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The current research was performed to evaluate the effect ofBacillus megateriumMCR-8 on mitigation of nickel (Ni) stress inVinca roseagrown on Ni-contaminated soil (50, 100, and 200 mg Ni kg−1soil). The treated plants exhibited reduced growth, biomass, gas exchange capacity, and chlorophyll (Chl) content under Ni stress. The inoculated plants growing in Ni-contaminated media exhibited relatively higher growth, total soluble protein, and proline contents. Similarly, bacterial inoculation improved the activity of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) under Ni stress. The Ni stress alleviation in inoculated plants was attributed to the reduced level of malondialdehyde (MDA) and hydrogen peroxide (H2O2), enhanced synthesis of protein, proline, phenols, and flavonides in conjunction with improved activity of antioxidant enzymes. The growth-promoting characteristics of microbe such as 1-aminocyclopropane-1-carboxylate deaminase (ACCD) and phosphate solubilization activity, siderophore, and auxin production capability also improved the growth and stress mitigation in inoculated plants. Furthermore, the inoculated plants exhibited higher value for bioconcentration factor (BCF), translocation factor (TF), and resulted in higher loss of Ni content from soil. The current results exhibited the beneficial role ofB. megateriumMCR-8 regarding stress alleviation and Ni phytoextraction byV. rosea. [ABSTRACT FROM AUTHOR]

Microbes have shown potential for the bioremediation of tannery waste polluted soil. During our previous study, it was observed that heavy metal resistant Burkholderia cepacia CS8 augmented growth and phytoremediation capability of an ornamental plant. Objective of the present research work was to evaluate the capability of B. cepacia CS8 assisted Calendula officinalis plants for the phytoremediation of tannery solid waste (TSW) polluted soil. The TSW treatment significantly reduced growth attributes and photosynthetic pigments in C. officinalis. However, supplementation of B. cepacia CS8 which exhibited substantial tolerance to the TSW amended soil, augmented growth traits, carotenoid, proline, and antioxidant enzymes level in C. officinalis under toxic and nontoxic regimes. Inoculation of B. cepacia CS8 augmented plant growth (shoot length 13%, root length 11%), physiological attributes (chlorophyll a 14%, chlorophyll b 17%), antioxidant enzyme activities (peroxidase 24%, superoxide dismutase 31% and catalase 19%), improved proline 36%, phenol 32%, flavonoids 14% and declined malondialdehyde (MDA) content 15% and hydrogen peroxide (H2O2) level 12% in C. officinalis at TSW10 stress compared with relevant un-inoculated plants of TSW10 treatment. Moreover, B. cepacia CS8 application enhanced labile metals in soil and subsequent metal uptake, such as Cr 19%, Cd 22%, Ni 35%, Fe 18%, Cu 21%, Pb 34%, and Zn 30%, respectively in C. officinalis plants subjected to TSW10 stress than that of analogous un-inoculated treatment. Higher plant stress tolerance and improved phytoremediation potential through microbial inoculation will assist in the retrieval of agricultural land in addition to the renewal of native vegetation. During the current study, it was observed that combination of Calendula officinalis and metal tolerant Burkholderia cepacia CS8 not only improved plant growth but also helped phyto-extraction of pollutants present in the tannery solid waste polluted soil. According to our information, research work describing the phytoremediation potential of native metal tolerant microbes and ornamental plants has not been reported in Pakistan. [ABSTRACT FROM AUTHOR]

The remediation of heavy metal-contaminated soils has become a critical issue due to toxic effects of these metals on living organisms. The current research was conducted to study the effect ofPseudomonas fluorescensRB4 andBacillus subtilis189 on the growth and phytoremediation potential ofCatharanthus roseusin Cu- and Pb-contaminated soils. The bacterial strains exhibited significantly higher level of water-extractable Pb and Cu in Pb, Cu, and Cu+Pb-contaminated. TheP. fluorescensRB4 inoculated plants, produced 102%, 48%, and 45% higher fresh weight (FW) in soils contaminated with Cu, Pb, and both elements, respectively, as compared to un-inoculated control plants. Similarly,B. subtilis189 inoculated plants produced 108%, 43%, and 114% more FW in the presence of Cu, Pb, and both elements. The plants co-cultivated with both bacteria exhibited 121%, 102%, and 177% higher FW, in Cu, Pb, and both elements contaminated soils, as compared to respective un-inoculated control. Co-cultivation ofP. fluorescensRB4, B. subtilis189, andP. fluorescensRB4 +B. subtilis189 resulted in higher accumulation of Cu and Pb in shoots of theC. roseusgrown in contaminated soils as compared to un-inoculated control. Bacterial treatments also improved the translocation and metal bioconcentration factors. The growth and phytoextraction capability ofC. roseuswas improved by inoculation ofP. fluorescensRB4 andB. subtilis189. [ABSTRACT FROM AUTHOR]

Some rhizobacteria are capable of improving metal tolerance and growth of plants under heavy metal stress. The objective of the current study was isolation and subsequent application of cadmium-resistant rhizobacteria in phytoremediation by Catharanthus longifolius. The screened bacterial isolate exhibited growth-promoting attributes, including phosphate solubilization, ACCD activity, auxin, and siderophores production. The inoculation of Acinetobacter sp. CS9 under greenhouse trial improved growth and phytoextraction capability of C. longifolius plants in soils contaminated with different concentrations (0, 100, and 200 mg kg-1) of Cd. The plants exhibited reduced quantity of total soluble protein, soluble sugars, and chlorophyll contents under Cd stress. On the other hand, improved chlorophyll, soluble protein, and sugar contents were observed in Acinetobacter sp. CS9-treated plants. The inoculated plants exhibited improved activity of antioxidant enzymes (SOD and CAT) and reduced malondialdehyde levels. Moreover, higher Cd uptake and translocation ratio was observed in Acinetobacter sp. CS9-inoculated plants as compared to un-inoculated ones. The current study showed that Acinetobacter sp. CS9 reduced Cd-induced oxidative stress and improved the phytoremediation capability of C. longifolius. [ABSTRACT FROM AUTHOR]

During our current study we evaluated the effect of ethylenediaminetetracetic acid (EDTA) and Enterobacter sp. CS2 on nickel stress alleviation and phytoextraction by Impatiens balsamina L in spiked soil. Nickel resistant Enterobacter sp. CS2 was isolated from soil polluted by industrial effluents. The I. balsamina seeds primed with Enterobacter sp. CS2 were raised in EDTA-supplemented soil (10 mM) contaminated with 0, 100, 200, and 300 mg kg-1 Ni for 50 days. The effect of different treatments on plant growth attributes, nickel tolerance index, bioconcentration factor, and translocation factor were evaluated. The Ni stress reduced plant growth, carotenoids, and chlorophyll (chl) content. However, higher Ni uptake and proline contents were observed in plants growing in Ni-contaminated soils. The Enterobacter sp. CS2 inoculation further enhanced Ni uptake and proline contents in I. balsamina plants growing under Ni stress. The inoculated plants showed improved shoot length, root length, carotenoid content, chl 'a' and 'b' contents, root and shoot dry weight. The Ni tolerance index in Enterobacter sp. CS2-assisted plants was much higher compared to un-inoculated ones. The inoculated plants supplemented with EDTA enhanced 39%, 34%, and 30% Ni uptake in roots respectively under 100, 200, and 300 mg kg-1 of Ni treatment as compared with un-inoculated plants. The data regarding bioconcentration factor and translocation factor showed that Ni phytoextraction capability of I. balsamina plants was significantly enhanced with the supplementation of Enterobacter sp. CS2 and EDTA. [ABSTRACT FROM AUTHOR]

The current study was performed to assess the effect of Burkholderia cepacia CS8 on the phytoremediation of cadmium (Cd) by Catharanthus roseus grown in Cd-contaminated soil. The plants cultivated in Cd amended soil showed reduced growth, dry mass, gas-exchange capacity, and chlorophyll contents. Furthermore, the plants exhibited elevated levels of malondialdehyde (MDA) and hydrogen peroxide (H2O2) under Cd stress. The bacterized plants showed higher shoot length, root length; fresh and dry weight. The improved stress tolerance in inoculated plants was attributed to the reduced quantity of MDA and H2O2, enhanced synthesis of protein, proline, phenols, flavonoids, and improved activity of antioxidant enzymes including peroxidase, superoxide dismutase, ascorbate peroxidase, and catalase. Similarly, the 1-aminocyclopropane-1-carboxylate deaminase activity, phosphate solubilization, auxin, and siderophore production capability of B. cepacia CS8 improved growth and stress alleviation in treated plants. The bacterial inoculation enhanced the amount of water extractable Cd from soil. Furthermore, the inoculated plants showed higher bioconcentration factor and translocation factor. The current study exhibits that B. cepacia CS8 improves stress alleviation and phytoextraction potential of C. roseus plants growing under Cd stress. [ABSTRACT FROM AUTHOR]

In our current study, four nickel-tolerant (Ni-tolerant) bacterial species viz,Bacillus thuringiensis002,Bacillus fortis162,Bacillus subtilis174, andBacillus farraginis354, were screened using Ni-contaminated media. The screened microbes exhibited positive results for synthesis of indole acetic acid (IAA), siderophore production, and phosphate solubilization. The effects of these screened microbes on Ni mobility in the soil, root elongation, plant biomass, and Ni uptake inAlthea roseaplants grown in Ni-contaminated soil (200 mg Ni kg−1) were evaluated. Significantly higher value for water-extractable Ni (38 mg kg−1) was observed in case of Ni-amended soils inoculated withB. subtilis174. Similarly,B. thuringiensis002,B. fortis162, andB. subtilis174 significantly enhanced growth and Ni uptake inA. rosea. The Ni uptake in the shoots and roots ofB. subtilis174-inoculated plants enhanced up to 1.7 and 1.6-fold, respectively, as compared to that in the un-inoculated control. Bacterial inoculation also significantly improved the root and shoot biomass of treated plants. The current study presents a novel approach for bacteria-assisted phytoremediation of Ni-contaminated areas. [ABSTRACT FROM PUBLISHER]