Multiple Heavy Metal Resistance Research Articles

Crucifer Lesion-Associated Xanthomonas Strains Show Multi-Resistance to Heavy Metals and Antibiotics.

Copper resistance in phytopathogens is a major challenge to crop production globally and is known to be driven by excessive use of copper-based pesticides. However, recent studies have shown co-selection of multiple heavy metal and antibiotic resistance genes in bacteria exposed to heavy metal and xenobiotics, which may impact the epidemiology of plant, animal, and human diseases. In this study, multi-resistance to heavy metals and antibiotics were evaluated in local Xanthomonas campestris pv. campestris (Xcc) and co-isolated Xanthomonas melonis (Xmel) strains from infected crucifer plants in Trinidad. Resistance to cobalt, cadmium, zinc, copper, and arsenic (V) was observed in both Xanthomonas species up to 25 mM. Heavy metal resistance (HMR) genes were found on a small plasmid-derived locus with ~ 90% similarity to a Stenotrophomonas spp. chromosomal locus and a X. perforans pLH3.1 plasmid. The co-occurrence of mobile elements in these regions implies their organization on a composite transposon-like structure. HMR genes in Xcc strains showed the lowest similarity to references, and the cus and ars operons appear to be unique among Xanthomonads. Overall, the similarity of HMR genes to Stenotrophomonas sp. chromosomal genomes suggest their origin in this genus or a related organism and subsequent spread through lateral gene transfer events. Further resistome characterization revealed the presence of small multidrug resistance (SMR), multidrug resistance (MDR) efflux pumps, and bla (Xcc) genes for broad biocide resistance in both species. Concurrently, resistance to antibiotics (streptomycin, kanamycin, tetracycline, chloramphenicol, and ampicillin) up to 1000 µg/mL was confirmed.

Mixed waste contamination selects for a mobile genetic element population enriched in multiple heavy metal resistance genes.

Mobile genetic elements (MGEs) like plasmids, viruses, and transposable elements can provide fitness benefits to their hosts for survival in the presence of environmental stressors. Heavy metal resistance genes (HMRGs) are frequently observed on MGEs, suggesting that MGEs may be an important driver of adaptive evolution in environments contaminated with heavy metals. Here, we report the meta-mobilome of the heavy metal-contaminated regions of the Oak Ridge Reservation subsurface. This meta-mobilome was compared with one derived from samples collected from unimpacted regions of the Oak Ridge Reservation subsurface. We assembled 1615 unique circularized DNA elements that we propose to be MGEs. The circular elements from the highly contaminated subsurface were enriched in HMRG clusters relative to those from the nearby unimpacted regions. Additionally, we found that these HMRGs were associated with Gamma and Betaproteobacteria hosts in the contaminated subsurface and potentially facilitate the persistence and dominance of these taxa in this region. Finally, the HMRGs were associated with conjugative elements, suggesting their potential for future lateral transfer. We demonstrate how our understanding of MGE ecology, evolution, and function can be enhanced through the genomic context provided by completed MGE assemblies.

The copper resistance mechanism in a newly isolated Pseudoxanthomonas spadix ZSY-33.

Resolving the heavy metal resistance mechanisms of microbes is crucial for understanding the bioremediation of the ecological environment. In this study, a multiple heavy metal resistance bacterium, Pseudoxanthomonas spadix ZSY-33 was isolated and characterized. The copper resistance mechanism was revealed by analysis of the physiological traits, copper distribution, and genomic and transcriptomic data of strain ZSY-33 cultured with different concentrations of copper. The growth inhibition assay in basic medium showed that the growth of strain ZSY-33 was inhibited in the presence of 0.5 mM copper. The production of extracellular polymeric substances increased at a lower concentration of copper and decreased at a higher concentration of copper. Integrative analysis of genomic and transcriptomic, the copper resistance mechanism in strain ZSY-33 was elucidated. At a lower concentration of copper, the Cus and Cop systems were responsible for the homeostasis of intracellular copper. As the concentration of copper increased, multiple metabolism pathways, including the metabolism of sulfur, amino acids, and pro-energy were cooperated with the Cus and Cop systems to deal with copper stress. These results indicated a flexible copper resistance mechanism in strain ZSY-33, which may acquire from the long-term interaction with the living environment.

Prevalence of Antibiotics and Cr, Cd, Cu Metals Co-resistant Coliforms in Refuse Dumpsites and Air of Surrounding Buildings in a Nigerian Urban Setting

Prevalence of co-resistance to antibiotics and Cr6+, Cd2+, and Cu2+ among coliforms from dumpsites and surrounding buildings’ indoor and outdoor air was investigated in Warri town, in the Niger Delta region of Nigeria. A total of 1,465 coliforms were isolated with McConkey and Eosin Methylene Blue Agar, and 38.8% had multiple antibiotics resistance (MAR) index ≥ 0.3 based on nine antibiotics. The prevalence of coliform bacteria with a MAR index of ≥ 0.3 varied (20.0 - 69.2%) and was lower in indoor and outdoor air farther away from the dumpsites. All dumpsite isolates were resistant to Cr and Cd but not to Cu, while resistance varied (48.5 - 100%) among indoor and outdoor air isolates. Plasmid-encoded resistance was indicated when the mean MAR (0.48 ± 0.04 - 0.5 ± 0.04) and multiple heavy metal resistance (MHMR) indexes (0.66 ± 0.00) declined to 0.11 ± 0.01 - 0.36 ± 0.03 and 0.33 ± 0.00, respectively, after curing. The differences in MAR indexes of isolates from the four dumpsite locations and between indoor and outdoor air isolates were only significant (P < 0.05) after curing, unlike the MHMR index, where there was no significant difference before and after curing. The prevalence of metals and antibiotics co-resistance, which was based on the concomitant reduction in MAR and MHMR indexes after curing, was higher in isolates from dumpsites than in indoor and outdoor air (32.1 - 38.1 vs 0.0 - 16.8%). The role of plasmid-encoded genes in the co-resistance phenomenon was therefore indicated. Dumpsites as selective pressure spots for the emergence of resistance genes in bacteria should be of public health concern in countries characterised by indiscriminate dumping of wastes, as this can result in potential spread to houses via bioaerosols.

Novel Plasmid Carrying Mobile Colistin Resistance Gene mcr-4.3 and Mercury Resistance Genes in Shewanella baltica: Insights into Mobilization of mcr-4.3 in Shewanella Species.

Shewanella species have been identified as progenitors of several clinically important antibiotic resistance genes. The aim of our study was to analyze Shewanella baltica strains isolated from the gut contents of wild Atlantic mackerel (Scomber scombrus) for the presence of both known and novel variants of antibiotic resistance genes (ARGs), using Illumina-based whole-genome sequencing (WGS). Thirty-three S. baltica strains were isolated from Atlantic mackerel collected in the northern North Sea. WGS revealed the presence of several new variants of class C and class D beta-lactamases. Nearly 42% (14/33) of the strains carried the mobile colistin resistance gene mcr-4.3. To understand the genetic context of mcr-4.3, we determined the complete genome sequence of strain 11FHM2, using a combination of Oxford Nanopore- and Illumina-based sequencing. The complete genome sequence is 5,406,724 bp long, with one contig representing a chromosome of 5,068,880 bp and three contigs representing novel plasmids (pSBP1, 194,145 bp; pSBP2_mcr4, 86,727 bp; and pSBP3, 56,972 bp). Plasmid pSBP2_mcr4 contains the mobile colistin resistance gene mcr-4.3, as well as the mercury resistance operon merRPAT. Plasmid pSBP1 carries genes encoding resistance against copper, zinc, chromium, and arsenic. Plasmid pSBP3 does not carry any antibiotic or heavy metal resistance genes. Analysis of the flanking region of mcr-4.3 suggests that a phage integrase may be involved in the mobilization of mcr-4.3 in Shewanella spp. Our results provide insights into the mobile mcr-4.3 present in Shewanella spp. and highlight the importance of the marine environment in the emergence and dissemination of clinically important resistance genes. IMPORTANCE We identified two new plasmids in Shewanella baltica isolated from wild Atlantic mackerel (Scomber scombrus) collected from the northern North Sea, one plasmid carrying the mcr-4.3 gene for colistin resistance and the operon merRPAT for mercury resistance and the other carrying multiple heavy metal resistance genes. The marine environment has been recognized as a source of new resistance genes that are found in human pathogens. Selection pressure from heavy metals is seen in the marine environment, especially associated with human activities, such as waste discharge, mining, and in aquaculture settings. This would help maintain and disseminate these plasmids in the environment. Our study provides insights into the mobilization of colistin resistance genes in Shewanella spp. and highlights the importance of the marine environment in the emergence and dissemination of clinically important antibiotic resistance genes.

Biofilm associated genotypes of multiple antibiotic resistant Pseudomonas aeruginosa

BackgroundPseudomonas aeruginosa is a ubiquitous environmental microorganism and also a common cause of infection. Its ability to survive in many different environments and persistently colonize humans is linked to its presence in biofilms formed on indwelling device surfaces. Biofilm promotes adhesion to, and survival on surfaces, protects from desiccation and the actions of antibiotics and disinfectants.ResultsWe examined the genetic basis for biofilm production on polystyrene at room (22 °C) and body temperature (37 °C) within 280 P. aeruginosa. 193 isolates (69 %) produced more biofilm at 22 °C than at 37 °C. Using GWAS and pan-GWAS, we found a number of accessory genes significantly associated with greater biofilm production at 22 °C. Many of these are present on a 165 kb region containing genes for heavy metal resistance (arsenic, copper, mercury and cadmium), transcriptional regulators and methytransferases. We also discovered multiple core genome SNPs in the A-type flagellin gene and Type II secretion system gene xpsD. Analysis of biofilm production of isolates of the MDR ST111 and ST235 lineages on stainless-steel revealed several accessory genes associated with enhanced biofilm production. These include a putative translocase with homology to a Helicobacter pylori type IV secretion system protein, a TA system II toxin gene and the alginate biosynthesis gene algA, several transcriptional regulators and methytransferases as well as core SNPs in genes involved in quorum sensing and protein translocation.ConclusionsUsing genetic association approaches we discovered a number of accessory genes and core-genome SNPs that were associated with enhanced early biofilm formation at 22 °C compared to 37 °C. These included a 165 kb genomic island containing multiple heavy metal resistance genes, transcriptional regulators and methyltransferases. We hypothesize that this genomic island may be associated with overall genotypes that are environmentally adapted to survive at lower temperatures. Further work to examine their importance in, for example gene-knockout studies, are required to confirm their relevance. GWAS and pan-GWAS approaches have great potential as a first step in examining the genetic basis of novel bacterial phenotypes.

Antibiotic and Heavy Metal Resistance of Escherichia coli Strains Isolated from the Seve Dam, and Konak Pond, Kilis, Turkey

Pollution of surface waters with coliform bacteria having antibiotic and heavy metal resistance has become an increasing public health risk. For this reason, antibiotic and heavy metal resistance profiles of fecal microorganisms in surface water samples collected from two different points (Seve Dam and Konak Pond, Kilis, Turkey) were analyzed in this study. The various physicochemical parameters such as pH, Temperature, Total Dissolved Solids (TDS), Electrical Conductivity (EC) of samples were also examined. The total coliform load in each sample was ˃1100 (MPN)/100 mL. As fecal indicator microorganisms, 21 Escherichia coli strains were isolated from sampling points. Despite the high coliform contamination, the multiple antibiotic resistance (MAR) index of E. coli was recorded as 0.187. The multiple heavy metal resistance (MHMR) index (0.202) was remarkably higher than the MAR value. Most isolates showed minimal inhibition concentrations (MIC) in the range of 25-1.600 μg/mL based on concentrations of heavy metals. These results indicate that surface waters may be discharge points of industrial and domestic wastewaters

Heavy-metal resistance mechanisms developed by bacteria from Lerma-Chapala basin.

Heavy-metal (HM) contamination is a huge environmental problem in many countries including Mexico. Currently, microorganisms with multiple heavy-metal resistance and/or plant-promoting characteristics have been widely used for bioremediation of HM-contaminated soils. The aim of the study was isolated bacteria with multiple heavy-metal resistance and to determinate the resistance mechanism developed by these organisms. A total of 138 aerobic bacteria were isolated from soil and sediments surrounding the Lerma-Chapala basin located in the boundary of the States of Michoacán and Jalisco states of Mexico. One hundred and eight strains showed at least 1 plant growth-promoting features. The Lerma-Chapala basin bacteria were also resistant to high concentrations of HMs including the metalloid arsenic. Sequence analysis of 16S RNA genes reveled that these bacteria were mainly affiliated to the phyla Proteobacteria (38%), Firmicutes (31%) and Actinobacteria (25%), covering 21 genera with Bacillus as the most abundant one. Among them, at least 27 putative novel species were detected in the genera Acinetobacter, Arthrobacter, Bacillus, Agrobacterium, Dyadobacter, Enterobacter, Exiguobacterium, Kluyvera, Micrococcus, Microbacterium and Psychrobacter. In addition, these bacteria developed various heavy-metal-resistance mechanisms, such as biosorption/bioaccumulation, immobilization and detoxification. Therefore, the bacteria isolated from soils and sediments of Lerma-Chapala basin could be used in bioremediation strategies.

Bioremediation of lead using bacterial isolates and study their plant relieving effect on wheat under metal contamination

Increasing concentration of heavy metals due to various anthropogenic activities is a serious problem. To overcome this issue, many chemical and physical methods are available but they are either directly or indirectly harmful to nature. By these methods more quality of chemicals are wasted. So, bioremediation is the best method to remove pollutants. It is an eco-friendly and cost-effective process. A low concentration of heavy metal is required to plant for their growth and metabolic process but at higher concentration, plants do not survive. With the use of microbes, we can survive plants at certain levels. During this work heavy metal tolerating microorganism was isolated and purified. Various tests were performed like staining, minimum inhibitory concentration, multiple heavy metal resistance, multiple antibiotic resistance, biochemical test, DNA isolation, in vitro examination of the wheat plant under the stress condition of lead (1000ppm).

Molecular genetic analysis of an XDR Pseudomonas aeruginosa ST664 clone carrying multiple conjugal plasmids

A group of ST664 XDR Pseudomonas aeruginosa strains have been isolated from a burn clinic. Here we decipher their resistomes and likely mechanisms of resistance acquisition. The complete nucleotide sequences of representative isolates were determined, by PacBio and Illumina MiSeq sequencing, and analysed for antimicrobial resistance (AMR) genes as well as sequence variations. S1-PFGE was used to determine the sizes and numbers of plasmids harboured by the isolates. Purified plasmid DNA was further sequenced by PacBio technology, closed manually and annotated by RAST. The mobility of plasmids was determined by conjugation assays. The XDR P. aeruginosa ST664 clone carries 11 AMR genes, including a blaKPC-2 gene that confers resistance to carbapenems. Most of the ST664 isolates carry three coexisting plasmids. blaKPC-2 and a cluster of three AMR genes (aadB-cmlA1-sul1) are encoded on a 475 kb megaplasmid pNK546a, which codes for an IncP-3-like replication and partitioning mechanism, but has lost the conjugative transfer system. Interestingly, however, pNK546a is mobilizable and can be transferred to P. aeruginosa PAO1 with the help of a co-residing IncP-7 conjugative plasmid. The blaKPC-2 gene is carried by an IS6100-ISKpn27-blaKPC-2-ΔISKpn6-Tn1403 mobile element, which might be brought into the ST664 clone by another co-resident IncP-1α plasmid, which is inclined to be lost. Moreover, pNK546a harbours multiple heavy metal (mercury, tellurite and silver) resistance modules. To the best of our knowledge, pNK546a is the first fully sequenced blaKPC-2-carrying megaplasmid from P. aeruginosa. These results give new insights into bacterial adaptation and evolution during nosocomial infections.

Microbial characterization of heavy metal resistant bacterial strains isolated from an electroplating wastewater treatment plant

Heavy metal pollution is one of the most widespread and complex environmental issues globally, posing a great threat to the ecosystem as well as human health. Bioremediation through heavy metal-resistant bacteria (HMRB) is currently the most promising technology to address this issue. To obtain HMRB to remediate heavy metal pollution potentially, 15 culturable HMRB strains were isolated from the sludge samples of an electroplating wastewater treatment plant (EWWTP), which belonged to the Bacillus, Shewanella, Lysinibacillus, and Acinetobacter genera. Their maximum tolerance concentrations to Cu2+, Ni2+, Mn2+, Co2+, and Cr2O72− were 40 mM, 10 mM, 200 mM, 40 mM, and 10 mM, respectively, and strain Mn1-4 showed much higher Mn2+ tolerance and removal effectiveness (3.355 g/L) than previously published reports. Moreover, multiple heavy metal-resistant genotypes and phenotypes were identified among these strains, of which strain Co1-1 carried the most of resistant gene sequences (10) and exhibited resistance to 7 categories of heavy metals, and the co-occurrence of heavy metal and antibiotic resistance were clearly observed in strain Ni1-3. In addition, flanked insert sequence (IS) elements on the heavy metal resistant genes (HMRGs) suggested that horizontal gene transfer (HGT) events may have resulted in multiple heavy metal resistance phenotypes and genotypes in these strains, and IS982 family transposase was presumed to result in the high Ni2+ tolerance in strain Ni1-3. This study expands our understanding of bacterial heavy metal resistance and provides promising candidates for heavy metal bioremediation.

Biosorption of heavy metals by a lead (Pb) resistant bacterium, Staphylococcus hominis strain AMB-2.

In the present study, a lead (Pb)-resistant bacterium, Staphylococcus hominis strain AMB-2 was isolated from Mandoli industrial area, Delhi and selected for heavy metal biosorption considering multiple heavy metal resistance. In the batch experiment, both living and dead biomasses of strain AMB-2 showed biosorption of Pb and cadmium (Cd) in single and binary systems as analyzed through Inductively coupled plasma-optical emission spectrometry. Living biomass exhibited more biosorption of metals than dead biomass in both single and binary systems. However, in the binary system, metals competed for the attachment sites on the bacterial surface, where Pb got more preference over Cd for the same. The underlying mechanism for the biosorption was attachment of the metal ions through functional groups onto the surface of the biomass as revealed by scanning electron microscope-energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction. Conclusively, this study displayed an effective biotreatment of Pb and Cd from aqueous medium using a low-cost biosorbent prepared from S. hominis strain AMB-2 considering biosafety of microorganisms and an eco-friendly approach.

Draft Genome Sequence of Heavy Metal-Resistant Bacillus cereus NWUAB01

Bacillus cereus NWUAB01 was isolated from a gold-mining site in Vryburg, South Africa, for its multiple heavy metal resistance properties. Here, we report the draft genome sequence of B. cereus NWUAB01 obtained with Illumina sequencing.

Multidrug-Resistant Salmonella enterica Isolated from Food Animal and Foodstuff May Also Be Less Susceptible to Heavy Metals.

Salmonella enterica is a foodborne pathogen showing increasing multidrug resistance (MDR). We characterized the antimicrobial resistance (AMR) genotype using microarrays in a panel of 105 nontyphoidal S. enterica isolated from food animals and foodstuff. Nineteen isolates were chosen on the basis of their MDR and virulence for determination of heavy metal susceptibilities and screened by polymerase chain reaction for heavy metal resistance genes. Whole-genome sequencing (WGS) was performed on three isolates carrying clinically important AMR genes and the cdtB toxin gene to detect other heavy metal resistance mechanisms, and conjugation assays were performed to evaluate transfer of AMR/toxin genes with heavy metal resistance genes. AMR genotyping results showed isolates harbored between 1 and 12 mobile AMR genes, with 58% being classified as MDR. The tested subset of isolates showed reduced susceptibility to zinc (78%), copper (68%), silver (63%), arsenic (47%), and tellurite (26%); phenotypes that could be attributed to zitB (n = 32%), pcoA/pcoD (n = 32%), tcrB (n = 16%), arsB (n = 16%), silA/silE (n = 42%), and terF (n = 26%) genes. WGS confirmed the presence of other heavy metal resistance genes such as copA, cusA, and czcD. Isolates often harbored multiple heavy metal resistance genes. Two strains (Sal25 and Sal368) were able to conjugate with Escherichia coli J53 at a relatively high frequency (∼10-4 colony-forming units per recipient). Transformants selected in the presence of copper harbored either an IncHI2 (J53/Sal25 transconjugant) or IncF (J53/Sal368 transconjugant) plasmid with decreased susceptibilities to tellurite, zinc, copper, cobalt, arsenic, lead, mercury, and silver. blaCTX-M-1 and mcr-1 genes were also transferred to one transconjugant, and tet(M) and blaTEM-1 genes to the other. This work shows the presence of a diversity of AMR genes in this zoonotic pathogen, and suggests that heavy metals may contribute to selection of clinically important ones through the food chain, such as the plasmid-mediated colistin resistance gene mcr-1.

Nickel and cobalt resistance properties of Sinorhizobium meliloti isolated from Medicago lupulina growing in gold mine tailing.

Sinorhizobium meliloti CCNWSX0020, isolated from root nodules of Medicago lupulina growing in gold mine tailings in the northwest of China, displayed multiple heavy metal resistance and growth promotion of M. lupulina. In our previous work, the expression level of dmeR and dmeF genes were induced by Cu2+ through comparative transcriptome approach. Based on protein analysis, the dmeF encoded for a protein which showed a 37% similarity to the cation transporter DmeF of Cupriavidus metallidurans, whereas dmeR encoded transcriptional regulator which was highly homologous with DmeR belonging to RcnR/CsoR family metal-responsive transcriptional regulator. In addition to copper, quantitative real-time PCR analysis showed that dmeR and dmeF were also induced by nickel and cobalt. To investigate the functions of dmeR and dmeF in S. meliloti CCNWSX0020, the dmeR and dmeF deletion mutants were constructed. The dmeF mutant was more sensitive to Co2 + and Ni2 + than the wild type strain. Pot experiments were carried out to determine whether the growth of M. lupulina was affected when the dmeF gene was knocked out in the presence of nickel or cobalt. Results indicated that the nodule number of the host plant inoculated with the dmeF deletion mutant was significantly less than the S. meliloti CCNWSX0020 wild-type in the presence of Co2 + or Ni2 +. However, when standardized by nodule fresh weight, the nitrogenase activities of nodules infected by the dmeF deletion mutant was similar to nitrogenase activity of the wild type nodule.

Multiple Heavy Metal and Antibiotic Resistance of Acinetobacter baumannii Strain HAF – 13 Isolated from Industrial Effluents

The emergence of multiple metal/antibiotic resistance among bacterial populations poses a potential threat to human health. Heavy metal and antibiotic resistance have been shown to have a strong correlation in nature, and their inter-relation is an important subject of study. The present study had an objective to isolate and identify multiple metal/antibiotic resistant bacteria from industrial wastewater of a Plastic Factory at Hafar Al Baten governorate, Saudi Arabia. Initially a total of 14 bacterial cultures (coded HAF – 1 to HAF – 14) were isolated on nutrient agar plates supplemented with different concentrations; 10, 15, 25, 25 and 30 mg/l of the five heavy metals; Hg2+, Pb2+, Cd2+, As5+ and Cr6+ respectively. Out of 14 isolates, 5 (35.71 %) isolates (HAF – 2, HAF – 6, HAF – 7, HAF – 9 & HAF – 13) were selected as a multiple heavy metal resistant (MHMR) organisms with maximum tolerable concentrations (MTCs); 75 – 100 mg/l for Hg2+, 125 – 175 mg/l for Pb2+, 200 mg/l for Cd2+ and 200 – 250 mg/l for Cr6+ and As5+. Antibiotic resistance pattern of the selected MHMR isolates was determined by Kirby-Bauer disc diffusion method against 15 different antibiotics belonging to 10 classes. Out of 5 isolates, 4 (80 %) isolates were multiple antibiotic resistance (MAR) with varying degrees. Among them isolate, HAF – 13 showed a wide range of resistance to all tested antibiotics; Amikacin, Augmentin, Ceftazidime, Chloramphenicol, Ciprofloxacin, Clindamycin, Cotrimoxazole, Erythromycin, Gentamicin, Levofloxacin, Oxacillin, Tetracycline, Vancomycin and Penicillin Gexcept Imipenem. Strain HAF – 13 was selected for its multiple metal/antibiotic resistance and identified by morphological, physiological and biochemical characteristics in addition to the phylogenetic analysis of the nucleotide sequence of 16S rRNA gene, which indicated that this strain is belonged to the genus Acinetobacter with high similarity 98% to Acinetobacter baumannii (accession number KU310899.1) and designated Acinetobacter baumannii strain HAF – 13.

Comparative Study of Co-Resistance Pattern of Bacteria Isolated from Waste Water of Hospital Discharge and Soil of Industrial Area

The rise of heavy metal pollution and antibiotic resistant bacteria in soil and water is a key challenge to worldwide public health. The aim of current study is assessment of microbial load and co-resistance (cadmium and antibiotics) of bacteria isolated from the water of hospital waste discharge and soil of industrial of Lucknow and Allahabad (U.P. India). Soil samples were collected from different location of Uttar Pradesh. The samples were analyzed for presence of microbial load by heterotrophic plate count (HPC) ranged from 160cfu/ml-400x10⁵cfu/ml. Isolated bacteria assessed for multiple antibiotics and heavy metal resistance. The study was carried out on the basis of maximum threshold limit for the cadmium by the isolates. MIC test of isolates was performed for detection of tolerance against cadmium metal. From 34 potent isolates only ten isolates (AIA2, AIA4, BBAU2, BBAU4, SIA2, BSS1, BSS2, BSS4, HWS2, and HWS1) were able to grow at high cadmium level. While, out of ten only two isolates BSS2 and BSS4 found to grow at maximum threshold limit at 1100ppm. In antibiotic resistance test all the isolates had resistant property against cpm and most of the heavy metal resistant isolates had high multiple antibiotic resistant (MAR) index value. High MAR values were seen in BSS2 and AIA4 isolates.

Isolation and Characterization of Arsenic Resistant Pseudomonas Stutzeri ASP3 for its Potential in Arsenic Resistance and Removal

Inorganic arsenic both arsenite As (III) and arsenate As (V) constitute the highest toxicological risk associated with arsenic in drinking water. Novel methods are in demand for its removal from water, especially in rural areas. For this purpose, the potential of different microbes in arsenic resistance and removal from water has gained interests worldwide. This study investigates the arsenic resistance and removal capacity of a bacterial strain isolated from arsenic enriched water of Rautahat district in Nepal. The concentration of arsenic was by hydride generation atomic absorption spectrophotometer. The isolated bacterium showed high resistance to sodium arsenate up to 4,680.15 mg/l and sodium arsenite up to 649.55 mg/l. The bacterium also conferred multiple heavy metal resistance to zinc chloride (136.28 mg/l), copper sulphate (249.68 mg/l), mercuric chloride (5.43 mg/l) and silver nitrate (3.39 mg/l). The growth rate calculated in the presence of 129.01 mg/l of sodium arsenite was 0.35 h-1 with doubling time of 1.96 h. The strain showed growth in the range of 25–45 °C (optimum 30-35 °C), pH 6 – 9 (optimum 7.5-8.5) and tolerated up to 10% of NaCl. The PCR-based 16S rDNA sequence analysis revealed that the isolated As resistant bacterium is a close relative to P. stutzeri (99%) with 30 hits. The bacterium removed 82.97 % of As (V) and 49.4% of As (III) from culture medium amended with 200 mg/l sodium arsenate and 74.92 mg/l of sodium arsenite respectively.

Genome of Cupriavidus sp. HMR-1, a Heavy Metal-Resistant Bacterium

Cupriavidus sp. HMR-1 was isolated from a heavy metal-enriched culture of activated sludge from a wastewater treatment plant in Hong Kong. Here, we release the HMR-1 genome to provide basic genetic characteristics for a better understanding of its multiple heavy metal resistance properties.

Characterization of ACC deaminase-producing endophytic bacteria isolated from copper-tolerant plants and their potential in promoting the growth and copper accumulation of Brassica napus

One hundred Cu-resistant-endophytic bacteria were isolated from Cu-tolerant plants grown on Cu mine wasteland, of which, eight Cu-resistant and 1-aminocyclopropane-1-carboxylate (ACC) deaminase-producing endophytic bacteria were obtained based on the ACC deaminase activity of the bacteria and characterized with respect to metal resistance, production of ACC deaminase, indole-3-acetic acid (IAA) as well as siderophores and mineral phosphate solubilization. Ralstonia sp. J1-22-2, Pantoea agglomerans Jp3-3, and Pseudomonas thivervalensis Y1-3-9 with higher ACC deaminase activity (ranging from 213 to 370 μM α-ketobutyrate mg −1 h −1) were evaluated for promoting plant growth and Cu uptake of rape grown in quartz sand containing 0, 2.5, and 5 mg kg −1 of Cu in pot experiments. The eight bacteria were found to exhibit different multiple heavy metal resistance characteristics, to show different levels of ACC deaminase activity and to produce indole acetic acid. Seven bacteria produced siderophores and solubilized inorganic phosphate. Pot experiments showed that inoculation with the strains (J1-22-2, Jp3-3, and Y1-3-9) was found to increase the biomass of rape. Increases in above-ground tissue Cu contents of rape cultivated in 2.5 and 5 mg kg −1 of Cu-contaminated substrates varied from 9% to 31% and from 3 to 4-fold respectively in inoculated-rape plants compared to the uninoculated control. The maximum Cu uptake of rape was observed after inoculation with P. agglomerans Jp3-3. The results show that metal-resistant and plant growth promoting endophytic bacteria play an important role in plant growth and Cu uptake which may provide a new endophytic bacterial-assisted phytoremediation of Cu-contaminated environment.