Effects of Interfaces of Goethite and Humic Acid-Goethite Complex on Microbial Degradation of Methyl Parathion

Nanocolloids in the soil environment: Transformation, transport and ecological effects

Nanocolloids (Ncs) are ubiquitous in natural systems and play a critical role in the biogeochemical cycling of trace metals and the mobility of organic pollutants. However, the environmental behavior and ecological effects of Ncs in the soil remain largely unknown. The accumulation of Ncs may have detrimental or beneficial effects on different compartments of the soil environment. This review discusses the major transformation processes (e.g., agglomeration/aggregation, absorption, deposition, dissolution, and redox reactions), transport, bioavailability of Ncs, and their roles in element cycles in soil systems. Notably, Ncs can act as effective carriers for other pollutants and contribute to environmental pollution by spreading pathogens, nutrients, heavy metals, and organic contaminants to adjacent water bodies or groundwater. Finally, the key knowledge gaps are highlighted to better predict their potential risks, and important new directions include exploring the geochemical process and mechanism of Ncs's formation; elucidating the transformation, transport, and ultimate fate of Ncs, and their long-term effect on contaminants, organisms, and elemental cycling; and identifying the impact on the growth and quality of important crops, evaluating its dominant effect on agro-ecosystems in the soil environment.

Biotransformation of Chlorpyrifos Shewanella oneidensis MR-1 in the Presence of Goethite: Experimental Optimization and Degradation Products

In this study, the degradation system of Shewanella oneidensis MR-1 and goethite was constructed with chlorpyrifos as the target contaminant. The effects of initial pH, contaminant concentration, and temperature on the removal rate of chlorpyrifos during the degradation process were investigated. The experimental conditions were optimized by response surface methodology with a Box-Behnken design (BBD). The results show that the removal rate of chlorpyrifos is 75.71% at pH = 6.86, an initial concentration of 19.18 mg·L-1, and a temperature of 30.71 °C. LC-MS/MS analyses showed that the degradation products were C4H11O3PS, C7H7Cl3NO4P, C9H11Cl2NO3PS, C7H7Cl3NO3PS, C9H11Cl3NO4P, C4H11O2PS, and C5H2Cl3NO. Presumably, the degradation pathways involved are: enzymatic degradation, hydrolysis, dealkylation, desulfur hydrolysis, and dechlorination. The findings of this study demonstrate the efficacy of the goethite/S. oneidensis MR-1 complex system in the removal of chlorpyrifos from water. Consequently, this research contributes to the establishment of a theoretical framework for the microbial remediation of organophosphorus pesticides in aqueous environments.

Goethite adaptation prompts alterations in antibiotic susceptibility and suppresses development of antibiotic resistance in bacteria

Understanding the impact of environmental factors on antibiotic sensitivity and the emergence of antibiotic resistance in microorganism is crucial for antibiotics management and environmental risk assessment. Natural materials, like mineral particles, are prevalent in aquatic and terrestrial ecosystems. However, it remains unclear how microorganism adapt to the physical stress of mineral particles and whether this adaptation influences antibiotic sensitivity and the evolution of antibiotic resistance. In this study, the model bacterium Escherichia coli (E. coli) was exposed to the mineral particle goethite for 30 generations. Adaptive morphogenesis, including an increase in the fraction of spherical bacteria, variations in bacterial mobility, a slightly increased cell membrane thickness, and genome-wide changes in the transcriptomic profile, were observed in adapted E. coli samples to counteract the stress. Moreover, the goethite adapted E. coli showed increased susceptibility to antibiotics including amoxicillin and tetracycline, and decreased susceptibility to kanamycin compared to its ancestral counterparts. These alterations in antibiotic susceptibility in the adapted E. coli were not heritable, as evidenced by the gradual recovery of antibiotic tolerance in cells with the cessation of goethite exposure. Transcriptomic data and a series of experiments suggested that these changes may be associated with variations in cell membrane property and iron metabolism. In addition, the evolution of antibiotic resistance in adapted cells occurred at a slower rate compared to their ancestral counterparts. For instance, E. coli adapted to goethite at a concentration of 1 mg/mL did not acquire antibiotic resistance even after 13 generations, probably due to its poor biofilm-formation capacity. Our findings underscore the occurrence of microbial adaptation to goethite, which influenced antibiotic sensitivity and decelerated the development of resistance in microorganisms. This insight contributes to our comprehension of the natural dynamics surrounding the evolution of antibiotic resistance and opens new perspectives for addressing this issue through nanotechnology-based approaches.

The inhibitory mechanism of natural soil colloids on the biodegradation of polychlorinated biphenyls by a degrading bacterium

In spite of extensive studies of soil model components, the role of natural soil colloids in the biodegradation of organic pollutants remain poorly understood. Accordingly, the present study selected Mollisol colloids (MCs) and Ultisol colloids (UCs) to investigate their effects on the biodegradation of 3, 3', 4, 4'-tetrachlorobiphenyl (PCB77) by Bradyrhizobium diazoefficiens USDA 110. Results demonstrated that both natural soil colloids significantly decreased the biodegradation of PCB77, which partly resulted from the significant decrease in the bioaccessibility of PCB77. Furthermore, the activity of Bradyrhizobium diazoefficiens USDA 110 was remarkably inhibited under the exposure to the two types of soil colloids, which was mainly ascribed to the inhibition of cell reproduction but not the lethal effect of reactive oxygen species. The calculated results from Ex-DLVO theory further indicated that the repulsion between UCs and biodegrading bacteria retarded the effective contact of cells with adsorbed PCB77 from UCs, resulting in the decline of the rate of cell reproduction. In general, the inhibition of MCs was limited to PCB77 bioaccessibility, whereas the negative effect of UCs was controlled by PCB77 bioaccessibility and the effective contact of cells with colloids. This study could provide implication for the enhancement of microbial remediation in contaminated soil.

Remediation of organophosphorus pesticide polluted soil using persulfate oxidation activated by microwave

Contaminated sites from pesticide industry have attracted global concern due to the characteristics of organic pollution with high concentrations and complete loss of habitat conditions. Remediation of organophosphorus pesticide polluted soil using microwave-activated persulfate (MW/PS) oxidation was investigated in this study, with parathion as the representative pesticide. Approximately 90 % of parathion was degraded after 90 min of MW/PS oxidation treatment, which was superior to those by single PS or MW treatment. Relatively greater performances for parathion degradation were obtained in a relatively larger PS dosage, higher microwave temperature, and lower organic matter content. Appropriate soil moisture favored parathion degradation in soil. SO₄^-, OH, O₂^-, and ¹O₂ generated in the MW/PS system all contributed to parathion degradation. Multiple spectroscopy analyses indicated that PO and PS bonds in parathion were destroyed after MW/PS oxidation, accompanied by generation of hydroxylated and carbonylated byproducts. The soil safety after parathion degradation was assessed via model prediction. Furthermore, MW/PS oxidation also exhibited great performance for degradation of other organophosphorus pesticides, including ethion, phorate, and terbufos.

Aggregation kinetics of binary systems containing kaolinite and Pseudomonas putida induced by different 1:1 electrolytes: specific ion effects

Background

The interactions between colloidal particles in the binary systems or mixture colloids containing clay minerals and bacteria have important influences on formations and stabilities of soil aggregates, transportations of soil water, as well as biological activities of microorganisms. How the interfacial reaction of metal ions affects their interaction therefore becomes an important scientific issue.

Methods

Dynamic light scattering studies on the aggregation kinetics of mixture colloids containing kaolinite and Pseudomonas putida (P. putida) were conducted in this study.

Results

Aggregation could be observed between kaolinite and kaolinite, between kaolinite and P. putida when P. putida content was less than 33.3%. Additionally, aggregation rates decreased with increasing P. putida content. The critical coagulation concentrations and activation energies indicated that there were strong specific ion effects on the aggregation of mixture colloids. Most importantly, the activation energy increased sharply with increasing P. putida content, which might result from the lower Hamaker constant of P. putida compared with that of kaolinite.

Contributions

(1) Strong specific ion effects on mixture colloids aggregation of kaolinite-P. putida were observed; (2) the aggregation behavior of mixture colloids was determined by the average effects of mixture colloids, rather than the specific component. This finding provides an important methodological guide for further studies on the colloidal aggregation behavior of mixture systems with organic and inorganic materials.

Accelerated Biodegradation of the Agrochemical Ametoctradin by Soil-Derived Microbial Consortia

Pesticide-resistant plant pathogens are an increasing threat to the global food supply and have generated a need for novel, efficacious agrochemicals. The current regulatory process for approving new agrochemicals is a tedious but necessary process. One way to accelerate the safety evaluation process is to utilize in vitro systems to demonstrate pesticide degradation by soil microbes prior to ex vivo soil evaluations. This approach may have the capability to generate metabolic profiles free of inhibitory substances, such as humic acids, commonly present in ex vivo soil systems. In this study, we used a packed-bed microbial bioreactor to assess the role of the natural soil microbial community during biodegradation of the triazolopyrimidine fungicide, ametoctradin. Metabolite profiles produced during in vitro ametoctradin degradation were similar to the metabolite profiles obtained during environmental fate studies and demonstrated the degradation of 81% of the parent compound in 72 h compared to a half-life of 2 weeks when ametoctradin was left in the soil. The microbial communities of four different soil locations and the bioreactor microbiome were compared using high throughput sequencing. It was found that biodegradation of ametoctradin in both ex vivo soils and in vitro in the bioreactor correlated with an increase in the relative abundance of Burkholderiales, well characterized microbial degraders of xenobiotic compounds.

Iron mineral-humic acid complex enhanced Cr(VI) reduction by Shewanella oneidensis MR-1

Microorganisms, iron minerals, and humic acid are widely common in the soil and water environment and closely interact within environmental processes. In this study, the Cr(VI) removal by Shewanella oneidensis MR-1 (S. oneidensis) was examined in the presence of goethite and humic acid (HA) to mimic the real environment situation. Scanning electron microscopy (SEM) combined with energy disperse spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR) technologies were used to probe the Cr(VI) reduction mechanism. Our results showed that S. oneidensis alone could reduce 65% of 1.0 mM Cr(VI) after 8 h of the reduction process. Meanwhile, Cr(VI) reduction rate was declined to 56% in the presence of goethite or humic acid. Contrary, the Cr(VI) reduction rate was mightily increased to 79% by the ternary complex of S. oneidensis-goethite-HA where reduced humic acid (HA_red) acted as electron shuttles and diminished the bacterial adhesion to the goethite surface thereby enhanced electron transfer and increased the extent of Cr(VI) reduction by 1.3 fold. XPS analysis indicated that Cr(VI) was reduced to Cr(III), and the final yields were Cr(OH)₃ and Cr₂O₃ precipitated on the surface of bacterial cells. S. oneidensis could also reduce Fe(III) in goethite to Fe(II), which in turn reduced Cr(VI). These results suggested that iron mineral-humic acid complex could enhance the microbial reduction of Cr(VI) and revealed the promotion role of HA in the Cr(VI) bioreduction process. This study affords inclusive insights on the Cr(VI) reduction kinetics and mechanisms in the most complicated systems.

Structural characteristics of humic-like acid from microbial utilization of lignin involving different mineral types

This paper determines the impact of two clay minerals (kaolinite and montmorillonite) and three oxides (goethite, δ-MnO₂, and bayerite) on the elemental composition and FTIR spectra of humic-like acid (HLA) extracted from microbial-mineral residue formed from the microbial utilization of lignin in liquid shake flask cultivation. Goethite, bayerite, and δ-MnO₂ showed higher enrichment capabilities of C and O + S in the HLA than kaolinite and montmorillonite. Goethite showed the highest retention of organic C, followed by bayerite, but kaolinite exhibited the least exchangeability. Kaolinite and montmorillonite enhanced microbial consumption of N, resulting in the absence of N in HLA. A few aliphatic fractions were preferentially gathered on the surfaces of kaolinite and montmorillonite, making the H/C ratios of HLA from the clay mineral treatments higher than those of HLA from the oxide treatments. δ-MnO₂ was considered the most effective catalyst for abiotic humification, and goethite and bayerite ranked second and third in this regard. This trend was proportional to their specific surface areas (SSAs). However, comparing the effects of different treatments on the promotion of HLA condensation by relying solely on the SSA of minerals was not sufficient, and other influencing mechanisms had to be considered as well. Additionally, Si-O-Al and Si-O of kaolinite participated in HLA formation, and Si-OH, Si-O, and Si-O-Al of montmorillonite also contributed to this biological process. Fe-O and phenolic -OH of goethite, Mn-O of δ-MnO₂, and Al-O of bayerite were all involved in HLA formation through ligand exchange and cation bridges. Lignin was better protected from microbial decomposition by the kaolinite, bayerite, and δ-MnO₂ treatments, which caused lignin-like humus (HS) formation. Under the treatments of δ-MnO₂, goethite, and bayerite, HLA showed a greater degree of condensation compared to HLA precipitated by kaolinite and montmorillonite. Contributions from Si-O, and Si-O-Al of clay minerals, and Fe-O, Mn-O, and Al-O of oxides were the mechanisms by which minerals catalyzed the formation of HS from lignin.