Metal-resistant Bacteria Research Articles

Linking the transcriptome to physiology: response of the proteome of cupriavidus metallidurans to changing metal availability.

Cupriavidus metallidurans CH34 is a metal-resistant bacterium. Its metal homeostasis is based on a flow equilibrium of metal ion uptake and efflux reactions, which adapts to changing metal concentrations within an hour. At high metal concentrations, up-regulation of the genes for metal efflux systems occurs within minutes. Here, we investigates the changes in the bacterial proteome accompanying these genetic and physiological events after 1.5 cell duplications, which took 3 hours. To that end, C. metallidurans CH34 and its plasmid-free derivative, AE104, were challenged either with a toxic metal mix or were cultivated under metal-starvation conditions, followed by bottom-up proteomics. When metal-shocked or -starved cells were compared with their respective controls, 3 540 proteins changed in abundance, with 76% appearing in one, but not the other, condition; the remaining 24% were up- or down-regulated. Metal-shocked C. metallidurans strains had adjusted their proteomes to combat metal stress. The most prominent polypeptides were the products of the plasmid-encoded metal-resistance determinants in strain CH34, particularly the CzcCBA transenvelope efflux system. Moreover, the influence of antisense transcripts on the proteome was also revealed. In one specific example, the impact of an asRNA on the abundance of gene products could be demonstrated and this yielded new insights into the function of the transmembrane efflux complex ZniCBA under conditions of metal starvation.

Biosorption of Pb2+, Cd2+ and Zn2+ from aqueous solutions by Agrobacterium tumefaciens S12 isolated from acid mine drainage

Heavy metal pollution is a global environmental issue, and microorganisms play a crucial role in the bioremediation of heavy metal-contaminated wastewater. The study isolated heavy metal-resistant bacterium and observed their absorption ability toward Pb2+, Cd2+ and Zn2+. We isolated Agrobacterium tumefaciens S12 from acid mine drainage. The various factors influencing its adsorption performance, including pH, biomass dosage, initial metal ion concentration, and adsorption temperature, were investigated in detail. Chemisorption controls the adsorption rate due to the results better fitted by pseudo-second order kinetics. The maximum adsorption capacities of Pb2+, Cd2+ and Zn2+ on A. tumefaciens S12 were 234, 58 and 51 mg g−1 at 30 °C from Langmuir isotherm, respectively. The adsorption processes for the three heavy metal ions were spontaneous and exothermic in nature. In bimetallic systems, biosorption of Pb2+ ions was preferential to that of Cd2+ and Zn2+. Furthermore, scanning electron microscopy coupled to energy dispersive spectroscopy, Fourier-transform infrared spectra and X-ray photoelectron spectroscopy analysis demonstrated that the adsorption mechanisms include ion-exchange, complexation interaction between the heavy metal ions and the functional groups on the surface of biomass. The obtained results indicated that A. tumefaciens S12 can be applied as an efficient biosorbent in bioremediation technology to sequestrate heavy metal ions from aqueous solution.

Multi-metal resistance and antibiotic susceptibility of biofilm forming bacteria isolated from Kuzhikandam Creek in Kochi, southwest part of India

The purpose of this work was to characterize and identify the bacteria isolated from highly polluted locations that could potentially be able to withstand extremely toxic heavy metals. The study area selected for bacterial isolation from sediment samples was Kuzhikandam Creek, a tributary of the Periyar River and one of the world’s most hazardous hotspots, located in Kochi’s Eloor industrial region. Heavy metal analysis of chromium, copper, and lead in sediment samples was performed, and the results showed that the concentrations were greater than permissible limits. Several metal-resistant bacteria were isolated from sediments, which, upon further screening in solid media at different concentrations of chromium, copper, and lead, found three highly resistant species (S1B1, S2B2, and S3B3), one from each site. The phenotypic and biochemical characterization of these bacteria was examined using standard procedures. The ability of these species to generate biofilm was examined using methods like the crystal violet assay (qualitative assessment) and also using the scanning electron microscope. The antibiotic susceptibility of these species was tested with six different antibiotics, which are used in various disease treatments. These isolates, sequenced using the 16S rRNA Sanger dideoxy method, have been identified as Staphylococcus arlettae, Bacillus paramycoides, and Cellulosimicrobium funkei.

Development of polyfunctionalized biochar modified with manganese oxide and sulfur for immobilizing Hg(II) and Pb(II) in water and soil and improving soil health

Mercury (Hg) and lead (Pb) pose significant risks to human health due to their high toxicity and bioaccumulative properties. This study aimed to develop a novel biochar composite (HMB-S), polyfunctionalized with manganese dioxide (α-MnO2) and sulfur functional groups, for the effective immobilization of Hg(II) and Pb(II) from contaminated environments. HMB-S demonstrated superior adsorption capacities of 190.1 mg/g for Hg(II) and 259.9 mg/g for Pb(II), which significantly surpasses the capacities of unmodified biochar (HB) and biochar functionalized solely with Mn (HMB). Mechanistic studies revealed that the immobilization of these metals by HMB-S involved ion exchange, mineral precipitation, surface complexation, and electrostatic interactions. In soil incubation experiments, HMB-S significantly decreased the levels of extractable Hg(II) and Pb(II) compared to the control, reducing the mobility of these metals and converting 17 % of Hg(II) and 26 % of Pb(II) into less bioavailable residual forms. Pot experiments confirmed that all tested biochar materials (HB, HMB, and HMB-S) promoted spinach growth in contaminated soils, with HMB-S being the most effective at lowering Hg(II) and Pb(II) uptake by plants. Additionally, analysis of soil microbial communities indicated that HMB-S altered community composition and increased the relative abundance of metal-resistant bacteria. These findings highlight the potential of polyfunctionalized biochar HMB-S as an effective remediation strategy for Hg and Pb contamination in soil and aqueous environments.

Culture-based and molecular investigation of antibiotic and metal resistance in a semi-arid agricultural soil repeatedly amended with urban sewage sludge

Unsustainable agricultural intensification and climate change effects have caused chronic soil depletion in most arid and semi-arid croplands. As such, the land application of urban sewage sludge (USS) has been regulated in several countries as an alternative soil conditioner with recycling benefits. However, the risks of multi-contamination have made its agricultural reuse debatable. Accordingly, this study explored the long-term the impact of repetitive USS applications with increasing rates (0, 40, 80, and 120 t ha−1 year−1) on a sandy soil properties. A special focus was on the spread of antibiotic-resistant bacteria, metal-resistant bacteria and corresponding resistance genes in soil (ARB, MRB, ARGs and MRGs, respectively). The outcomes showed a dose-dependent variation of different soil parameters including the increase of heavy metal content and total heterotrophic bacteria (THB) up to the highest sludge application rate. Besides, the two last sludge lots applied in fall 2019 and 2020 contained cultivable ARB for all addressed antibiotics at much higher counts than in corresponding treated soils. Interestingly, the average index of antibiotic resistance (ARB/THB) increased in the USS used in fall 2020 compared to 2019 (from 6.2% to 9.4%). This indicates that factors such as fluctuations in wastewater quality, treatments operations, and extensive antibiotic use following the outbreak of the COVID-19 pandemic in early 2020 could have caused this variation. The molecular assessment of bacterial resistance resulted in the identification of three ARGs (mefA, sul1 and sul2), one MRG (czcA) and one integron (intI1). This might have implications on resistance co-selection, which can pose a threat to human health via contaminated crops.

Inoculation of multi-metal-resistant Bacillus sp. to a hyperaccumulator plant Sedum alfredii for facilitating phytoextraction of heavy metals from contaminated soil

Co-contamination of soil by multiple heavy metals is a significant global challenge. An effective strategy to address this issue involves using hyperaccumulators such as Sedum alfredii (S. alfredii). The efficiency of phytoremediation can be improved by supplementing with plant growth-promoting bacteria (PGPB). However, bacteria resources of PGPB resistant to multi-heavy metal contamination are still lacking. This study focused nine different strains of Bacillus and screened for resistance to heavy metals including cadmium (Cd), zinc (Zn), copper (Cu), and lead (Pb). A superior strain, Bacillus subtilis PY79 (B. subtilis), showed tolerance for all tested metals. Inoculation with B. subtilis in the rhizosphere of S. alfredii increased the accumulation of Cd, Zn, Cu, and Pb by 88.02%, 58.99%, 90.22%, and 54.97% in the plant shoots after 30 days respectively. B. subtilis application lowered the pH of the rhizosphere soil, thereby increasing the bioavailability of nutrients and heavy metals. Furthermore, B. subtilis helped S. alfredii recruit PGPB and heavy metal-resistant bacteria such as Edaphobacter, Niastella, and Chitinophaga, enhancing the growth and phytoremediation efficiency. Moreover, inoculation with B. subtilis not only upregulated genes of the ABC, HMA, ZIP, and MTP families involved in the translocation and detoxification of heavy metals but also increased the secretion of antioxidants within the cells. These findings indicate that B. subtilis enhances the tolerance, uptake, and translocation of heavy metals in S. alfredii, offering valuable insights for the phytoremediation of multi-metal-contaminated soils.

Identification and isolation of efficient phenol-degrading and heavy metal-resistant bacteria from seasonal catchments of the Lut Desert

ABSTRACT The present study was conducted to isolate and identify a phenol-degrading bacterial strain resistant to cadmium obtained from seasonal catchments of the Lut Desert, Iran. Additionally, optimal conditions affecting biological phenol degradation, including pH, temperature, salinity, and carbon-to-nitrogen ratio, were determined using the Taguchi method, and the ability of the purified strain to degrade phenol in different concentrations was investigated. Isolated bacterium strain Bacillus cereus LD-1, capable of phenol degradation and cadmium tolerance, could tolerate and degrade phenol up to a concentration of 1,500 mg/L. All optimized factors except carbon-to-nitrogen ratio had a significant effect on the rate of phenol biodegradation. Among the selected factors, based on the effect size, pH had the highest impact (10.02), followed by salinity (6.16), temperature (5.61), and C:N ratio (2.55) on phenol biodegradation. The optimal conditions for phenol biodegradation were determined as pH of 8, temperature of 30 °C, salinity of 0 g/L, and C:N ratio of 100:30. Under optimal conditions, 80.57% of phenol was decomposed by the LD-1 strain. Considering the high ability of the isolated strain for phenol degradation in the presence of 100 mg/L cadmium, LD-1 can be applied in the biological treatment of phenolic effluents contaminated with heavy metals.

Taxonomic and functional characterization of biofilms from a photovoltaic panel reveals high genetic and metabolic complexity of the communities.

Biofilms are complex microbial cell aggregates that attach to different surfaces in nature, industrial environments, or hospital settings. In photovoltaic panels (PVs), biofilms are related to significant energy conversion losses. In this study, our aim was to characterize the communities of microorganisms and the genes involved in biofilm formation. In this study, biofilm samples collected from a PV system installed in southeastern Brazil were analyzed through shotgun metagenomics, and the microbial communities and genes involved in biofilm formation were investigated. A total of 2030 different genera were identified in the samples, many of which were classified as extremophiles or producers of exopolysaccharides. Bacteria prevailed in the samples (89%), mainly the genera Mucilaginibacter, Microbacterium, Pedobacter, Massilia, and Hymenobacter. The functional annotation revealed >12 000 genes related to biofilm formation and stress response. Genes involved in the iron transport and synthesis of c-di-GMP and c-AMP second messengers were abundant in the samples. The pathways related to these components play a crucial role in biofilm formation and could be promising targets for preventing biofilm formation in the PV. In addition, Raman spectroscopy analysis indicated the presence of hematite, goethite, and ferrite, consistent with the mineralogical composition of the regional soil and metal-resistant bacteria. Taken together, our findings reveal that PV biofilms are a promising source of microorganisms of industrial interest and genes of central importance in regulating biofilm formation and persistence.

Bioremediation of Arsenic and Cadmium by Metal-Resistant Bacteria in Spinach

Bioremediation of Arsenic and Cadmium by Metal-Resistant Bacteria in Spinach

Study of Multiple Metal Resistant Citrobacter sp. Isolated From Industrial Effluent

The pollution of the environment with toxic heavy metals is spreading throughout the world along with industrial progress. Microbe related technologies may provide an alternative or addition to conventional method of metal removal or metal recovery. The present study deals with isolation, identification and characterization of heavy metal resistant bacteria from industrial effluent. a total58 isolates were screened for heavy metal resistant from industrial effluent. The GOZPRN isolate show multiple metal resistant and antibiotic resistances. On the basis of morphological, biochemical, partial 16S rRNA gene sequencing revealed that this isolates belongs to Citrobacter sp.. The isolate showed optimum growth at 30°C and pH 7.0. This isolate was found to be resistant to nickel (Ni), lead (Pb), zinc (Zn), Chromium (Cr). The minimal tolerance concentration (MTC) of this isolate against Cr, Ni, Pb, and Zn was 2.8 mM, 80 mM, 800 mM, and 500 mM respectively. It also exhibited resistance against tetracycline. This Citrobacter Sp. has potential to be useful for the bioremediation of heavy metals.

Isolation of Multidrug-Resistant Bacteria from Raw Hides, Salted Hides, and Tannery Wastewater and Their Heavy Metal (Cr) Tolerance

Numerous leather products are created from cattle hides and skins. However, the processing of these products can release toxic heavy metals, including chromium into the environment, leading to health hazards and environmental pollution. This study aims to isolate and identify multidrug-resistant bacteria from rawhide, salted hides, and tanneries in different areas of the Savar region in Dhaka City, Bangladesh. The secondary objective is to determine the heavy metal tolerance and Minimum Inhibitory Concentration (MIC) of Cr against all isolated bacteria. The study found 206 bacterial isolates from three areas: Polashbari Kathaltola, Polashbari Bazar, and Savar Hemaythpur. Rawhide yielded 100 (48.54%) bacterial isolates, salted hide yielded 80(38.83%) isolates, and tannery wastewater yielded only 26 (12.62%) isolates. Further, Bacillus spp. (60) was the most common isolated bacteria. The other identified bacteria were Pseudomonas spp. (46), Staphylococcus spp. (40), Proteus spp. (40), and Escherichia coli (20). The isolated strains showed multidrug resistance, with Staphylococcus spp. Being highly resistant to Erythromycin (100%), followed by Trimethoprim (95%) and Tetracycline (88%). Pseudomonas spp. Were highly resistant to Azithromycin (100%) and Gentamycin (100%). The MIC and the MIC breakpoint determined the screening and evaluation of Cr tolerance against bacteria, and among the isolated bacterial isolates, Bacillus spp. showed a MIC breakpoint of 600 ppm (11.52mM) for Cr tolerance. The isolated heavy metal-resistant bacteria are useful in the bioremediation process and can aid in recovering and removing heavy metals from environmental effluents, thus preventing adverse effects on humans and animals. The government and leather companies should take legal responsibility for proper leather processing to ensure a preventative approach for safe public health. Otherwise, carcinogenic heavy metals can cause cancer in humans.

Omics technology draws a comprehensive heavy metal resistance strategy in bacteria.

The rapid industrial revolution significantly increased heavy metal pollution, becoming a major global environmental concern. This pollution is considered as one of the most harmful and toxic threats to all environmental components (air, soil, water, animals, and plants until reaching to human). Therefore, scientists try to find a promising and eco-friendly technique to solve this problem i.e., bacterial bioremediation. Various heavy metal resistance mechanisms were reported. Omics technologies can significantly improve our understanding of heavy metal resistant bacteria and their communities. They are a potent tool for investigating the adaptation processes of microbes in severe conditions. These omics methods provide unique benefits for investigating metabolic alterations, microbial diversity, and mechanisms of resistance of individual strains or communities to harsh conditions. Starting with genome sequencing which provides us with complete and comprehensive insight into the resistance mechanism of heavy metal resistant bacteria. Moreover, genome sequencing facilitates the opportunities to identify specific metal resistance genes, operons, and regulatory elements in the genomes of individual bacteria, understand the genetic mechanisms and variations responsible for heavy metal resistance within and between bacterial species in addition to the transcriptome, proteome that obtain the real expressed genes. Moreover, at the community level, metagenome, meta transcriptome and meta proteome participate in understanding the microbial interactive network potentially novel metabolic pathways, enzymes and gene species can all be found using these methods. This review presents the state of the art and anticipated developments in the use of omics technologies in the investigation of microbes used for heavy metal bioremediation.

First report on in-depth genome and comparative genome analysis of a metal-resistant bacterium Acinetobacter pittii S-30, isolated from environmental sample.

A newly isolated bacterium Acinetobacter pittii S-30 was recovered from waste-contaminated soil in Ranchi, India. The isolated bacterium belongs to the ESKAPE organisms which represent the major nosocomial pathogens that exhibit high antibiotic resistance. Furthermore, average nucleotide identity (ANI) analysis also showed its closest match (>95%) to other A. pittii genomes. The isolate showed metal-resistant behavior and was able to survive up to 5 mM of ZnSO4. Whole genome sequencing and annotations revealed the occurrence of various genes involved in stress protection, motility, and metabolism of aromatic compounds. Moreover, genome annotation identified the gene clusters involved in secondary metabolite production (biosynthetic gene clusters) such as arylpolyene, acinetobactin like NRP-metallophore, betalactone, and hserlactone-NRPS cluster. The metabolic potential of A. pittii S-30 based on cluster of orthologous, and Kyoto Encyclopedia of Genes and Genomes indicated a high number of genes related to stress protection, metal resistance, and multiple drug-efflux systems etc., which is relatively rare in A. pittii strains. Additionally, the presence of various carbohydrate-active enzymes such as glycoside hydrolases (GHs), glycosyltransferases (GTs), and other genes associated with lignocellulose breakdown suggests that strain S-30 has strong biomass degradation potential. Furthermore, an analysis of genetic diversity and recombination in A. pittii strains was performed to understand the population expansion hypothesis of A. pittii strains. To our knowledge, this is the first report demonstrating the detailed genomic characterization of a heavy metal-resistant bacterium belonging to A. pittii. Therefore, the A. pittii S-30 could be a good candidate for the promotion of plant growth and other biotechnological applications.

Isolation and Characterization of Heavy Metal-Tolerant Bacterial Isolates from Industrial Effluents in Uttar Pradesh, India

Industrial activities over the past century have significantly increased human exposure to pollutants such as heavy metals. Industrial emissions of heavy metals, which are carcinogenic, mutagenic and toxic, contaminate natural water supplies and the agricultural environment. Due to the high concentration of heavy metals in industrial effluents, the bacteria present there naturally develop resistance to heavy metals. The aim of this study is to isolate and characterize bacteria resistant to heavy metal, lead (Pb), copper (Cu), chromium (Cr), cadmium (Cd), and nickel (Ni) from sites contaminated by industrial effluents in Uttar Pradesh, India. A total of 58 bacterial isolates were isolated from 9 samples according to their various morphological parameters and 32 isolates were found positive for all heavy metals, which revealed that samples contained metal-resistant bacterial diversity. Two isolates were identified up to species level based on their physiological, biochemical and molecular characterization as Comamonas testosteroni (S4C1) and Bacillus cereus (S5C3). Both isolates are highly resistant to lead (Pb), copper (Cu), chromium (Cr), cadmium (Cd), and nickel (Ni) and they show different MICs against the above heavy metals at different levels. A growth experiment showed that the presence of heavy metals concentration had no discernible impact on the growth rate among the isolates. Gel analysis showed interesting patterns of protein expression were observed in the presence of various heavy metals. MALDI-TOF analysis found that specific proteins (S layer protein, F0F1ATP synthase subunit b, Flagellin, 50S ribosomal protein L4, Molecular chaperone) were overexpressed in the presence of heavy metals. As a result, identifying the heavy metal resistance bacteria and their proteins study could be useful as a preliminary investigation for the development of prospective bioremediation agents of potentially hazardous waste treatment technology.

A gold speciation that adds a second layer to synergistic gold-copper toxicity in Cupriavidus metallidurans.

The metal-resistant bacterium Cupriavidus metallidurans occurs in metal-rich environments. In auriferous soils, the bacterium is challenged by a mixture of copper ions and gold complexes, which exert synergistic toxicity. The previously used, self-made Au(III) solution caused a synergistic toxicity of copper and gold that was based on the inhibition of the CupA-mediated efflux of cytoplasmic Cu(I) by Au(I) in this cellular compartment. In this publication, the response of the bacterium to gold and copper was investigated by using a commercially available Au(III) solution instead of the self-made solution. The new solution was five times more toxic than the previously used one. Increased toxicity was accompanied by greater accumulation of gold atoms by the cells. The contribution of copper resistance determinants to the commercially available Au(III) solution and synergistic gold-copper toxicity was studied using single- and multiple-deletion mutants. The commercially available Au(III) solution inhibited periplasmic Cu(I) homeostasis, which is required for the allocation of copper ions to copper-dependent proteins in this compartment. The presence of the gene for the periplasmic Cu(I) and Au(I) oxidase, CopA, decreased the cellular copper and gold content. Transcriptional reporter gene fusions showed that up-regulation of gig, encoding a minor contributor to copper resistance, was strictly glutathione dependent. Glutathione was also required to resist synergistic gold-copper toxicity. The new data indicated a second layer of synergistic copper-gold toxicity caused by the commercial Au(III) solution, inhibition of the periplasmic copper homeostasis in addition to the cytoplasmic one.IMPORTANCEWhen living in auriferous soils, Cupriavidus metallidurans is not only confronted with synergistic toxicity of copper ions and gold complexes but also by different gold species. A previously used gold solution made by using aqua regia resulted in the formation of periplasmic gold nanoparticles, and the cells were protected against gold toxicity by the periplasmic Cu(I) and Au(I) oxidase CopA. To understand the role of different gold species in the environment, another Au(III) solution was commercially acquired. This compound was more toxic due to a higher accumulation of gold atoms by the cells and inhibition of periplasmic Cu(I) homeostasis. Thus, the geo-biochemical conditions might influence Au(III) speciation. The resulting Au(III) species may subsequently interact in different ways with C. metallidurans and its copper homeostasis system in the cytoplasm and periplasm. This study reveals that the geochemical conditions may decide whether bacteria are able to form gold nanoparticles or not.

Inoculation of heavy metal resistant bacteria alleviated heavy metal-induced oxidative stress biomarkers in spinach (Spinacia oleracea L.)

Most vegetable crops are severely affected by the uptake of heavy metals from the soil. Heavy metals in vegetable bodies generate reactive oxygen species (ROS) that unbalance the antioxidant defense system. This study was initiated to determine the physiological and biochemical characteristics of spinach plants grown on soil contaminated with heavy metals and responding to Bacillus cereus and Bacillus aerius were isolated from soil contaminated with heavy metals. Heavy metal contamination led to a significant reduction in seed germination, seedling biomass, protein, and total nitrogen content of spinach plants grown in contaminated soils compared to control soils. In contrast, a significant increase in the content of metallothioneins and antioxidant enzymes was observed. Plants inoculated with B. cereus and B. aerius significantly reduced the oxidative stress induced by heavy metals by improving seed germination (%), seedling growth, nitrogen, and protein content. The content of metallothioneins and the activities of antioxidant enzymes were reduced in spinach plants grown from seeds inoculated with bacterial strains. In addition, plants inoculated with, B. cereus and B. aerius showed greater stomata opening than plants grown on soil contaminated with heavy metals, whose stomata were almost closed. These results suggested that both bacterial strains enhanced plant growth by reducing oxidative stress caused by metals.

Screening and Identification of Chromium Resistant Bacteria from Poultry Excreta

The occurrence of heavy metal-resistant bacteria in the environment acts as an indicator of heavy metal pollution. The impact of heavy metal contamination in co-selection and proliferation of antimicrobial[1]resistant bacteria is well-documented in existing literature. The present study aims to determine the occurrence of chromium-resistant bacteria (CRB) in poultry feces and to characterize their antimicrobial resistance and biofilm formation ability. 28 CRBs were isolated by inoculating samples on chromium-amended media. 6 of 28 isolates were resistant to a maximum of 1000 ppm chromium. Isolated CRBs also showed varying degrees of resistance to other heavy metals, including Cd, Ni, and Hg. Biofilm formation was observed in 67.8% isolates, of which 60.7% and 7.1% were weak and moderate biofilm former, respectively. All the isolates exhibited sensitivity to Gentamicin, Chloramphenicol, Imipenem, and Amikacin. Only one isolate was multi-drug resistant. In addition, all the isolates possessed chromate reductase gene that confirmed their chromium-reducing activity. Two isolates were identified as Bacillus altituidinis and Brevibcillus parabrevis on the basis of 16s rRNA analysis. Further estimation of chromium-reduction capacity and whole genome analysis will reveal their bioremediation potential.
 Bangladesh J Microbiol, Volume 40, Number 1, June 2023, pp 1-6

Co-occurrence of Heavy Metal and Antibiotics Resistance Traits in Bacteria Isolated from Poultry Droppings and Soil in Badagry, Lagos

Background: Heavy metal and antibiotic resistance are two pressing global concerns affecting the agri-cultural and food sectors. Moreover, heavy metals tend to select antibiotic resistance in the absence of antibiotics. This study aimed to isolate, screen and identify heavy metal-resistant bacteria that can resist multiple antibiotics in agricultural settings. Methods: Using standard cultural techniques, twenty-six heavy metal tolerant bacteria were isolated from poultry droppings and soil samples collected from Lagos State Food Processing Centre located at Badagry, Lagos. The isolates were presumptively identified by their morphological characteristics and subjected to antibiotics sensitivity test using the disc diffusion method. The identities of isolates exhib-iting multi-drug resistance (MDR) among the metal tolerance isolates were authenticated using 16S rRNA gene sequence analysis. Results: All isolates recovered from the soil sample tolerated 3 mM of lead and nickel, while isolates from poultry droppings recorded the least tolerable concentrations of 1 mM and 2 mM of cadmium and lead, respectively. Each isolate exhibited resistance to at least a group of antibiotics phenotypically. Resistance to colistin (42.31%) was the highest among the isolates, closely followed by chlorampheni-col (23.08%), while gentamicin (3.85%) was the lowest among the isolates. However, six isolates were shown to be MDR strain, and they were identified as Bacillus pumilus, Bacillus cereus, Brevundimonas naejangsanensis, Pseudochrobactrum asaccharolyticum, Pseudochrobactrum saccharolyticum and Lysinibacillus xylanilyticus. Conclusion: This study further draws attention to the increasing dual resistance of bacteria to heavy metals and antibiotics, which may hinder the fight against antimicrobial resistance in agricultural set-tings

Metalloproteomics: Unraveling the Metal Binding Proteins of Diverse Metal-Resistant Bacteria

The release of metals into the environment raises serious concerns about their harmful effects on both the wildlife and human health. The biosphere is experiencing with the pervasive presence of heavy metal pollutants such as arsenic (As), cadmium (Cd), mercury (Hg), lead (Pb), chromium (Cr), copper (Cu) and nickel (Ni), which pose significant environmental challenges. While certain metals are essential for regulating fundamental metabolic processes and upholding the overall physiology of microorganisms, excessive exposure to heavy metals can be detrimental to their survival and function. As a result of their remarkable adaptability, microorganisms, particularly bacteria such as Pseudomonas fluorescens, Escherichia coli, Serratia marcescens, Bacillus cereus and Alcaligenes sp., have evolved sophisticated defence mechanisms to combat the stress caused by heavy metals. One such process is the creation of metal-binding proteins (MBPs), which may bind and sequester metals, thus significantly lowering their toxicity in bacteria. Metalloproteomics, a subfield of metallomics, focuses on the discovery and characterization of such metal-binding proteins (MBPs) in metal-resistant bacteria, resulting in the opening of the doors for innovative bioremediation techniques and therapeutic treatments against bacterial diseases. This review explores the intriguing world of MBPs in metal-resistant bacteria and emphasizes their significant role in metal resistance, detoxification and homeostasis. Furthermore, metallochaperones in bacteria have been extensively studied using the metalloproteomic methodologies and techniques utilized in metal-binding proteins. This study also provides useful information on the interactions between these metallochaperones and different MBPs, which advances our understanding of how bacteria respond to exposure to such heavy metals.

A novel Zr-P-modified nanomagnetic herbal biochar immobilized Cd and Pb in water and soil and enhanced the relative abundance of metal-resistant bacteria: Biogeochemical and spectroscopic investigations to identify the governing factors and potential mechanisms

Remediation of toxic metals contaminated water and soil using engineered biochar is of great concern. This study introduces a novel zirconium-phosphate-modified nanomagnetic biochar (ZMBC) synthesized from traditional Chinese herbal residues as a potential adsorbent for remediation of Cd2+ and Pb2+ contaminated water and soil. The impact of co-existing ions, ionic strength, metal concentrations, pH, and contact time on the adsorption/immobilization efficiency/mechanisms of ZMBC for Cd2+ and Pb2+ in water and soil were investigated together with the induced changes in soil bacterial community for the first time. The governing factors and potential mechanisms for the interaction between metals and ZMBC have been investigated using biogeochemical, microscopic, and spectroscopic techniques. The adsorption capacity of ZMBC for Pb2+ (357.1 mg g−1) and Cd2+ (136.2 mg g−1) was significantly higher than that of pristine biochar (BC) and nanomagnetic biochar (MBC) (<5 mg g−1). The adsorption behavior for Pb2+ and Cd2+ followed the pseudo-second-order, intra-particle diffusion and Langmuir model, and was minimally affected by ionic strength. Co-existence of Ca2+, Cu2+ and Zn2+ ions at lower concentrations (<10 mg L–1) promoted the adsorption of Pb2+ but inhibited it at higher concentrations (50–200 mg L–1). Conversely, the co-existence of those ions at 10–200 mg L–1, particularly Cu2+ and Zn2+ significantly inhibited Cd2+ adsorption. Adsorption of Pb2+ and Cd2+ on ZMBC was dominated by functional group complexation, co-precipitation, metal-π electronic coordination, and ion exchange. Addition of ZMBC to the contaminated soil altered the mobile fraction of Cd2+ and Pb2+ to the residual fractions and thus significantly reduced the DTPA-extractable Pb2+ by 51.3% and Cd2+ by 56.1%, and also reduced the Cd and Pb in the wheat roots (by 64.0% and 36.1%, respectively) and shoots (by 73.5% and 62.2%, respectively), as compared to the untreated soil. The analysis of the soil 16S rDNA gene showed that the addition of ZMBC increased soil bacteria suitable for bioremediation of Pb2+ and Cd2+ contaminated soil. Those findings conclude that ZMBC can be used as a promising amendment for remediation of water and soils co-polluted with Cd and Pb.