were significantly correlated with specific sediment organic matter components (C3, Ex/Em = 270/352; C4, Ex/Em = 280(370)/504). The microbial community was found to alter sediment DOM when biodegradable MPs were introduced. These changes in microbial dynamics and sediment chemistry subsequently influenced the bioavailability and mobility of vanadium within the riverine sediment.

Novel Photoelectron-Assisted Microbial Reduction of Arsenate Driven by Photosensitive Dissolved Organic Matter in Mine Stream Sediments.

The microbial reduction of arsenate (As(V)) significantly contributes to arsenic migration in mine stream sediment, primarily driven by heterotrophic microorganisms using dissolved organic matter (DOM) as a carbon source. This study reveals a novel reduction pathway in sediments that photosensitive DOM generates photoelectrons to stimulate diverse nonphototrophic microorganisms to reduce As(V). This microbial photoelectrophic As(V) reduction (PEAsR) was investigated using microcosm incubation, which showed the transfer of photoelectrons from DOM to indigenous sediment microorganisms, thereby leading to a 50% higher microbial reduction rate of As(V). The abundance of two marker genes for As(V) reduction, arrA and arsC, increased substantially, confirming the microbial nature of PEAsR rather than a photoelectrochemical process. Photoelectron ion is unlikely to stimulate photolithoautotrophic growth. Instead, diverse nonphototrophic genera, e.g., Cupriavidus, Sphingopyxis, Mycobacterium, and Bradyrhizobium, spanning 13 orders became enriched by 10-50 folds. Metagenomic binning revealed their genetic potential to mediate the photoelectron-assisted reduction of As(V). These microorganisms contain essential genes involved in respiratory As(V) reduction, detoxification As(V) reduction, dimethyl sulfoxide reductase family, c-type cytochromes, and multiple heavy-metal resistance but lack a complete photosynthesis system. The novel microbial PEAsR pathway offers new insights into the interaction between photoelectron utilization and nonphototrophic As(V)-reducing microorganisms, which may have profound implications for arsenic pollution transportation in mine stream sediment.

Recovery of clinically relevant multidrug-resistant Klebsiella pneumoniae lineages from wastewater in Kumasi Metropolis, Ghana.

Antimicrobial resistance (AMR) is under-monitored in Africa, with few reports characterizing resistant bacteria from the environment. This study examined physicochemical parameters, chemical contaminants and antibiotic-resistant bacteria in waste stabilization pond effluents, hospital wastewater and domestic wastewater from four sewerage sites in Kumasi. The bacteria isolates were sequenced. Three sites exceeded national guidelines for total suspended solids, biochemical oxygen demand, chemical oxygen demand and electrical conductivity. Although sulfamethoxazole levels were low, the antibiotic was detected at all sites. Multi-drug-resistant Klebsiella pneumoniae and Pseudomonas aeruginosa were isolated with multi-locus sequence typing identifying K. pneumoniae strains as ST18 and ST147, and P. aeruginosa as ST235, all of clinical relevance. A comparison of ST147 genomes with isolates from human infections in Africa showed remarkable similarity and shared AMR profiles. Thirteen of the twenty-one plasmids from ST147 harbored at least one AMR gene, including blaCTX-M-15 linked to copper-resistance genes. Our study demonstrated high bacterial counts and organic matter in the analysed wastewater. The recovery of clinically significant isolates with multiple antibiotic and heavy metal resistance genes from the wastewater samples raises public health concerns.

More than a contaminant: How zinc promotes carbonate-mineralizing bacteria metabolism and adaptation by reshaping precipitation conditions

Although microbial-induced carbonate precipitation (MICP) technology is both environmentally friendly and cost-effective, its efficiency is constrained by challenges such as low bacterial activity and heavy metal stress. This study explored the enhancement of mineralization efficiency by incorporating zinc (Zn) into the cultivation system of carbonate-mineralized bacteria. All Zn salts at a concentration of 30 μmol/L significantly enhanced the density and heavy metal resistance of bacterial cells, while also promoting CO2 hydration efficiency. The activities of urease and carbonic anhydrase (CA) were significantly elevated after treatment with 30 μmol/L ZnCl2 and Zn(C3H5O3)2 (ZnL) compared to the control. The results from qRT-PCR and ELISA confirmed that ZnL exhibited a stable biological effect on CA gene expression. Through the analysis of surface chemistry of cells and the subcellular distribution pattern of cadmium (Cd), it was observed that Zn supplementation maintained the cell surface stability and strengthened the cellular barrier against Cd uptake. SEM, FTIR and XRD results further confirmed that Zn supplementation significantly increased the complexity of the mineral morphology, resulting in a more stable crystal structure of CdCO3. This study offers additional theoretical and technical backing, opening a new avenue for the practical application of MICP technology in heavy metal remediation.