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Abstract
In a previous study by the authors, toxicity screening of Atrazine-resistant soil bacteria from different contaminated soils resulted in 23-soil isolate best grown in the presence of herbicide Atrazine. They were identified according to their 16S rDNA sequencing into Enterobacter (E. cloacae), Bacillus (B. cereus and B. anthracis),
Pseudom...
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... and biostimulation with citrate as an efficient bioremediation tool for Atrazine-contaminated soils. Also plant species with well- developed fibrous rooting systems are most effective in enhancing degradation rates and increasing microbial counts within their rhizosphere [11]. Co-application of glufosinate with nitrogen fertilizers may alter Atrazine cometabolism and extended the herbicide’s residual weed control in adapted soils [21,22]. Similarly, the presence of other herbicide such as alachlor altered Atrazine persistence in soil compared to other herbicides [23]. The main objective of the present study was to investigate the remediation capability of the indigenous microbial population in loam-sand soil cultivated with corn maize crop and treated with Atrazine. Levels of degradation using enriched soil natural microorganisms in simulated field conditions system was monitored during cultivation course and the dissipation rate of the Atrazine was estimated. Residual concentrations and bioremediation of the herbicide Atrazine were investigated in sandy-loam soils from two completely different environments (Egypt and Saudi Arabia). Atrazine (Figure 1) was selected based on its common use for the protection of corn and cucumber crops from weeds and herbs. Loam Sandy soil samples were collected from two different ecosystems (Hada Al-Shame area, Saudi Arabia (Soil H ) and El-Sharqia Governorate, Egypt (Soil E ) and used in comparative studies for cultivation of corn to investigate the fate of Atrazine, the applied herbicide. Soils were collected from the top layer of the soil profiles (0-20 cm), passed through a 2 mm sieve, and stored in polyethylene bags until used. Twenty three soil indigenous isolates were isolated from different Atrazine- contaminated soils in a previous study by El-Bestawy et al. (2013) [24] (supplementary materials). They were molecularly Page 2 of 7 identified as Enterobacter ( E. cloacae ), Bacillus ( B. cereus and B. anthracis), Pseudomonas (P. aeruginosa, P. balearica, P. indica and P. otitidis), Ochrobactrum (O. intermedium) and Providencia (P. vermicola). Among them seven bacterial species belong to 4 genera (Enterobacter, Pseudomonas, Bacillus and Providencia) were found superior in their resistance to Atrazine when enriched in medium amended with 2-fold (2X RD) the recommended dose (RD) of Atrazine set by the Egyptian and Saudi Agriculture Ministries. Therefore, they considered acclimatized, highly Atrazine -resistant and can efficiently be used for the degradation of Atrazine in contaminated soil and/or wastewater. In addition to the indigenous isolates, three exogenous isolates namely Pseudomonas sp (PF), Providencia sp . (PS) and Bacillus sp . (PQ) provided from the collection of the Institute of Graduate Studies and Research (IGSR), Alexandria University were used in the present study. They were isolated from heavily polluted wastewater and environments. Cultures were maintained at 4°C on nutrient agar slants and transferred monthly. Development of Simulated Natural Soil System: This experiment was performed as a simulation model for natural soil system exposed to repeated applications of Atrazine to determine the possibility to bio- remediate that system under the natural conditions. Two systems (I and II) were developed for the Egyptian and Saudi soils (soil E and soil H ) respectively, cultivated with corn and sprayed with the Atrazine (80% active ingredient) at dose recommended (RD) by the Egyptian and Saudi Agriculture Ministries. Treatability studies took place for 4 weeks in the two bioassays (one for each soil) using 4 cells (for each bioassay). The four cells represent different bioremediation technologies applied to the contaminated soils in the following manner: Cell (I): Control (sterile soil, i.e. no indigenous or exogenous microbes) Cell (II): Biostimulation (i.e. soil with only the indigenous microorganisms+the addition of nutrients). Cell (III): Bioaugmentation (i.e. soil with the indigenous microorganisms augmented by exogenous microorganisms to help the indigenous species in the biodegradation of the herbicide without the addition of nutrients). Cell (IV): A combination between Biostimulation and Bioaugmentation (i.e. indigenous soil microbes+exogenous microorganisms+addition of nutrients). Bioremediation of contaminated Egyptian (Soil E ) and Saudi (Soil H ) in system I and II: Atrazine-free Egyptian (soil E ) and Saudi (soil H ) was divided and dispensed into 8 cells (25x25x15 cm plastic basin each) where different bioremediation technologies were applied. Cell (I) was considered as control with sterile soil autoclaved at 121°C for 20 minutes to kill and prevent the growth of the indigenous microorganisms. In cell (II) biostimulation technology was applied where soil was enriched with nutrients ((NH 4 ) 2 SO 4] and K 2 HPO 4 at 250 and 100 mg/kg respectively) to enhance the growth and activity of the indigenous microorganisms [25]. Bioaugmentation technology was applied to the soil in cell (III) where the most promising indigenous and exogenous Atrazine degraders were seeded at definite ratios to accelerate and help the indigenous bacterial population to achieve high and fast remediation of the contaminated soil. A combination of biostimulation and bioaugmentation technologies was applied to the soil of cell (IV) to investigate the synergistic or suppressive effects ...
Citations
... One of the most widely used herbicides in agriculture is atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) [7][8][9]. It is primarily applied as a selective herbicide for controlling broad-leaf and some grassy weeds in crop production such as corn, maize, pineapple, sorghum and sugar cane [8][9][10][11] and as a non-selective herbicide for non-cropped fallow lands and industrial lands [12]. ...
... One of the most widely used herbicides in agriculture is atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) [7][8][9]. It is primarily applied as a selective herbicide for controlling broad-leaf and some grassy weeds in crop production such as corn, maize, pineapple, sorghum and sugar cane [8][9][10][11] and as a non-selective herbicide for non-cropped fallow lands and industrial lands [12]. Nevertheless, the long-term and excessive HISTORY application of atrazine could lead to its high concentration presence and persistence in the soil which could be dissipated through leaching into ground water and drinking water as well as washed (as run-off) into surface water, if applied prior to irrigation or heavy rainfall [13]. ...
... Atrazine is a non-polar, non-volatile and low soluble compound [8]. It is also a chlorotriazine and has in its structure a hexameric aromatic ring, symmetrical, composed by three carbon atoms and three nitrogen atoms in alternated positions ( Fig. 1). ...
The most feasible and economical technique for removal of toxic compounds in the polluted environment is bioremediation. This technique surpasses other physicochemical methods in recent time for being effective particularly at a lower concentration of the toxicant. In this study, seven (7) previously isolated molybdenum-reducing bacteria were screened for their potential to degrade atrazine herbicide as sole carbon source for growth. Bacterial colony count on mineral salt medium supplemented with atrazine was used for the screening, while the effects of incubation time, concentration, temperature, pH, inoculum size and heavy metals on atrazine biodegradation was used in characterizing the candidate isolate. Of the seven isolates, an isolate identified as Pseudomonas sp. that grew best with a count of 195 CFU/mL was chosen. The optimum conditions supporting atrazine degradation by Pseudomonas sp. were found to be temperature 35 °C, pH 7.0, incubation time 48 hours and 400 µL inoculum. The use of atrazine as carbon and electron donor source for molybdenum reduction, poorly support molybdenum blue (Mo-blue) production. At a concentration (2 ppm), heavy metals such as lead and copper did not significantly (p>0.05) affect atrazine biodegradation relative to control, iron and silver shows a relative stimulatory effect to the process, while mercury and zinc showed significant (p<0.05) inhibitory effect when compared to control. The ability of the isolate to degrade atrazine makes it an important instrument for bioremediation of this herbicide.
... Ethyl acetate was added to rest of culture in 1:1 ratio and shaken well for 30 min. The suspension was filtered through Buchner funnel with a cotton pad followed by centrifugation of filtrate at 3500 rpm for 20 min (El-Bestawy et al., 2014). Other steps of extraction with supernatant are same as described above. ...
Over use of organophosphate pesticides including Chlorpyrifos (CPF) has led to contamination of soil and water resources, resulting in serious health problems in humans along with other non-target organisms. The current study was aimed to investigate Chlorpyrifos as well as 3, 5, 6-Trichloro-2-pyridinol (TCP) biodegradation tendency of bacterial strain Bacillus thuringiensis MB497 isolated from wheat/cotton fields of Dera Saleemabad, Mianwali, Pakistan, having a history of heavy Organophosphate pesticides application. HPLC analysis revealed almost 99% degradation of the spiked CPF (200 mg L⁻¹) in M-9 broth, soil slurry and soil microcosm by MB497 after 9 days of incubation. Strain MB497 was also able to degrade and transform TCP (28 mg L⁻¹), up to 90.57% after 72 h of incubation in M-9 broth. A novel compound Di-isopropyl methanephosphonate along with known products of 3, 5, 6-Trichloro-2-pyridinol (TCP), Diethyl thiophospsphate and Phosphorothioic acid were detected as metabolites of CPF by GCMS analysis. Three novel metabolites of TCP (p-Propyl phenol, 2-Ethoxy-4, 4, 5, 5-tetramethyloxazoline and 3-(2, 4, 5-Trichlorophenoxy)-1-propyne) were identified after 72 h. Based on these metabolites, new/amended metabolic pathways for CPF and TCP degradation in these bacteria has been suggested.
... Pseudomonas balearica is an environmental Gram-negative bacilliform bacterium with denitrifying capabilities and the ability to degrade several organic compounds; such as, naphthalene 1 and thiosulfate; 2 suggesting potential applications in bioremediation. 3 Biochemically, P. balearica and Pseudomonas stutzeri exhibit several common phenotypical traits; 4 such as, starch hydrolysis, maltose utilisation, arginine utilisation, and does not undergo gelatin hydrolysis. As a result, P. balearica was previously considered to be a genomovar of P. stutzeri but an analysis of 16S rRNA sequences 1 suggests that P. balearica should be considered distinct from P. stutzeri. ...
Pseudomonas balearica DSM 6083T has potential applications in bioremediation and its genome is recently sequenced. Codon usage bias is important in the study of evolutionary pressures on the organism and physical properties of peptides may elucidate functional peptides. However, both have not been studied for P. balearica DSM 6083T. Here, we investigated the codon usage bias and peptide properties of the 4,050 coding sequences in P. balearica. Codon usage analysis suggests that all preferred codons were either G or C ending. There is a skew towards smaller peptides and all peptide properties (pI, aromaticity, hydropathy, and instability) are correlated (|r| >0.102, p-value <7 x 10-11). %GC is correlated (|r| >0.122, p-value <6 x 10-15) to peptide length, aromaticity, hydropathy, and instability. Peptide length is correlated (|r| <0.057, p-value <0.0003) to pI, aromaticity, and instability. Codon usage is correlated (r<-0.042, p-value <0.0075) with all peptide properties while amino acid usage is correlated (r<-0.084, p-value <8 x 10-8) to all peptide properties except instability. A substantial proportion (26.9%) of genes show significantly different codon and amino acid ratios compared to the genomic and proteomic averages respectively (p-value <1.2 x 10-5), suggesting potential exogenous origins. These results suggest a complex interplay of metagenomic environment and various genomic/proteomic properties in shaping the evolution of P. balearica DSM 6083T.
... This progressive domestication, which could gradually promote the adaptive capacity of target microorganisms to worse environment, was proved to be effective and enabled us to isolate the novel bacterial consortia of AMQD4, including Providencia vermicola, Brevundimonas diminuta, Alcaligenes sp. and Acinetobacter, for enhanced degradation of gentamicin in submerged fermentation. An important characteristic of AMQD4 is that each bacterial member of the consortia was able to eliminate toxic compounds in the environment 9,15,16 . In addition, in consideration of that AMQD4 was isolated from bio-solids sludge, which is a kind of waste including a great deal of gentamicin residues, AMQD4 could adapt to the environments containing gentamicin and maintain effective gentamicin degradation. ...
Gentamicin, a broad spectrum antibiotic of the aminoglycoside class, is widely used for disease prevention of human beings as well as animals. Nowadays the environmental issue caused by the disposal of wastes containing gentamicin attracts increasing attention. In this study, a gentamicin degrading bacterial consortia named AMQD4, including Providencia vermicola, Brevundimonas diminuta, Alcaligenes sp. and Acinetobacter, was isolated from biosolids produced during gentamicin production for the removal of gentamicin in the environment. The component and structure of gentamicin have a great influence on its degradation and gentamicin C1a and gentamicin C2a were more prone to being degraded. AMQD4 could maintain relatively high gentamicin removal efficiency under a wide range of pH, especially in an alkaline condition. In addition, AMQD4 could remove 56.8% and 47.7% of gentamicin in unsterilized and sterilized sewage in a lab-scale experiment, respectively. And among the isolates in AMQD4, Brevundimonas diminuta BZC3 performed the highest gentamicin degradation about 50%. It was speculated that aac3iia was the gentamicin degradation gene and the main degradation product was 3′-acetylgentamicin. Our results suggest that AMQD4 and Brevundimonas diminuta BZC3 could be important candidates to the list of superior microbes for bioremediation of antibiotic pollution.
Environmental pollution and its remediation are one of the major problems around the globe. Broad varieties of pollutants viz. pesticides, hydrocarbons, heavy metals, and dyes, etc. are the key players, which are mainly responsible for environmental pollution. Residual contaminants are also difficult to eliminate. Bioremediation is one of the most efficient technologies for the reduction of environmental pollutants that recovers the contaminated site back to its actual form. So far only a small number of microbes (culturable microbes) have been exploited and a huge microbial diversity is still unexplored. To enhance the metabolic potential of the microbes, ecological restoration and degradation of recalcitrant pollutants, various bioremediation approaches like chemotaxis, biostimulation, bioaugmentation, biofilm formation, application of genetically engineered microorganisms, advanced omics, have been widely used. In the last few years, the metabolic potential of microbes has tremendously improved the realization of degradation and remediation of environmental pollution. Microorganisms help in the restoration of contaminated habitats by cleaning up waste in a environmentally safe manner along with the production of safe end products. This review discusses the important processes involved in enhancing bioremediation and recent advances in microbes and plants associated bioremediation.
