Effect of bacterial inoculation of strains of pseudomonas aeruginosa,alcaligenes feacalis and bacillus subtilis on germination,growth and heavy metal (cd,cr, and ni) uptake of brassica juncea

Bacterial inoculation may influence Brassica juncea growth and heavy metal (Ni, Cr, and Cd) accumulation. Three metal tolerant bacterial isolates (BCr3, BCd33, and BNi11) recovered from mine tailings, identified as Pseudomonas aeruginosa KP717554, Alcaligenes feacalis KP717561, and Bacillus subtilis KP717559 were used. The isolates exhibited multiple plant growth beneficial characteristics including the production of indole-3-acetic acid, hydrogen cyanide, ammonia, insoluble phosphate solubilization together with the potential to protect plants against fungal pathogens. Bacterial inoculation improved seeds germination of B. juncea plant in the presence of 0.1 mM Cr, Cd, and Ni, as compared to the control treatment. Compared with control treatment, soil inoculation with bacterial isolates significantly increased the amount of soluble heavy metals in soil by 51% (Cr), 50% (Cd), and 44% (Ni) respectively. Pot experiment of B. juncea grown in soil spiked with 100 mg kg^?1 of NiCl₂, 100 mg kg^?1 of CdCl₂, and 150 mg kg^?1 of K₂Cr₂O₇, revealed that inoculation with metal tolerant bacteria not only protected plants against the toxic effects of heavy metals, but also increased growth and metal accumulation of plants significantly. These findings suggest that such metal tolerant, plant growth promoting bacteria are valuable tools which could be used to develop bio-inoculants for enhancing the efficiency of phytoextraction.     

Bioremediation of Heavy Metals in Liquid Media Through Fungi Isolated from Contaminated Sources

Wastewater particularly from electroplating, paint, leather, metal and tanning industries contain enormous amount of heavy metals. Microorganisms including fungi have been reported to exclude heavy metals from wastewater through bioaccumulation and biosorption at low cost and in eco-friendly way. An attempt was, therefore, made to isolate fungi from sites contaminated with heavy metals for higher tolerance and removal of heavy metals from wastewater. Seventy-six fungal isolates tolerant to heavy metals like Pb, Cd, Cr and Ni were isolated from sewage, sludge and industrial effluents containing heavy metals. Four fungi (Phanerochaete chrysosporium, Aspegillus awamori, Aspergillus flavus, Trichoderma viride) also were included in this study. The majority of the fungal isolates were able to tolerate up to 400 ppm concentration of Pb, Cd, Cr and Ni. The most heavy metal tolerant fungi were studied for removal of heavy metals from liquid media at 50 ppm concentration. Results indicated removal of substantial amount of heavy metals by some of the fungi. With respect to Pb, Cd, Cr and Ni, maximum uptake of 59.67, 16.25, 0.55, and 0.55 mg/g was observed by fungi Pb3 (Aspergillus terreus), Trichoderma viride, Cr8 (Trichoderma longibrachiatum), and isolate Ni27 (A. niger) respectively. This indicated the potential of these fungi as biosorbent for removal of heavy metals from wastewater and industrial effluents containing higher concentration of heavy metals.     

Impact of industrial waste water effluents on mycoflora of the shore sediments of the 3rd oxidation pond,with reference to biosorption of heavy metals

The third oxidation pond at 10th of Ramadan desert receives a number of industrial waste water effluents contaminated with the heavy metal ions Zn, Cd, Cu and Ni. The species diversity and fungal community structure of seven different sites at the onshore sediments and offshore were studied. Mycological analysis resulted in isolation of 3912 fungal colonies, 11.7% of this count were recovered from the onshore sediment sites (4 sites) whereas 88.3% were from the offshore sites (3 sites), in the desert. Fungal counts and species diversity at the onshore sites tend to increase with increasing distance far from the waste water input. A complete accordance was observed among the total fungal counts and species variabilities with organic matter content at each sampling site. This relationship was reversed in case of heavy metal contents with both counts and diversity. Seventeen fungal species belonging to seven genera were isolated from all sites under study. Aspergillus spp. constituted the majority of the isolates (51.7% of the total isolates), followed by Curvularia, Cephalosporium, and Humicola. Of nine isolated Aspergillus spp., A. humicola was the most dominant (37.4% of the total catch) and appeared at all polluted sites. Therefore, A. humicola was chosen to investigate its potential for heavy metals sorption from the contaminated waste water effluent. Four days old biomass pellets could sorb a large amount of heavy metals according to the following sequence: Zn>Cd>Cu>Ni ions. Agitation significantly increased Zn and Cd sorption, but not Cu and Ni. Heavy metals sorption took place at a wide pH range and particularly increased at alkaline pH (8-9).     

Adsorption of Heavy Metals by Paenibacillus validus Strain MP5 Isolated from Industrial Effluent–Polluted Soil

The present investigation was carried out to isolate bacterial strains from soil/mud samples of metal-polluted environment to check whether the natural adaptation of microbes has equipped them for bioremediation of toxic heavy metals. The primary and secondary screening resulted in 50 mesophilic autotrophic isolates of microbial consortium adapted for metal tolerance and bioadsorption potentiality. The multimetal tolerance in bacterial strain was developed by sequential transfer to higher concentrations of Cd, Cr, Cu, Pb, Ni, and Zn. The isolates were checked for their biosolubilization potential with copper-containing metal sulfide ores, viz. chalcopyrite exhibited 64% and covellite 54% solubilization in the presence of 10^?3 M multiple heavy metals on the fifth day at 35°C and pH 6.0. Metal adsorption of highly potential isolate, i.e., Paenibacillus validus MP5, studied by inductively coupled plasma optical emission spectroscopy (ICP-OES), showed maximum adsorption of Zn 27%, followed by Ni and Cd 16%, Cr 15%, Co 9%, and Pb 7.5% in chalcopyrite, which suggested its possible role in decontamination of metal-polluted sites.     

Detecting the heavy metal tolerance level in ectomycorrhizal fungi <Emphasis Type="Italic">in vitro</Emphasis>

Summary Eight isolates of ectomycorrhizal fungi namely, Laccaria fraterna (EM-1083),Laccaria laccata (EM-1191), Pisolithus tinctorius (EM-1081),Pisolithus tinctorius (EM-1293), Scleroderma cepa (EM-1233),Scleroderma flavidum (EM-1235),Scleroderma verucosum, (EM-1283) and Hysterangium incarceratum (EM-1185) were grown on specially designed cocktail media prepared by adding various concentrations of different heavy metals namely Al, As, Cd, Cr, Ni and Pb. The heavy metals were selected keeping in view their relative abundance in coal ash and potential toxicity. The fungal isolates were grown on such designed cocktail media. The colony diameter was used for the measurement of the fungal growth. Total heavy metal accumulated in the mycelia was assayed by atomic absorption spectrophotometry.In relation to metal tolerance ability in general,Hysterangium incarceratum (EM-1185) showed maximum tolerance with respect to growth, Laccaria fraterna (EM-1083) and Pisolithus tinctorius (EM-1293) also showed considerable tolerance to the heavy metals tested. In relation to metal uptake in particular, Pisolithus tinctorius (EM-1293), has reported maximum uptake of Al (34642.58 ppm), Cd (302.12 ppm) and Pb (3501.96 ppm). In Laccaria fraterna (EM-1083), As (130.57 ppm) and Cr (402.38 ppm) uptake was recorded maximum; and Hysterangium incarceratum (EM-1185) has recorded maximum Ni (2648.59 ppm) uptake among the three suitable isolates documented here.     

X-ray Fluorescence (XRF) Analysis of Soil Heavy Metal Pollution from an Industrial Area in Kumasi,Ghana

Knowledge of soil heavy metal concentration is very important for assessing the purity and quality of the soil in an environment. The concentrations of nine heavy metals (NHM), Zn, Pb, Cr, Cu, Co, Ni, Cd, Hg, and As, from the near-surface soils (～ 0–15 cm) from an industrial cluster in Kumasi, Ghana, were qualitatively and quantitatively measured and analyzed using X-ray fluorescence (XRF) spectroscopy analysis. The sources of these NHM were mainly anthropogenic as a result of the indiscriminate industrial waste disposal. In all, a total of about 100 soil samples were taken from six sampling sites, four of which were industrial and the remaining two residential. Forty soil samples out of the total number were carefully selected for elemental analyses and the mean heavy metal concentrations were calculated using statistical methods. The results from locations of high industrial impact showed that the mean concentrations of the NHM present in the soil were in the order of Zn (189.2?908.6 mgkg^?1), Pb (133.7?571.3 mgkg^?1), Cr (91.3?545.8 mgkg^?1), Cu (62.9?334.6 mgkg^?1), Co (38.6?81.9 mgkg^?1), Ni (12.4?30.9 mgkg^?1), Cd (6.9?13.2 mgkg^?1), Hg (5.5?10.4 mg kg^?1), and As (2.3?18.6 mgkg^?1). Apart from Ni and As, all the heavy metals recorded concentrations that ranged from 10?900% higher than their respective threshold limit values (TLVs). Heavy metal concentrations from the residential sites were comparatively far lower with only Cr, Cd, and Hg registering concentrations between 65?250% above their TLVs. The cluster with its residential communities is at a serious risk of soil heavy metal toxicity and awareness to this needs to be created as such.     

Identification and characterization of Cr-, Cd-, and Ni-tolerant bacteria isolated from mine tailings

Eleven bacterial strains were isolated from soil samples collected from mine tailings. Bacterial strains were checked for tolerance against heavy metals (Cr, Cd, Ni), using the agar dilution method. All the strains showed multiple tolerances against heavy metals, but the most promising results appeared in strains BCr3, BCd33, and BNi11: they were tolerant to 15 mM of Cr⁶⁺, 7.5 mM of Cd²⁺, and 10 mM of Ni²⁺, respectively. The effect of heavy metals on bacterial growth was tested together with their ability to grow in different pH, NaCl, and temperature values. Bacterial isolates grew well between pH 7.5 and 8.5. The optimum temperature for maximum growth was between 35 and 37°C, and no significant change in bacterial growth was observed in the presence of 2% NaCl. In addition, the bioaccumulation potential of bacterial strains was investigated. Bacterial strains BCr3, BCd33, and BNi11 showed high bioaccumulation ability of Cr (68.7%), Cd (72.4%), and Ni (69.8%), respectively. All bacterial isolates were identified by 16S rRNA gene sequencing. Analysis of plasmid content revealed that all bacterial isolates contained a single plasmid. Further, polymerase chain reaction together with DNA sequence analysis was used to screen all bacterial strains for the presence metal tolerance genes (czcD, chrA, chrB, czcB, czcC, nccA, and cadA) on both plasmid and chromosomal genomes.     

Heavy metal tolerance in marine strains of Yarrowia lipolytica

Heavy metal tolerance of two marine strains of Yarrowia lipolytica was tested on solid yeast extract peptone dextrose agar plates. Based on minimum inhibitory concentration esteems, it is inferred that the two strains of Y. lipolytica were tolerant to heavy metals such as Pb(II), Cr(III), Zn(II), Cu(II), As(V), and Ni(II) ions. The impact of various heavy metal concentrations on the growth kinetics of Y. lipolytica was likewise assessed. With increased heavy metal concentration, the specific growth rate was reduced with delayed doubling time. Furthermore, biofilm development of both yeasts on the glass surfaces and in microtitre plates was assessed in presence of different heavy metals. In microtitre plates, a short lag phase of biofilm formation was noticed without the addition of heavy metals in yeast nitrogen base liquid media. A lag phase was extended over increasing metal concentrations of media. Heavy metals like Cr(VI), Cd(II), and As(V) are contrastingly influenced on biofilms’ formation of microtitre plates. Other heavy metals did not much influence on biofilms development. Thus, biofilm formation is a strategy of Y. lipolytica under stress of heavy metals has significance in bioremediation process for recovery of heavy metals from contaminated environment.

     

Activation and ecological risk assessment of heavy metals in dumping sites of Dabaoshan mine,Guangdong province,China

In Dabaoshan mine, dumping sites were the largest pollution source to the local environment. This study analyzed the activation and ecological risk of heavy metals in waste materials from five dumping sites. Results indicated that the acidification of waste materials was severe at all dumping sites, and pH decreased below 3.0 at four of the five sites. There was a drastic variation in Cu, Zn, Pb, and Cd concentrations in different sites. Site A with 12915.3 mg kg^?1 Pb and 7.2 mg kg^?1 Cd and site C with 1936.2 mg kg^?1 Cu and 5069.0 mg kg^?1 Zn were severely polluted. Higher concentrations of water-soluble Cu were probably the critical constraint for local pioneer plants. A significant positive correlation was found between the concentrations of water-soluble and HOAc-extractable elements, and the regression analysis showed that, compared with Cu, Zn and Cd, Pb was more difficult to be transformed from HOAc extractable to water soluble. Concentration of water soluble metals should be an important index, same as concentration of HOAc extractable metals, in assessing ecological risks, availability, and toxicity of heavy metals. The modified ecological risk index indicated that all dumping sites had very high potential ecological risks. It is necessary to decrease the availability of heavy metals to reduce the impact of waste materials on environment.     

Quantification of Heavy Metals in Mining Affected Soil and Their Bioaccumulation in Native Plant Species

Several anthropogenic and natural sources are considered as the primary sources of toxic metals in the environment. The current study investigates the level of heavy metals contamination in the flora associated with serpentine soil along the Mafic and Ultramafic rocks northern-Pakistan. Soil and wild native plant species were collected from chromites mining affected areas and analyzed for heavy metals (Cr, Ni, Fe, Mn, Co, Cu and Zn) using atomic absorption spectrometer (AAS-PEA-700). The heavy metal concentrations were significantly (p < 0.01) higher in mine affected soil as compared to reference soil, however Cr and Ni exceeded maximum allowable limit (250 and 60 mg kg^?1, respectively) set by SEPA for soil. Inter-metal correlations between soil, roots and shoots showed that the sources of contamination of heavy metals were mainly associated with chromites mining. All the plant species accumulated significantly higher concentrations of heavy metals as compared to reference plant. The open dumping of mine wastes can create serious problems (food crops and drinking water contamination with heavy metals) for local community of the study area. The native wild plant species (Nepeta cataria, Impatiens bicolor royle, Tegetis minuta) growing on mining affected sites may be used for soil reclamation contaminated with heavy metals.     

High levels of multiple metal resistance and its correlation to antibiotic resistance in environmental isolates of Acinetobacter

Forty strains of Acinetobacter were isolated from different environmental sources. All the strains were classified into four genospecies, i.e. A. baumannii (33 isolates), A. calcoaceticus (three isolates), A. junii (three isolates) and A. genospecies3 (one isolate). Susceptibility of these 40 strains to salts of 20 heavy metals and 18 antibiotics was tested by the agar dilution method. All environmental isolates of Acinetobacter were resistant to multiple metal ions (minimum 13 metal ions) while all but one of the strains were resistant to multiple antibiotics (minimum four antibiotics). The maximum number of strains were found to be sensitive to mercury (60% strains) while all strains were resistant to copper, lead, boron and tungsten even at 10 mm concentration. Salts of these four metal ions may be added to the growth medium to facilitate selective isolation of Acinetobacter. Rifampicin and nalidixic acid were the most toxic antibiotics, inhibiting 94.5 and 89.5% of the acinetobacters, respectively. A. genospecies3 was found to be the most resistant species, tolerating high concentrations of all the 20 metal ions and also to a greater number of antibiotics than any other species of Acinetobacter tested. An inhibitory concentration (10 mm) of Ni²⁺ and Zn²⁺ was observed to inhibit the growth of all of the clinical isolates but allowed the growth of the environmental isolates, facilitating the differentiation between pathogenic and non-pathogenic acinetobacters.     

Impact of Heavy Metals on the Selective Phenotypical Markers of Pseudomonas aeruginosa

The aim of this study was to characterize the impact of heavy metals on phenotypical markers of Pseudomonas aeruginosa. Twenty-two isolates of P. aeruginosa, either clinical (20) or secondary treated wasterwater (2), were used to inoculate micro-ecosystems of sterile distilled water or secondary waste effluent in the presence of subminimal inhibitory concentrations of a variety of heavy metals commonly encountered in the aquatic naturally habitat (Ca²⁺, Co²⁺, Cr³⁺, Cu²⁺, Hg²⁺, Ni²⁺, Zn²⁺). Micro-ecosystems were exposed to visible light at laboratory temperature and individual strains were reisolated after a 1-, 3-, or 6-month period. The re-isolates (129) were characterized using hierarchical classification analysis in order to define affinities among variants of P. aeruginosa. Subsequently, discriminant analysis was used to detect eventual relationships among the different phenotypical markers studied. Results of the hierarchical classification, based on qualitative or quantitative approaches, showed clearly that incubation of P. aeruginosa in the presence of heavy metals altered the studied phenotypical markers, namely serotype, phage type, MIC of metals, and pyocin type. Discriminant analysis showed that the studied phenotypical markers could be classified into four clusters: C1 (L1 and L2 phage types, Hg tolerance and/or resistance, S2 serotype), C2 (P2 pyocin type, Cd tolerance and/or resistance, S1 serotype), C3 (Co and Cr tolerance and/or resistance) and C4 (P1 pyocin type, Ni, Zn, and Cu tolerance and/or resistance).     

Isolation and Molecular Characterization of Heavy Metal-Resistant Alcaligenes faecalis from Sewage Wastewater and Synthesis of Silver Nanoparticles

Environmental pollution with toxic heavy metals is increasing throughout the world alongside industrial development. Microorganisms and microbial products can be highly efficient bioaccumulators of soluble and particulate forms of metals, especially dilute external solutions. Microbe related technologies (Biotechnology) may provide an alternative or additive conventional method for metal removal or metal recovery. This study dealt with isolation, identification and characterization of heavy metal-resistant (Pb²⁺, Cd²⁺, Al³⁺, Cu²⁺, Ag²⁺ and Sn²⁺) bacteria from sewage wastewater at Taif Province, Saudi Arabia. Nine bacterial isolates were selected by using an enrichment isolation procedure based on high level of heavy metal resistance. All the isolates showed high resistance to heavy metals with Minimum Inhibitor Concentration (MIC) ranging from 800 μg/ml to 1400 μg/ml. All nine resistant isolates showed multiple tolerances to heavy metals. On the basis of morphological, biochemical and 16S rRNA characterization, the most potent isolates (Cd1-1, Ag1-1, Ag1-3 and Sn1-1) were identified as Alcaligenes faecalis. Scanning electron microscope analysis showed that the morphology of Alcaligenes faecalis Ag1-1 was unchanged after growth in medium without and with addition of Ag²⁺ indicative Ag²⁺ is not toxic to the isolate under the conditions tested. The ability of Alcaligenes faecalis Ag1-1 to synthesize sliver nanoparticles was examined. The heavy metal-resistant bacteria obtained could be useful for the bioremediation of heavy metal-contaminated environment.     

Biosorption of Heavy Metals from Wastewater by Biosolids

In a study where the removal of heavy metals from wastewater is the primary aim, the biosorption of heavy metals onto biosolids prepared as Pseudomonas aeruginosa immobilized onto granular activated carbon was investigated in batch and column systems. In the batch system, adsorption equilibriums of heavy metals were reached between 20 and 50 min, and the optimal dosage of biosolids was 0.3 g/L. The biosorption efficiencies were 84, 80, 79, 59 and 42 % for Cr(VI), Ni(II), Cu(II), Zn(II) and Cd(II) ions, respectively. The rate constants of biosorption and pore diffusion of heavy metals were 0.013–0.089 min^–1 and 0.026–0.690 min^–0.5. In the column systems, the biosorption efficiencies for all heavy metals increased up to 81–100 %. The affinity of biosorption for various metal ions towards biosolids was decreased in the order: Cr = Ni > Cu > Zn > Cd.     

Soil quality around a solid waste dumpsite in Port Harcourt, Nigeria

The levels of soil parameters and selected heavy metals around a solid waste dumpsite receiving untreated wastes from all sources and a control site within Port Harcourt, Nigeria have been examined. Top soil (0–15 cm) and sediment samples were collected and analysed for pH value, particle size, total nitrogen, potassium, available phosphorus, organic matter, effective cation exchange capacity, cadmium, nickel and lead using standard methods. The results showed that the waste dump contributed to the high levels of nutrients and heavy metals. The dry season mean concentrations were: organic matter (5.28 ± 1.34% or 132,422.4 kg ha^?1), K (1.60 ± 0.52 meq per 100 g), N (0.09 ± 0.06% or 2257.2 kg ha^?1), Av.P (15.11 ± 7.57 μg g^?1), Cd (1.34 ± 0.72 μg g^?1), Ni (4.10 ± 1.63 μg g^?1) and Pb (38.85 ± 22.18 μg g^?1) while the wet season mean concentrations were organic matter (5.46 ± 1.39% or 136,936.8 kg ha^?1), K (2.79 ± 0.81 meq per 100 g), N (0.10 ± 0.05% or 2508 kg ha^?1), Av.P (9.22 ± 2.69 μg g^?1), Cd (1.72 ± 1.22 μg g^?1), Ni (14.95 ± 14.94 μg g^?1) and Pb (53.50 ± 40.09 μg g^?1). There was efficient mineralization process in the area. The texture of soil on the main dumpsite was loamy sand, which suggests that the ground water in the area is susceptible to contamination by surface pollutants. The texture of soil at the control site is sandy loam while sediment has the textural class of sand. Decomposed organic materials and agricultural activities influenced the texture of soils. The soils from the main dump and sediment were slightly alkaline while the control soil was moderately acidic. In both seasons, a significant variation exists (P < 0.05) between the metal concentrations in soil at the main dump and those in the sediments with a positive correlation (r = 0.572149) in the wet season and (r = 0.956647) in the dry season. The presence of liming materials and activities of microorganisms on the waste dump increased the pH of the soils. The accumulation of nutrients results in the luxuriant growth of plants/crops on the waste dump.     

Lead,cadmium and nickel removal efficiency of white-rot fungus Phlebia brevispora

Widespread of heavy metals contamination has led to several environmental problems. Some biological methods to remove heavy metals from contaminated wastewater are being widely explored. In the present study, the efficiency of a white-rot fungus, Phlebia brevispora to remove different metals (Pb, Cd and Ni) has been evaluated. Atomic absorption spectroscopy of treated and untreated metal containing water revealed that all the metals were efficiently removed by the fungus. Among all the used metals, cadmium was the most toxic metal for fungal growth. Phlebia brevispora removed maximum Pb (97·5%) from 100 mmol l⁻¹ Pb solution, which was closely followed by Cd (91·6%) and Ni (72·7%). Scanning electron microscopic images revealed that the presence of metal altered the morphology and fine texture of fungal hyphae. However, the attachment of metal on mycelia surface was not observed during energy-dispersive X-ray analysis, which points towards the intracellular compartmentation of metals in vacuoles. Thus, the study demonstrated an application of P. brevispora for efficient removal of Pb, Cd and Ni from the metal contaminated water, which can further be applied for bioremediation of heavy metals present in the industrial effluent.     

Isolation of clinically relevant fungal species from solid waste and environment of dental health services

Aims: This study was undertaken to detect, identify and determine antifungal susceptibility of yeast strains isolated from dental solid waste and to evaluate airborne fungi in the Brazilian dental health care environment and in the waste storage room. Methods and Results: A group of 17 yeast strains were identified by macroscopic and microscopic characteristics, API 20C Aux system and Multiplex PCR. All 104 airborne fungal colonies were identified by macroscopic and microscopic morphology. The CLSI broth microdilution method was utilized as the susceptibility test. Candida parapsilosis was the prevailing yeast species recovered from waste, followed by Rhodotorula glutinis. Three strains of Candida guilliermondii presented minimal inhibitory concentration values considered to be susceptible dose dependent (2 μg ml^?1) to voriconazole. Of all airborne fungal species, 69% were recovered from the waste storage room and 31% were recovered from the clinical/surgical environment. Most of them were identified as Cladosporium spp. Conclusions: These findings reinforce the potential risk of waste handling and point out the need for safe management to minimize the spread of these agents to the environment. Filamentous fungi isolation in almost all sampled environments indicates that a periodic monitoring of airborne microbiota in the dental health care service environment is required. Significance and Impact of the Study: The survival of yeast strains for 48 h suggests that dental waste should be carefully controlled and monitored.     

Low occurrence of multi-antimicrobial and heavy metal resistance in Salmonella enterica from wild birds in the United States

Wild birds are common reservoirs of Salmonella enterica. Wild birds carrying resistant S. enterica may pose a risk to public health as they can spread the resistant bacteria across large spatial scales within a short time. Here, we whole-genome sequenced 375 S. enterica strains from wild birds collected in 41 U.S. states during 1978–2019 to examine bacterial resistance to antibiotics and heavy metals. We found that Typhimurium was the dominant S. enterica serovar, accounting for 68.3% (256/375) of the bird isolates. Furthermore, the proportions of the isolates identified as multi-antimicrobial resistant (multi-AMR: resistant to at least three antimicrobial classes) or multi-heavy metal resistant (multi-HMR: resistant to at least three heavy metals) were both 1.87% (7/375). Interestingly, all the multi-resistant S. enterica (n = 12) were isolated from water birds or raptors; none of them was isolated from songbirds. Plasmid profiling demonstrated that 75% (9/12) of the multi-resistant strains carried resistance plasmids. Our study indicates that wild birds do not serve as important reservoirs of multi-resistant S. enterica strains. Nonetheless, continuous surveillance for bacterial resistance in wild birds is necessary because the multi-resistant isolates identified in this study also showed close genetic relatedness with those from humans and domestic animals.     

Mitigation of Heavy Metal Contamination in Soil via Successive Pig Slurry Application

This study evaluates heavy metal removal associated with phytomass management in a Typic Hapludox after three applications of pig slurry. Like humic acids in pig slurry were characterized through physics and chemical spectroscopy technics. Heavy metal levels were determined in ration that was offered to pigs, anaerobically digested pig slurry, and plant tissues from pig slurry-fertilized black oat (Avena strigosa Schreb.) and ryegrass (Lolium multiflorum Lam.) intercrop. Soil contamination was evaluated by the pseudo-total heavy metal levels in six soil layers and the bioavailable levels in the top soil layer. Results indicate that the ration is the origin of heavy metals in the pig slurry. The approximate levels in the ration were as follows (mg kg^?1): Cu 23.9, Zn 92.02, 153.15, Mn 30.98, Ni 0.23, Pb 10.75, Cr 0.34, Co 0.08, and Cd 0.05. The approximate levels of these metals in the pig slurry were as follows (mg kg^?1): Cu 71.08, Zn 345.67, Fe 83.02, Mn 81.71, Ni 1.13, Pb 4.35, Co 0.28, and Cd 0.16. Like humic acids contained 55% aliphatic chains, 14% oxygenated aliphatic chains, and 15% carboxyls, demonstrating their high capacity for interaction with heavy metals by forming soluble complexes. Soil contamination was indicated by the accumulation of heavy metals in the six soil layers in relation to the applied pig slurry dose (ranged as follows (mg kg^?1): Cu 110 to 150, Zn 50 to 120, Ni 20 to 40, and Pb 12 to 16) and as bioavailable forms (levels ranged as follows (mg kg^?1): Cu < 1, Zn 1.0–1.5, Ni 0.1–1.5, and Pb 1.9–6.3). The positive correlation between heavy metal accumulation in the plants and soil bioavailable heavy metal levels and the lowest heavy metal levels under higher intensity of phytomass removal demonstrate the ability of phytomass management to reduce soil contamination.