Screening and molecular identification of heavy metal resistant Pseudomonas putida S4 in tannery effluent wastewater

Removal of Heavy Metals by Pseudomonas sp. - Model Fitting and Interpretation

Industrial and urban modernization processes generate significant amounts of heavy metal wastewater, which brings great harm to human production and health. The biotechnology developed in recent years has gained increasing attention in the field of wastewater treatment due to its repeatable regeneration and lack of secondary pollutants. Pseudomonas, being among the several bacterial biosorbents, possesses notable benefits in the removal of heavy metals. These advantages encompass its extensive adsorption capacity, broad adaptability, capacity for biotransformation, potential for genetic engineering transformation, cost-effectiveness, and environmentally sustainable nature. The process of bacterial adsorption is a complex phenomenon involving several physical and chemical processes, including adsorption, ion exchange, and surface and contact phenomena. A comprehensive investigation of parameters is necessary in order to develop a mathematical model that effectively measures metal ion recovery and process performance. The aim of this study was to explore the latest advancements in high-tolerance Pseudomonas isolated from natural environments and evaluate its potential as a biological adsorbent. The study investigated the adsorption process of this bacterium, examining key factors such as strain type, contact time, initial metal concentration, and pH that influenced its effectiveness. By utilizing dynamic mathematical models, the research summarized the biosorption process, including adsorption kinetics, equilibrium, and thermodynamics. The findings indicated that Pseudomonas can effectively purify water contaminated with heavy metals and future research will aim to enhance its adsorption performance and expand its application scope for broader environmental purification purposes.

Recent Development in Nanoparticle-Assisted Microbial Fuel Cell for Enhanced Reduction of Chromium

Chromium metal is a potential toxin released by various industries as by products. Reduction of the same costs an ample amount of manpower and wealth. Alternate, economical, efficient, and sustainable form of chromium reduction while generating electricity is a boon that microbial fuel cell (MFC) has provided to man. It paves way for an attractive technique to process hazardous elements. Nature as well as the type of electrode modulates the efficiency of reduction and power production. Many previously published studies have reviewed chromium removal from effluents as well as through MFCs, but utilization of nanoparticle-based MFC for chromium removal has not been exclusively done before. Hence, the objective of the current review is to provide exclusive study on nanoparticle-assisted MFC for chromium reduction. Reputed published data from the past 5 years have been studied meticulously to compare the best outcomes of MFC in chromium removal. Chromium is found to be removed mostly in double-chambered MFC with a maximum removal of 100% when iron is used as an electrode. Removal of the same has led to generation of maximum power of 1965.4 mW m-2 when palladium nanoparticles are used at the electrode. Removal rates of Cr(VI) from a mixture of NiCo2O4, MoS2, and graphite felt in a dual-chamber MFC showed an 8.13% increase after 24 h of light exposure. Another efficient setup used MoS2 nanosheets and Alpha-FeOOH nanoparticles in a dual-chamber MFC to completely remove Cr(VI) and achieve a high removal ratio of 91.45%. The current study reviews the recent updates in chromium reduction through MFC and its significance in future as a potential instrument for bioremediation and energy source.

Unboxing PGPR-mediated management of abiotic stress and environmental cleanup: what lies inside?

Abiotic stresses including heavy metal toxicity, drought, salt and temperature extremes disrupt the plant growth and development and lowers crop output. Presence of environmental pollutants further causes plants suffering and restrict their ability to thrive. Overuse of chemical fertilizers to reduce the negative impact of these stresses is deteriorating the environment and induces various secondary stresses to plants. Therefore, an environmentally friendly strategy like utilizing plant growth-promoting rhizobacteria (PGPR) is a promising way to lessen the negative effects of stressors and to boost plant growth in stressful conditions. These are naturally occurring inhabitants of various environments, an essential component of the natural ecosystem and have remarkable abilities to promote plant growth. Furthermore, multifarious role of PGPR has recently been widely exploited to restore natural soil against a range of contaminants and to mitigate abiotic stress. For instance, PGPR may mitigate metal phytotoxicity by boosting metal translocation inside the plant and changing the metal bioavailability in the soil. PGPR have been also reported to mitigate other abiotic stress and to degrade environmental contaminants remarkably. Nevertheless, despite the substantial quantity of information that has been produced in the meantime, there has not been much advancement in either the knowledge of the processes behind the alleged positive benefits or in effective yield improvements by PGPR inoculation. This review focuses on addressing the progress accomplished in understanding various mechanisms behind the protective benefits of PGPR against a variety of abiotic stressors and in environmental cleanups and identifying the cause of the restricted applicability in real-world.

Bioremediation of Cr(VI) using indigenous bacterial strains isolated from a common industrial effluent treatment plant in Vishakhapatnam

The present study focuses on removing hexavalent chromium (Cr(VI)) using indigenous metal-resistant bacterial strains isolated from a common industrial effluent treatment plant, a contaminated site in Vishakhapatnam. Three high metal-resistant isolates were screened by growing them in nutrient agar media containing different Cr(VI) concentrations for 24 h at 35 ± 2 °C. The three strains' minimum inhibitory concentrations of Cr(VI) were examined at neutral pH and 35 ± 2 °C temperature. Morphological, biochemical, and molecular characterizations were carried out, and the strains were identified as Bacillus subtilis NITSP1, Rhizobium pusense NITSP2, and Pseudomonas aeruginosa NITSP3. Elemental composition and functional group analysis of the native and metal-loaded cells were done using energy-dispersive spectroscopy and Fourier-transform infrared spectroscopy, respectively. The operating conditions were optimized using a one-factor-at-a-time analysis. When compared with three bacterial isolates, maximum Cr(VI) removal (80.194 ± 4.0%) was observed with Bacillus subtilis NITSP1 with an initial Cr(VI) concentration of 60 mg/L, pH 7.0, an inoculum size of 2% (v/v), and an incubation period of 24 h. The logistic model was used to predict the variation of biomass growth with time. The present study can be extended to remove heavy metals from industrial wastewater in an environmental-friendly manner.

Toxicity assessment of heavy metal (Pb) and its bioremediation by potential bacterial isolates

Lead (Pb) is a non-essential metal with high toxicity, is persistent, is not biodegradable, and has no known biological function. It is responsible for severe health and environmental issues that need appropriate remediation. Therefore, microbes have thrived in a lead-contaminated environment without exhibiting any negative impacts. The present study aimed to examine the toxic effects of lead on animals and the isolation, identification, and characterization of lead-resistant bacterial strains and their biodegradation potential. After oral administration of lead for 4 weeks, mice showed an elevated level of leukocytes and a decrease in TEC, Hb, PCV, MCV, MCH, and MCHC levels. However, a decline in body weight and inflammation and oxidative stress was observed in liver tissues. To remediate toxic heavy metal, lead-resistant bacterial strains were isolated, among which Enterobacter exhibited maximum degradation potential at high lead concentrations. It was identified by molecular basis and after 16S rRNA sequencing, and 99% resemblance was observed with Enterobacter cloacae. FT-IR analysis of the bacteria illustrated the presence of functional groups, including hydroxyl, carboxyl group, sulfide, and amino groups, on the bacterial cell surface involved in the adsorption of lead. Moreover, electron microscopy (SEM) revealed the morphological and physiochemical changes in the bacterial cell after biosorption, indicating the interaction of Cu ions with functional groups. To summarize, the findings show the highly toxic effects of lead on animals and humans and its effective biodegradation by the bacterial strains in the lead-contaminated environment. This biological strategy can be an ideal alternative to remediate heavy metals from contaminated sites to clean up the environment.

Copper removal capability and genomic insight into the lifestyle of copper mine inhabiting Micrococcus yunnanensis GKSM13

Heavy metal pollution in mining areas is a serious environmental concern. The exploration of mine-inhabiting microbes, especially bacteria may use as an effective alternative for the remediation of mining hazards. A highly copper-tolerant strain GKSM13 was isolated from the soil of the Singhbhum copper mining area and characterized for significant copper (Cu) removal potential and tolerance to other heavy metals. The punctate, yellow-colored, coccoid strain GKSM13 was able to tolerate 500 mg L^-1 Cu²⁺. Whole-genome sequencing identified strain GKSM13 as Micrococcus yunnanensis, which has a 2.44 Mb genome with 2176 protein-coding genes. The presence of putative Cu homeostasis genes and other heavy metal transporters/response regulators or transcription factors may responsible for multi-metal resistance. The maximum Cu²⁺ removal of 89.2% was achieved at a pH of 7.5, a temperature of 35.5 °C, and an initial Cu²⁺ ion concentration of 31.5 mg L^-1. Alteration of the cell surface, deposition of Cu²⁺ in the bacterial cell, and the involvement of hydroxyl, carboxyl amide, and amine groups in Cu²⁺ removal were observed using microscopic and spectroscopic analysis. This study is the first to reveal a molecular-based approach for the multi-metal tolerance and copper homeostasis mechanism of M. yunnanensis GKSM13.

Effective Usage of Biochar and Microorganisms for the Removal of Heavy Metal Ions and Pesticides

The bioremediation of heavy metal ions and pesticides is both cost-effective and environmentally friendly. Microbial remediation is considered superior to conventional abiotic remediation processes, due to its cost-effectiveness, decrement of biological and chemical sludge, selectivity toward specific metal ions, and high removal efficiency in dilute effluents. Immobilization technology using biochar as a carrier is one important approach for advancing microbial remediation. This article provides an overview of biochar-based materials, including their design and production strategies, physicochemical properties, and applications as adsorbents and support for microorganisms. Microorganisms that can cope with the various heavy metal ions and/or pesticides that enter the environment are also outlined in this review. Pesticide and heavy metal bioremediation can be influenced by microbial activity, pollutant bioavailability, and environmental factors, such as pH and temperature. Furthermore, by elucidating the interaction mechanisms, this paper summarizes the microbe-mediated remediation of heavy metals and pesticides. In this review, we also compile and discuss those works focusing on the study of various bioremediation strategies utilizing biochar and microorganisms and how the immobilized bacteria on biochar contribute to the improvement of bioremediation strategies. There is also a summary of the sources and harmful effects of pesticides and heavy metals. Finally, based on the research described above, this study outlines the future scope of this field.

Biosorption of heavy metals by microorganisms: Evaluation of different underlying mechanisms

Globally, ecotoxicologists, environmental biologists, biochemists, pathologists, and other experts are concerned about environmental contamination. Numerous pollutants, such as harmful heavy metals and emerging hazardous chemicals, are pervasive sources of water pollution. Water pollution and sustainable development have several eradication strategies proposed and used. Biosorption is a low-cost, easy-to-use, profitable, and efficient method of removing pollutants from water resources. Microorganisms are effective biosorbents, and their biosorption efficacy varies based on several aspects, such as ambient factors, sorbing materials, and metals to be removed. Microbial culture survival is also important. Biofilm agglomerates play an important function in metal uptake by extracellular polymeric molecules from water resources. This study investigates the occurrence of heavy metals, their removal by biosorption techniques, and the influence of variables such as those indicated above on biosorption performance. Ion exchange, complexation, precipitation, and physical adsorption are all components of biosorption. Between 20 and 35 °C is the optimal temperature range for biosorption efficiency from water resources. Utilizing living microorganisms that interact with the active functional groups found in the water contaminants might increase biosorption efficiency. This article discusses the negative impacts of microorganisms on living things and provides an outline of how they affect the elimination of heavy metals.

Study on the performance of carbonate-mineralized bacteria combined with eggshell for immobilizing Pb and Cd in water and soil

Microbially induced carbonate precipitation (MICP) is an advanced bioremediation approach to remediate heavy metal (HM)-contaminated water and soil. In this study, metal-tolerant urease-producing bacterial isolates, namely, UR1, UR16, UR20, and UR21, were selected based on their urease activity. The efficiency of these isolates in water for Pb and Cd immobilizations was explored. Our results revealed that UR21 had the highest removal rates of Pb (81.9%) and Cd (65.0%) in solution within 72 h through MICP. The scanning electron microscopy-energy-dispersive x-ray and x-ray diffraction analysis confirmed the structure and the existence of PbCO3 and CdCO3 crystals in the precipitates. In addition, the strain UR21, in combination with urea/eggshell waste (EGS) or both, was further employed to investigate the effect of MICP on soil enzymatic activity, chemical fractions, and bioavailability of Pb and Cd. The outcomes indicated that the applied treatments reduced the proportion of soluble-exchangeable-Pb and -Cd, which resulted in an increment in carbonate-bound Pb and Cd in the soil. The DTPA-extractable Pb and Cd were reduced by 29.2% and 25.2% with the treatment of UR21+urea+EGS as compared to the control. Besides, the application of UR21 and EGS significantly increased the soil pH, cation exchange capacity, and enzyme activities. Our findings may provide a novel perceptive for an eco-friendly and sustainable approach to remediate heavy metal-contaminated environment through a combination of metal-resistant ureolytic bacterial strain and EGS.

Evidence of Resistance of Heavy Metals from Bacteria Isolated from Natural Waters of a Mining Area in Mexico

This study focuses on identifying relationships between the content of heavy metals in water and the resistance patterns of different bacteria. Samples from watercourses in one of the most important mining areas in Mexico were collected. Seventy-one bacteria were isolated, and their resistance to Cr, Zn, Cu, Ag, Hg, and Co was studied. The Minimum Inhibitory Concentration range was determined, and a Multiple Metal Resistant index was calculated. After that, 11 isolated bacteria were chosen to estimate kinetic parameters. The obtained results show differences in the behavior of the studied bacteria concerning the presence of heavy metals in the media: (1) without effect, (2) inhibited growth; and (3) considerable inhibited growth. Finally, a Performance Index was proposed to select adequate bacteria for heavy metals removal; five bacteria were selected. Among them, Pseudomonas koreensis was identified as a good candidate for a future biosorption system since these bacteria can stimulate growth in the presence of all the metals tested.

Effective removal of heavy metals from industrial effluent wastewater by a multi metal and drug resistant Pseudomonas aeruginosa strain RA-14 using integrated sequencing batch reactor

Sequencing batch reactor (SBR) is useful in removal of both non-biodegradable and biodegradable contaminants from wastewater. The main aim of the present investigation was to evaluate the potential of biocatalyst strain RA-14 on heavy metal removal under SBR. The selected strain was screened from the soil sediment contaminated with heavy metals. It was able to survive at different (Hg²⁺, Pb²⁺, Zn²⁺, Cu²⁺, Cd²⁺ and Ni²⁺) heavy metals (>500 ppm). The bacterial strain RA-14 showed maximum bioaccumulation potential than other strains. Heavy metal resistance patterns of Pb²⁺ > Cu² > Cd²⁺ > Hg²⁺, Ni²⁺ and Zn² was observed. Strain RA-14 was resistant to penicillin-G, nalidixic acid, ceftazidime, cefotaxime, kanamycin and ampicillin. The results revealed that bioaccumulation activities were improved at pH 7.0 (83.2 ± 1.8%), 40 °C (89.34 ± 3%) and affected at higher pH values and temperature. The results showed that contact time and initial Lead concentration was also affected Lead accumulation. The heavy metal tolerant strain RA-14 was further investigated towards heavy metal removal in SBR. Heavy metal was removed in SBR within 10 h of hydraulic retention time. Heavy metal removal was high at 2 mg/L (0.33 mg/L Cu²⁺, 0.33 mg/L Hg²⁺, 0.33 mg/L Pb²⁺, 0.33 mg/L Zn²⁺, 0.33 mg/L Cd²⁺ and 0.33 mg/L Ni²⁺) heavy metals. Total nitrogen, biological oxygen demand (BOD) and chemical oxygen demand (COD) of treated water in SBR was removed and the removal efficacy was 91.3 ± 2.1%, 97.6 ± 3.3%, and 94.3 ± 4.4%, respectively in 10 h hydraulic retention time. However, the efficiency of BOD, COD and total nitrogen content removal was decreased, due to the reduced metabolic process of bacteria after 10 h. The SBR reactor proved to be an efficient method for the treatment of various heavy metals from the wastewater.

Chromium contamination and effect on environmental health and its remediation: A sustainable approaches

Chromium (Cr) is a trace element critical to human health and well-being. In the last few decades, its contamination, especially hexavalent chromium [Cr(VI)] form in both terrestrial and aquatic ecosystems, has amplified as a result of various anthropogenic activities. Chromium pollution is a significant environmental threat, severely impacting our environment and natural resources, especially water and soil. Excessive exposure could lead to higher levels of accumulation in human and animal tissues, leading to toxic and detrimental health effects. Several studies have shown that chromium is a toxic element that negatively affects plant metabolic activities, hampering crop growth and yield and reducing vegetable and grain quality. Thus, it must be monitored in water, soil, and crop production system. Various useful and practical remediation technologies have been emerging in regulating chromium in water, soil, and other resources. A sustainable remediation approach must be adopted to balance the environment and nature.

Lead bioaccumulation mediated by Bacillus cereus BPS-9 from an industrial waste contaminated site encoding heavy metal resistant genes and their transporters

This study explores the soil microorganisms for their Lead bioremediation capability. The MIC values of the six Lead resistant bacteria were evaluated, and the AAS studies of these isolates estimated their Lead accumulation percentage. The results showed that the isolate namely Bacillus cereus BPS-9 as identified based on 16S rDNA gene sequences was shown to have the highest Lead accumulation potential (79.26 %) and also selected for bioaccumulation studies. Despite the reduction in growth rate, the superoxide dismutase activity of B. cereus BPS-9 was increased with a rise in the concentration of Lead manifested through increased nitro-blue tetrazolium (NBT) reduction from 3.94 % to 77.48 %. Moreover, the biosorption capacity of B. cereus BPS-9 was 193.93 mg/g and the Langmuir isotherm model showed a value of R² = 0.9. Furthermore, the FTIR analysis also established the role of C-H, C=C, N=N, N-H, and C-O functional groups in Lead adsorption and the SEM micrographs showed that the cells of B. cereus BPS-9 became dense, adhered and distorted after Lead adsorption. Finally, the In-silico results obtained by functional analysis through SEED viewer of the whole genome of B. cereus deciphered the presence of genes encoding heavy metal resistant proteins and transporters for the efflux of heavy metals.

Unlocking the potential of plant growth-promoting rhizobacteria on soil health and the sustainability of agricultural systems

The concept of soil health refers to specific soil properties and the ability to support and sustain crop growth and productivity, while maintaining long-term environmental quality. The key components of healthy soil are high populations of organisms that promote plant growth, such as the plant growth promoting rhizobacteria (PGPR). PGPR plays multiple beneficial and ecological roles in the rhizosphere soil. Among the roles of PGPR in agroecosystems are the nutrient cycling and uptake, inhibition of potential phytopathogens growth, stimulation of plant innate immunity, and direct enhancement of plant growth by producing phytohormones or other metabolites. Other important roles of PGPR are their environmental cleanup capacities (soil bioremediation). In this work, we review recent literature concerning the diverse mechanisms of PGPR in maintaining healthy conditions of agricultural soils, thus reducing (or eliminating) the toxic agrochemicals dependence. In conclusion, this review provides comprehensive knowledge on the current PGPR basic mechanisms and applications as biocontrol agents, plant growth stimulators and soil rhizoremediators, with the final goal of having more agroecological practices for sustainable agriculture.