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Members of the high-affinity potassium transporter (HKT) protein family regulate the uptake and homeostasis of sodium and potassium ions, but little research describes their roles in response to abiotic stresses in rapeseed (Brassica napus L.). In this study, we identified and characterized a total of 36 HKT genes from the species comprising the triangle of U model (U-triangle species): B. rapa, B. nigra, B. oleracea, B. juncea, B. napus, and B. carinata. We analyzed the phylogenetic relationships, gene structures, motif compositions, and chromosomal distributions of the HKT family members of rapeseed. Based on their phylogenetic relationships and assemblage of functional domains, we classified the HKT members into four subgroups, HKT1;1 to HKT1;4. Analysis of the nonsynonymous substitutions (Ka), synonymous substitutions (Ks), and the Ka/Ks ratios of HKT gene pairs suggested that these genes have experienced strong purifying selective pressure after duplication, with their evolutionary relationships supporting the U-triangle theory. Furthermore, the expression profiles of BnaHKT genes varies among potassium, phytohormone and heavy-metal treatment. Their repression provides resistance to heavy-metal stress, possibly by limiting uptake. Our results systematically reveal the characteristics of HKT family proteins and their encoding genes in six Brassica species and lay a foundation for further exploration of the role of HKT family genes in heavy-metal tolerance. [ABSTRACT FROM AUTHOR]

Noccaea caerulescens (J. Presl & C. Presl) F. K. Mey. is a heavy metal hyperaccumulator exhibiting extreme tolerance to various environmental stresses. To date, the functional role of Ca2+-binding protein in this plant is largely unknown. To investigate the function of calmodulins (CaMs) in N. caerulescens , CaM2 , a Ca2+ sensor encoding gene, was identified and functionally characterised. Protein structure analysis showed that NcCaM2 contains four classic exchange factor (EF)-hand motifs with high sequence similarity to the CaM proteins from model plant Arabidopsis thaliana L. Tissue specific expression analysis showed that NcCaM2 is constitutively expressed in stems, leaves, and roots. Expression level of NcCaM2 was significantly upregulated under various environmental stimulus, indicating a potential involvement of NcCaM2 in the tolerance to abiotic stresses. The heterologous expression of NcCaM2 in a yeast mutant strain increased the heavy metal tolerance in yeast cells. Furthermore, the constitutive expression of NcCaM2 enhanced the heavy metal tolerance capability of transgenic tobacco (Nicotiana tabacum L.) plants. Our data suggested an important role of NcCaM2 in the responses to environmental stresses and provided a potential target gene to enhance of the ability to hyperaccumulate metals. Noccaea caerulescens (J. Presl & C. Presl) F. K. Mey. is a heavy metal hyperaccumulator exhibiting extreme tolerance to various heavy metal stresses. A Ca2+-binding protein in N. caerulescens has been cloned and functional identified. Our data provides a clue to reveal the adaptation strategy of plants to metalliferous soils. [ABSTRACT FROM AUTHOR]

The Wonderfonteinspruit, South Africa, is highly impacted by a century of gold mining activities. The aim of this study was to investigate the physico-chemical properties of the Wonderfonteinspruit and the receiving Mooi River system, the levels of antimicrobial (metals and antibiotics) resistance characteristics and heterotrophic bacteria levels in these water systems. Various physico-chemical parameters were determined. R2A agar and R2A agar supplemented with antimicrobials were used to enumerate heterotrophic bacteria. Morphologically distinct antimicrobial-resistant isolates were purified and screened for antibiotic susceptibility by a disc diffusion method. Selected isolates were identified, and minimum inhibitory concentration ranges determined. Among the antimicrobial resistant isolates, 87% were resistant to at least one antibiotic. Of these, almost 50% were resistant to more than 3 antibiotic classes. A large proportion was resistant to all 7 antibiotics tested. Phyla detected were Proteobacteria, Firmicutes and Bacteriodetes. High MIC levels for metals and antibiotics were detected among all the genera. Results demonstrate potential impacts of physico-chemical properties on levels of antimicrobial-resistant bacteria. Metal-resistant bacteria were also resistant to multiple antibiotics, suggesting that metal pollution from mining may be responsible for co-selection and maintenance of antibiotic-resistant bacteria in this aquatic system. [ABSTRACT FROM AUTHOR]

Members of the high-affinity potassium transporter (HKT) protein family regulate the uptake and homeostasis of sodium and potassium ions, but little research describes their roles in response to abiotic stresses in rapeseed (Brassica napus L.). In this study, we identified and characterized a total of 36 HKT genes from the species comprising the triangle of U model (U-triangle species): B. rapa, B. nigra, B. oleracea, B. juncea, B. napus, and B. carinata. We analyzed the phylogenetic relationships, gene structures, motif compositions, and chromosomal distributions of the HKT family members of rapeseed. Based on their phylogenetic relationships and assemblage of functional domains, we classified the HKT members into four subgroups, HKT1;1 to HKT1;4. Analysis of the nonsynonymous substitutions (Ka), synonymous substitutions (Ks), and the Ka/Ks ratios of HKT gene pairs suggested that these genes have experienced strong purifying selective pressure after duplication, with their evolutionary relationships supporting the U-triangle theory. Furthermore, the expression profiles of BnaHKT genes varies among potassium, phytohormone and heavy-metal treatment. Their repression provides resistance to heavy-metal stress, possibly by limiting uptake. Our results systematically reveal the characteristics of HKT family proteins and their encoding genes in six Brassica species and lay a foundation for further exploration of the role of HKT family genes in heavy-metal tolerance.

Mine tailings represent a great environmental concern due to their high contents of heavy metals. Cultivation analysis of microbiota of Tarnowskie Góry (Poland) mine tailing showed the occurrence of bacteria with colony-forming units as low as 5.7 × 104 per one gram of dried substrate. Among 110 bacterial isolates identified by a combination of MALDI-TOF mass spectrometry and 16S rRNA gene sequencing, phylum Actinobacteria was dominant, followed by Firmicutes and Proteobacteria. Extremely high levels of heavy-metal resistance were observed in Arthrobacter spp., particularly for zinc (500 mg/L), lead (1500 mg/L), and cadmium (1000 mg/L). On the other hand, Staphylococcus spp. showed high tolerance to several antibiotics tested, especially ampicillin, partly due to blaZ gene presence. Due to the occurrence of antibiotic-resistant bacteria, mine tailings are not the cause of heavy-metal contamination only, but also a source of antibiotic-resistant bacteria and thus may represent a serious risk for public health. [ABSTRACT FROM AUTHOR]

Certain industrial chemicals accumulate in the environment due to their recalcitrant properties. Bioremediation uses the capability of some environmental bacteria to break down these chemicals and attenuate the pollution. One such bacterial strain, designated Pvy, was isolated from sediment samples from a lagoon in Romania located near an oil refinery due to its capacity to degrade dibenzofuran (DF). The genome sequence of the Pvy strain was obtained using an Oxford Nanopore MiniION platform. According to the consensus 16S rRNA gene sequence that was compiled from six 16S rRNA gene copies contained in the genome and orthologous average nucleotide identity (OrthoANI) calculation, the Pvy strain was identified as Pseudomonas veronii, which confirmed the identification obtained with the aid of MALDI-TOF mass spectrometry and MALDI BioTyper. The genome was analyzed with respect to enzymes responsible for the overall biodegradative versatility of the strain. The Pvy strain was able to derive carbon from naphthalene (NP) and several aromatic compounds of natural origin, including salicylic, protocatechuic, p-hydroxybenzoic, trans-cinnamic, vanillic, and indoleacetic acids or vanillin, and was shown to degrade but not utilize DF. In total seven loci were found in the Pvy genome, which enables the strain to participate in the degradation of these aromatic compounds. Our experimental data also indicate that the transcription of the NP-dioxygenase a-subunit gene (ndoB), carried by the plasmid of the Pvy strain, is inducible by DF. These features make the Pvy strain a potential candidate for various bioremediation applications [ABSTRACT FROM AUTHOR]

Antibiotic resistance (AR) in the environment is a growing and global concern for public health, and intrinsic AR from pristine sites untouched by pharmaceutical antibiotics is not commonly studied. Forty aerobic bacteria were isolated from water and sediment samples of hot springs in South Africa. Resistance against ten antibiotics (carbenicillin, gentamicin, kanamycin, streptomycin, tetracycline, chloramphenicol, ceftriaxone, co-trimoxazole, nalidixic acid and norfloxacin) was tested using a standard disk diffusion assay. Resistance to one or two antibiotics were equally found in 37.5%, while the remaining 22% showed complete sensitivity. Intermediate resistance was found for ceftriaxone (52.5%), nalidixic acid (37.5%) and carbenicillin (22.5%), while low levels of resistance were observed for streptomycin (5%) and kanamycin (2.5%), and total sensitivity towards the other antibiotics. Twenty-nine isolates were also tested against eight different heavy-metal salts (Al, Cr, Cu, Fe, Hg, Mn, Ni and Pb) at 10 and 40 mM. All isolates were tolerant and able to grow on ≥2 heavy-metal salts at both concentrations. No association was observed between AR and heavy metal tolerance (HMT). Based on the relatively low AR levels, hot spring sites are pristine environments reflecting baseline levels for comparison to other potentially contaminated groundwater sites. Image 1 • Hot spring bacteria were tested against 10 antibiotics and 8 heavy metal salts. • Resistance found against ceftriaxone>nalidixic acid>carbenicillin. • All isolates grew on ≥2 heavy-metal salts at 10 and 40 mM concentrations. • Low antibiotic resistance in pristine sites may reflect baseline antibiotic resistance levels. Antibiotic resistance (AR) in the environment is a growing and global concern for public health. Based on the relatively low AR levels, hot spring sites are pristine environments reflecting baseline levels for comparison to other potentially contaminated sites. [ABSTRACT FROM AUTHOR]

A field survey of herbaceous plants growing on the Huice lead (Pb)–zinc (Zn) mining area in Yunnan, China was conducted to identify species accumulating concentrations of cadmium (Cd), Pb, and Zn. In total, 200 plant samples of 112 species from 34 families were collected. At the same time, 200 soil samples were collected. Based on Cd, Pb, and Zn tolerance and growth, wildOxyria sinensisHemsl. was chosen as a primary pioneer plant. Then, to confirm ifOxyria sinensisHemsl. may be used as a pioneer plant, the tolerance to Cd, Pb, and Zn and growth of two ecotypes (mining-area ecotype and non-mining-area ecotype)Oxyria sinensisHemsl. were studied further with pot experiments. In 10 samples of wildOxyria sinensisHemsl. in the Huice lead–zinc mine, concentrations of Cd, Pb, and Zn in the soil did not correlate with those in the root (P> 0.05) and shoot (P> 0.05), respectively. Correlations between Cd concentrations in root and shoot were not observed (P> 0.05), whereas those of Pb and Zn were observed (P< 0.05). Both the enrichment coefficient and translocation factor were <1 for Cd, Pb, and Zn for the wildOxyria sinensisHemsl. In the two ecotypes ofOxyria sinensisHemsl., in pot experiments, the treatment concentrations of Cd, Pb, and Zn did not correlate (P> 0.05) with concentrations of Cd, Pb, and Zn in root and shoot. Significant correlations between the concentrations of Cd, Pb, and Zn in root (P< 0.01) and shoot (P< 0.05) were observed in the two ecotypes. Both enrichment coefficient and translocation factors were <1 for Cd, Pb, and Zn in the two ecotypes, respectively. Treatment concentrations of Cd, Pb, and Zn did not significantly correlate (P> 0.05) with plant height and crowns of the two ecotypes. Treatment concentrations of Pb and Zn did not correlate (P> 0.05) with the biomass of the two ecotypes, whereas that of Cd related significantly to biomass in the two ecotypes.Oxyria sinensisHemsl. was suggested to utilize a tolerant strategy to heavy metals (i.e., exclusion). It was a pioneer plant and will be used in restoration of a vegetation cover in a Pb–Zn mine after further research in tolerant mechanisms and restoration ability are conducted. [ABSTRACT FROM AUTHOR]

Microorganisms have adapted intricate signal transduction mechanisms to coordinate tolerance to toxic levels of metals, including two-component regulatory systems (TCRS). In particular, both cop and czc operons are regulated by TCRS; the cop operon plays a key role in bacterial tolerance to copper, whereas the czc operon is involved in the efflux of cadmium, zinc, and cobalt from the cell. Although the molecular physiology of heavy metal tolerance genes has been extensively studied, their evolutionary relationships are not well-understood. Phylogenetic relationships among heavy-metal efflux proteins and their corresponding two-component regulatory proteins revealed orthologous and paralogous relationships from species divergences and ancient gene duplications. The presence of heavy metal tolerance genes on bacterial plasmids suggests these genes may be prone to spread through horizontal gene transfer. Phylogenetic inferences revealed nine potential examples of lateral gene transfer associated with metal efflux proteins and two examples for regulatory proteins. Notably, four of the examples suggest lateral transfer across major evolutionary domains. In most cases, differences in GC content in metal tolerance genes and their corresponding host genomes confirmed lateral gene transfer events. Three-dimensional protein structures predicted for the response regulators encoded by cop and czc operons showed a high degree of structural similarity with other known proteins involved in TCRS signal transduction, which suggests common evolutionary origins of functional phenotypes and similar mechanisms of action for these response regulators. [ABSTRACT FROM AUTHOR]

Abstract: Bacterial strains from Zn–Pb mine tailings were isolated by trapping with Anthyllis vulneraria, a legume-host suitable for mine substratum phytostabilisation. Sequence analysis of the 16S rRNA gene and three housekeeping genes (atpD, dnaK and recA) showed that they were related to those of the genus Aminobacter. DNA–DNA relatedness of representative isolates supported the placement of novel strains in Aminobacter as a new species. Phenotypic data emphasize their differentiation from the other related species of Aminobacter and Mesorhizobium. Aminobacter isolates exhibited nodA sequences tightly related with M. loti as the closest nodA relative. By contrast, their nodA sequences were highly divergent from those of M. metallidurans, another species associated with A. vulneraria that carries two complete copies of nodA. Therefore, the novel bacterial strains efficient on A. vulneraria represented the first occurrence of legume symbionts in the genus Aminobacter. They represent a new species for which the name Aminobacter anthyllidis sp. nov. is proposed (type strain STM4645T =LMG26462T =CFBP7437T). [Copyright &y& Elsevier]

Abstract: Many lichens can cope with heavy-metal stress, however, the mechanisms of lichen tolerance are still not fully understood. Some lichen secondary metabolites (depsides and depsidones), produced in lichens by the fungal symbiont and accumulated on the outer surface of its hyphae, are supposed to play an important role in the extracellular immoblilization of heavy metals. Lichen photobionts (algal partners in the symbiosis), although surrounded by the mycobiont hyphae, may also accumulate high amounts of trace metals. This can lead to physiological disruptions and morphological damage in algal cells and hence affect the lichen physiological status. We hypothesized that lichen species/specimens living in heavily polluted sites and showing HM tolerance possess a higher content of secondary metabolites than those living in unpolluted sites. Hence, their photobionts can be better protected from the excess of metal ions and need to produce less metal-complexing phytochelatins (PCn) to combat metal toxicity. Specimens of Hypocenomyce scalaris, Cladonia furcata and Lepraria spp. sampled from Zn/Pb-polluted and control sites were compared for the accumulation of Zn/Pb and secondary metabolites, as well as for their production of phytochelatins and glutathione in response to experimental Zn or Pb exposure. Generally, the lichen specimens sampled from the HM-polluted site contained higher amounts of Zn and Pb as well as lichen substances (different depsides and depsidones) than those from the control site. A strong positive correlation was found between the accumulation of secondary metabolites and Zn/Pb accumulation (R 2 =0.98 and 0.63, respectively). For the first time, production of phytochelatins (PC2–3) in response to Zn and Pb (50–200μM) exposure was found in H. scalaris, L. elobata, L. incana and C. furcata. In both species of Lepraria also cysteine, a substrate for GSH and PCs synthesis was detected. The lichens from the polluted site produced under the same exposure conditions, or in response to higher metal concentrations, lower amounts of PCn than those sampled from the control site. It strongly suggests that less Zn and Pb ions reached the photobiont cells of the lichens containing higher amounts of secondary metabolites (lecanoric, fumarprotocetraric, stictic, constictic acids, antranorin). The results obtained support the putative role of some metabolites in heavy-metal tolerance of the lichens inhabiting metal-polluted habitats. [Copyright &y& Elsevier]

Abstract: Estimating the extent of intraspecific variation in sensitivity to contaminant exposure is important in order to explain variation in the outcome of toxicity tests and to predict the effects of chemical stress on natural populations of plants and animals. However, only few studies provide evident data concerning intraspecific variation in life-history traits caused by a differential response to chemical stress. In this study, we compared the life-history response of six laboratory strains of the midge Chironomus riparius to cadmium exposure in a full life-cycle assay. In addition, the level of genetic variation in all strains was measured at five variable microsatellite loci. Several significant differences in life-history traits among the strains were observed in controls and cadmium treatments. The extent of variation among strains was largest at moderate cadmium concentration (0.42mgCd/kgdw). At increased Cd concentrations all strains showed similar levels of high mortality and reduced reproductive success. All strains exhibited considerable levels of genetic impoverishment compared to field populations. Strains with low genetic variation showed reduced fitness in the controls and were more susceptible to Cd exposure. For instance, no reproductive success in the lowest Cd treatment was observed for the strain with the lowest level of genetic diversity. In contrast, this Cd concentration had no negative effects on life-history traits of more variable strains. These results confirm recent findings, that inbreeding and reduced genetic variation influence the reaction of populations towards environmental stress. In addition, we show that the level of genetic variation and inbreeding directly influences the outcome of toxicity tests and contributes to the lack of reproducibility of test results among laboratories. [Copyright &y& Elsevier]

Dehydrin gene transcript could be induced by heavy metals, and some dehydrins possess the ability to bind metals. However, the correlation between dehydrins and heavy-metal stress is unknown. In order to elucidate the contribution of dehydrins to heavy-metal stress tolerance in plants, we cloned two SK2-type dehydrin genes from heavy-metal hyperaccumulator Brassica juncea, and investigated their Cd/Zn tolerance in transgenic plants. Semi-quantitative RT-PCR analysis revealed that BjDHN2/ BjDHN3 expressed in the leaves, stems and roots at a low level and were up-regulated by heavy metals. Antisense BjDHN3 Brassica juncea plants showed more electrolyte leakage and higher malondialdehyde production than the control plants when exposed to heavy metals, and the total amount of metals accumulated in the whole plant was reduced. Transgenic tobacco plants overexpressing BjDHN2/ BjDHN3 showed lower electrolyte leakage and malondialdehyde production than the control plants when exposed to Cd/Zn. These results indicated that BjDHN2/ BjDHN3 enhanced the tolerance for heavy metals by reducing lipid peroxidation and maintaining membrane stability in the plants. [ABSTRACT FROM AUTHOR]

Phytoremediation is a technology for extracting or inactivating pollutants. Echinochloa polystachya [(H. B. K. ) Hitchcock] (Poaceae) is a fast-growing perennial grass that is common in tropical areas and is often found in oil-polluted soils that contain high concentrations of heavy metals. However, its tolerance to heavy metals, and its ability to accumulate them, has yet to be investigated. Here we test the hypothesis that E. Polystachya is able to accumulate high concentrations of cadmium (Cd). Plants were grown hydroponically with different levels of Cd2+ (0, 0. 25, 1, 2, 10, 50, and 100mgL−1), and were found to be tolerant to Cd2+ at all levels. No metal-toxicity symptoms were observed at any Cd2+ level. Root and leaves Cd concentrations were 299±13. 93 and 233±8. 77mgkg−1 (on a dry weight basis), respectively. Scanning electron microscopy showed the inclusion of Cd within the xylem; this result was confirmed by energy dispersive X-ray spectrometry. Leaf tissues also accumulated Cd, especially within the bulliform cells of the epidermis. We conclude that E. Polystachya is a hyperaccumulator of Cd. While data for other metals are not yet available, E. Polystachya shows promise in the phytoextraction of Cd from polluted tropical sites. [Copyright &y& Elsevier]

A sulfate-reducing bacterium, was isolated from a 6 month trained enrichment culture in an anaerobic media containing phosphogypsum as a sulfate source, and, designated strain SA2. Cells of strain SA2 were rod-shaped, did not form spores and stained Gram-negative. Phylogenetic analysis of the 16S rRNA gene sequence of the isolate revealed that it was related to members of the genus Desulfomicrobium (average sequence similarity of 98%) with Desulfomicrobium baculatum being the most closely related (sequence similarity of 99%). Strain SA2 used thiosulfate, sulfate, sulfite and elemental sulfur as electron acceptors and produced sulfide. Strain SA2 reduced sulfate contained in 1–20g/L phosphogypsum to sulfide with reduction of sulfate contained in 2g/L phosphogypsum being the optimum concentration. Strain SA2 grew with metalloid, halogenated and non-metal ions present in phosphogypsum and with added high concentrations of heavy metals (125ppm Zn and 100ppm Ni, W, Li and Al). The relative order for the inhibitory metal concentrations, based on the IC50 values, was Cu, Te>Cd>Fe, Co, Mn>F, Se>Ni, Al, Li>Zn. [Copyright &y& Elsevier]

Festuca rubra cv. Merlin originated from lead and zinc mining areas in the UK has shown multi-metal tolerance ability in laboratory studies. A Type 1 metallothionein (MT) gene mcMT1 was cloned from the copper induced cDNA library of F. rubra cv. Merlin. The mcMT1 cDNA was 492 bp in full length, including a 50 bp 5′ noncoding domain, 213 bp open reading frame and a 211 bp 3′ termination. The coding region of mcMT1 represented a putative 70-amino acid protein with a molecular weight of 7.1 kDa. At each of the N- and C- terminal of the putative protein, six cysteine residues were arranged in a CXCXXXCXCXXXCXC and CXCXXXCXCXXCXC structure, respectively, indicating that it was a Type 1 MT. Southern blot hybridization suggested that there were at least two loci for the mcMT1 gene in the genome. Northern blot analysis showed an enhanced and persistent expression of mcMT1 in the F. rubra, Merlin within 24 h upon copper and cadmium exposure. Functional complementation studies using the Saccharomyces cerevisiae cup1Δ mutant ABDE-1 (metal sensitive) confirmed the functional nature of this mcMT1 gene in sequestering both essential (Cu, Zn) and non-essential metals (Cd, Pb, Cr). [Copyright &y& Elsevier]

summary: This paper is the first to report cadmium tolerance in a dicotyledonous species, Silene vulgaris (Moench.) Garcke. The response to cadmium of five populations originating from one uncontaminated and various heavy‐metal contaminated sites was examined under standardized conditions for three weeks. The tolerance index (TI), based on the mean relative growth rate (R), was determined. Populations originating from cadmium‐contaminated sites showed a distinct tolerance to cadmium. A population from a site enriched only with copper also exhibited a marked co‐tolerance to cadmium. A clear difference in biomass production between the sensitive and tolerant populations was attained at 1 μM cadmium. An optimum biomass production in tolerant populations at a metal concentration higher than in the control, as demonstrated for zinc and copper, could not be established for cadmium. The pattern of cadmium uptake and translocation differed between tolerant and sensitive populations. All tolerant populations accumulated cadmium in the roots and showed some degree of restricted transport to the shoots. The effect of cadmium on the elemental distribution in roots and shoots was population‐independent for some elements (copper, zinc, potassium) and population‐specific for others (phosphorus, magnesium and sodium). The phenomenon of co‐tolerance to cadmium is discussed in relation to possible tolerance mechanisms, especially with regard to metal‐binding compounds (metallothioneins, phytochelatins). [ABSTRACT FROM AUTHOR]

Ten individuals from each of four populations of the moss, Funaria hygrometrica Hedw., were grown on tow copper and two zinc treatments and a control in order to assess tolerance to these metals. Tolerances of two life-history stages (protonemal growth and stem production) showed significant variation among populations, and among individuals within all population that originated on a copper mine. Phenotypic correlations among growth responses to the five experimental treatments were similar in the four populations, but this reflected a greater similarly among the environmental correlations than among the genotypic correlations. There was evidence of positive genetic correlations between growth of control medium and growth on media enriched with copper or zinc. This is contrast to data from flowering plants and fungi, and raises the question of why tolerant individuals are restricted to contaminated sites in nature. [ABSTRACT FROM AUTHOR]

Two substrates saturated with crude oil, a desert soil sample (17.3% oil) and an olive-pomace (plant-based oil sorbent) sample (41% oil) showed effective self-cleaning via their own native microorganisms. The oil in such systems did not gather in one compact layer as it may be expected, but became dispensed as vesicles of varying dimensions connected together with narrow tunnels. Bacteria colonized the oil vesicles but only at the borders between the oil and the watery substrates. Through this architectural arrangement, the cells were capable of absorbing oil through their oil-contact surfaces and oxygen, water and water soluble nutrients through their substrate-contact surfaces. The cells involved were those of indigenous hydrocarbonoclastic bacterial communities. Many of those bacteria also tolerated and removed the amended heavy-metals, Hg2+, Cd2+, Pb2+, AsO 4 3− and AsO 3 3−. In the presence of heavy-metals, some of the bacterial species particularly of the pseudomonads exhibited bizarre pleomorphic cell-forms. It was concluded that even environments toxified with extremely high oil concentrations and heavy-metals can be remediated rather effectively via their already existing native microorganisms. Image 1 • In wet sites, spilled oil occurs as tiny vesicles. • Bacteria live at borders between oil and the wet site thus getting nutrients from both. • Cells tolerate and degrade oil at concentrations of up to 41%. • They resist and detoxify heavy metals. • Cells respond to Cd2+ by exhibiting bizarre pleomorphism. [ABSTRACT FROM AUTHOR]

We investigated a microbe-based approach to be used for the biorecovery of valuable metals from e-waste. E-waste is a heterogeneous matrix at the microbial scale. Therefore, this study aims at taking advantage of bacterial-fungal (BF) interactions in order to mobilize and immobilize a selected metal present in e-waste. We used cadmium (Cd) and a selection of Cd-tolerant microorganisms from our culture collection or isolated from a naturally cadmium-contaminated soil. Several experiments were designed in order to use the synergistic bioremediation capabilities of BF couples to mobilize and immobilize Cd from a culture medium. Initial results showed that the selected synergistic BF couples are more tolerant to Cd concentrations than the organisms alone. However, setting the conditions leading to effective immobilization of this toxic metal still need further work. Using microbial consortia rather than single species represents an innovative alternative to traditional bioremediation approaches for the development of new biotechnological approaches in urban mining. [ABSTRACT FROM AUTHOR]