Bioremediation of Heavy Metals by a Novel Bacterial Strain Enterobacter cloacae and Its Antioxidant Enzyme Activity, Flocculant Production, and Protein Expression in Presence of Lead, Cadmium, and Nickel

Banerjee, Goutam; Pandey, Shubhant; Ray, Arun Kumar; Kumar, Ravi

doi:10.1007/s11270-015-2359-9

Cited by 86 publications

(30 citation statements)

References 33 publications

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“…Bacteria belonging to the genus Enterobacter have been found to associate frequently with a large number of plant species, colonizing the rhizosphere and other plant parts (63)(64)(65)(66). Moreover, several metal-resistant Enterobacter species, including some with PGP effects, have been isolated, and some of their characteristics in response to metals have been determined (67)(68)(69)(70)(71)(72). However, investigations of their metal response systems at the global regulatory level are limited.…”

Section: Discussionmentioning

confidence: 99%

Survival Strategies of the Plant-Associated Bacterium Enterobacter sp. Strain EG16 under Cadmium Stress

Chen

Chao

et al. 2016

Appl Environ Microbiol

113

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c Plant-associated bacteria are of great interest because of their potential use in phytoremediation. However, their ability to survive and promote plant growth in metal-polluted soils remains unclear. In this study, a soilborne Cd-resistant bacterium was isolated and identified as Enterobacter sp. strain EG16. It tolerates high external Cd concentrations (Cd 2؉ MIC, >250 mg liter ؊1 ) and is able to produce siderophores and the plant hormone indole-3-acetic acid (IAA), both of which contribute to plant growth promotion. Surface biosorption in this strain accounted for 31% of the total Cd accumulated. The potential presence of cadmium sulfide, shown by energy-dispersive X-ray (EDX) analysis, suggested intracellular Cd binding as a Cd response mechanism of the isolate. Cd exposure resulted in global regulation at the transcriptomic level, with the bacterium switching to an energyconserving mode by inhibiting energy-consuming processes while increasing the production of stress-related proteins. The stress response system included increased import of sulfur and iron, which become deficient under Cd stress, and the redirection of sulfur metabolism to the maintenance of intracellular glutathione levels in response to Cd toxicity. Increased production of siderophores, responding to Cd-induced Fe deficiency, not only is involved in the Cd stress response systems of EG16 but may also play an important role in promoting plant growth as well as alleviating the Cd-induced inhibition of IAA production. The newly isolated strain EG16 may be a suitable candidate for microbially assisted phytoremediation due to its high resistance to Cd and its Cd-induced siderophore production, which is likely to contribute to plant growth promotion. Heavy metal contamination has become one of the most serious environmental problems in recent years. Metal extraction activities are major sources for heavy metals in the environment (1). Cadmium is highly toxic to plants, animals, microorganisms, and humans even at quite low concentrations (2, 3). Although Cd is non-redox active, it can cause oxidative stress by generating reactive oxygen species (ROS) (4), which can lead to DNA damage (5), inhibit the DNA mismatch repair system (6), and disrupt the synthesis of nucleic acids and proteins (7).Phytoremediation, a low-cost and eco-friendly technology for the decontamination of heavy-metal-polluted soils, uses plants to absorb, accumulate, and detoxify heavy metals in soil (3). However, the serious environmental stresses present in most cases of phytoremediation result in slow plant growth, low biomass production, and long time frames for remediation, limiting the usefulness of this technology (8). Beneficial plant-associated bacteria have been shown to protect plants from metal toxicity and promote plant growth. The plant growth-promoting (PGP) characteristics that most of these bacteria possess, including N 2 fixation, siderophore production, the production of plant growth hormones, such as indole-3-acetic acid (IAA), and the reduction of ethylen...

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Section: Discussionmentioning

confidence: 99%

Survival Strategies of the Plant-Associated Bacterium Enterobacter sp. Strain EG16 under Cadmium Stress

Chen

Chao

et al. 2016

Appl Environ Microbiol

113

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“…The Student's t-test or ANOVA with Tukey's test as the post hoc analysis was carried out to compare means of groups. 900 and 1,100 ppm, respectively (Banerjee et al 2015). This phenomenon suggested that being heavy metal tolerant and conducting heavy metal reduction are part of the strategies employed by bacteria from this genus to combat heavy metal toxicity.…”

Section: Discussionmentioning

confidence: 95%

ISOLATION AND CHARACTERIZATION OF A MOLYBDENUM-REDUCING AND PHENOLIC- AND CATECHOL-DEGRADING Enterobacter sp. STRAIN SAW-2

Sabullah

Rahman²,

Ahmad³

et al. 2017

BIOTROPIA

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Molybdenum is an emerging pollutant worldwide. The objective of this study is to isolate molybdenum-reducing bacterium with the ability to grow on phenolic compounds (phenol and catechol). The screening process was carried out on a microplate. The bacterium reduced molybdenum in the form of sodium molybdate to molybdenum blue (Mo-blue). The bacterium required a narrow pH range for optimal reduction of molybdenum, i.e. between pH 6.3 and o 6.8, with temperature between 34 and 37 C. Molybdate reduction to Mo-blue was best supported by glucose as the carbon source. However, both phenol and catechol could not support molybdate reduction. Other requirements for molybdate reduction included sodium molybdate concentrations between 15 and 30 mM, and phosphate concentration of 5.0 mM. The bacterium exhibited a Mo-blue absorption spectrum with a shoulder at 700 nm and a maximum peak near the infrared region at 865 nm. The Mo-reducing bacterium was partially identified as Enterobacter sp. strain Saw-2. The capability of this bacterium to grow on toxic phenolic compounds and to detoxify molybdenum made it a significant agent for bioremediation.

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“…In this work, we found an increase in the planted plots in bacteria able to resist HM stress by producing these protective enzymes. In fact, many bacteria are able to reduce oxidative stress by producing catalase (CAT), superoxide reductase (SOD), peroxidase, glutathione reductase (GR) thioredoxin (Trx) and thioredoxin reductase (TrxRs) [47]. CAT and SOD are able to convert ROS into oxygen and water and make the maintaining of cellular integrity possible [48,49,50].…”

Section: Discussionmentioning

confidence: 99%

Characterization of the belowground microbial community in a poplar-assisted bioremediation strategy for restoring a multi-contaminated soil

Ab¹,

Grenni²,

Gl³

et al. 2020

Preprint

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Background: Due to their widespread use in industrial applications in recent decades, Polychlorobiphenyls (PCBs) and heavy metals (HMs) are the most common soil contaminants worldwide, posing a risk for both ecosystems and human health.Results: a poplar-assisted bioremediation strategy has been applied for more than four years to a historically contaminated area (PCBs and HMs) in Southern Italy using the Monviso poplar clone. This clone was effective in promoting a decrease in all contaminants and an increase in soil quality in terms of organic carbon and microbial abundance. Moreover, a significant shift in the structure and functioning of the belowground microbial community was also observed when analysing both DNA and cDNA sequencing. In fact, an increase in bacterial genera belonging to Proteobacteria and able to degrade PCBs and resist HMs was observed. Moreover, the functional profiling of the microbial community predicted by PICRUSt2 made it possible to identify several genes associated with PCB transformation (e.g. bphAa, bphAb, bphB, bphC), response to HM oxidative stress (e.g. catalase, superoxide reductase, peroxidase) and HM uptake and expulsion (e.g. ABC transporters).Conclusions: This work demonstrated the effectiveness of the poplar clone used in stimulating the natural belowground microbial community to remove contaminants (phyto-assisted bioremediation) and improve the overall soil quality. It is a practical example of a nature based solution involving synergic interactions between plants and the belowground microbial community.

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Bioremediation of Heavy Metals by a Novel Bacterial Strain Enterobacter cloacae and Its Antioxidant Enzyme Activity, Flocculant Production, and Protein Expression in Presence of Lead, Cadmium, and Nickel

Cited by 86 publications

References 33 publications

Survival Strategies of the Plant-Associated Bacterium Enterobacter sp. Strain EG16 under Cadmium Stress

Survival Strategies of the Plant-Associated Bacterium Enterobacter sp. Strain EG16 under Cadmium Stress

ISOLATION AND CHARACTERIZATION OF A MOLYBDENUM-REDUCING AND PHENOLIC- AND CATECHOL-DEGRADING Enterobacter sp. STRAIN SAW-2

Characterization of the belowground microbial community in a poplar-assisted bioremediation strategy for restoring a multi-contaminated soil

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