Aerobic Environment Research Articles

Tracing sulfate sources and transformations of surface water using multiple isotopes in a mining-rural-urban agglomeration area

Rapid urbanization and mining activities are exacerbating sulfate (SO42-) pollution in surface water, and the information on its sources and transformations is crucial for understanding the sulphur cycle in mining areas. In this study, the SO42- in the surface water of Huaibei mining area were monitored and the main sources of pollution and biogeochemical processes were identified using stable isotopes (δD, δ18O-H2O, δ34S-SO42- and δ18O-SO42-) and water chemistry. The results demonstrated the SO42- content in the Huihe River and Linhuan subsidence water area (SWA) is higher than that in other rivers and SWAs, which exceeded the environmental quality standard of surface water. The SO42- content of different rivers and SWAs showed seasonal differences, and the dry season was higher than the wet season. In addition, the SO42- in Tuohe River and Suihe River is primarily caused by urban sewage and agriculture activities, while in Zhonghu and Shuoxihu SWA is mainly contributed by natural evaporate dissolution. Notably, the input of SO42- in the Huihe River and Linhuan SWA caused by mining activities cannot be disregarded. The aerobic environment and isotopic fractionation of surface water indicate that sulfide oxidation is not the major cause of SO42- formation. This work has revealed the multiple sources and transformation mechanisms of SO42-, and provided a reference for the development of comprehensive management and effective remediation strategies of SO42- contamination in surface water around mining areas.

Variovorax durovernensis sp. nov., a novel species isolated from an infected prosthetic aortic graft in a human.

A novel bacterial strain, GSTT-20T was isolated from an infected, prosthetic endovascular graft explanted from a shepherd in London, United Kingdom. This strain was an aerobic, catalase-positive, oxidase-negative, Gram-stain-negative, motile, curved rod. It grew on blood agar, chocolate agar and MacConkey agar incubated at 37 °C in an aerobic environment after 48 h, appearing as yellow, mucoid colonies. Analysis of the complete 16S rRNA gene sequence showed closest similarity to Variovorax paradoxus with 99.6 % identity and Variovorax boronicumulans with 99.5 % identity. Phylogenetic analysis of the 16S rRNA gene sequence and phylogenomic analysis of single nucleotide polymorphisms within 1530 core genes showed GSTT-20T forms a distinct lineage in the genus Variovorax of the family Comamonadaceae. In silico DNA-DNA hybridization assays against GSTT-20T were estimated at 32.1 % for V. boronicumulans and 31.9 % for V. paradoxus. Genome similarity based on average nucleotide identity was 87.50 % when comparing GSTT-20T to V. paradoxus. Based on these results, the strain represented a novel species for which the name Variovorax durovernensis sp. nov. was proposed. The type strain is GSTT-20T (NCTC 14621T=CECT 30390T).

Detection of antimicrobial susceptibility and virulence factors for some bacterial species caused urinary tract infection among type 1 and type 2 diabetes mellitus patients

Abstract Background: Diabetes mellitus (DM), is a metabolic illness caused by a deficiency in insulin production, action, or both, it is characterized by hyperglycemia and disruptions of the metabolism of carbohydrates, proteins, and fats. Urinary tracts infections (UTIs) are conditions when one or more urinary tract structures become contaminated after germs get past the body’s robust natural defenses. The most prevalent illness, UTIs can happen at any moment during a person’s lifetime. UTIs and DM have been linked for many years. Owing to a shift in the host defense mechanism, a micro-vascular illness in the kidney, and the existence of diabetic cystopathy, the incidence of UTIs is significant in DM. Urinary colonization by bacteria is made possible by high glucose concentrations in urine flow. Objective: Detection of antimicrobial susceptibility and virulence factors among bacteria causing UTIs isolated from type 1 and type 2 diabetic patients. Materials and Methods: Between April and July 2022, 178 patients with diabetes who had signs of a UTI had their urine samples taken. Midstream urine samples from DM patients were inoculated into blood agar and MacConkey agar using a calibrated loop (0.001 mL). For 24 h, cultures were incubated at 37°C in an aerobic environment. To determine whether there had been any considerable growth, colonies were counted. Diagnostic microorganisms were tested for their susceptibility to various antibiotics, and virulence factors were found. Results: Significant bacteriuria was observed in 28 of 69 (40.5%) and 52 of 109 (47.7%) urine samples cultured from patients with type 1 and 2 diabetes, respectively. Sensitivity to isolates which isolated from patients with type 1 and type 2 diabetes was highest for meropenem as 90% and 100%, respectively. With regard to virulence factor, it was investigated of biofilm formation, hemolysin production, protease production, urease production, and β-lactamase production. The highest ratio of these factors production in bacteria which isolated from patients with type 1 diabetes was β-lactamase (75.8%). As for patients with type 2 diabetes, the highest ratio was for biofilm formation (79.0%). Conclusion: According to this study, common antimicrobials are very resistant to many different drugs. UTIs are more common than previously thought, and type of diabetes was discovered to be one of the key contributing factors. We found an association between virulence factors of pathogens and type of diabetes.

Contrasting response strategies of sulfate-reducing bacteria in a microbial consortium to As3+ stress under anaerobic and aerobic environments

The sulfate-reducing efficiency of sulfate-reducing bacteria (SRB) is strongly influenced by the presence of oxygen, but little is known about the oxygen tolerance mechanism of SRB and the effect of oxygen on the metalliferous immobilization by SRB. The performance evaluation, identification of bioprecipitates, and microbial and metabolic process analyses were used here to investigate the As3+ immobilization mechanisms and survival strategies of the SRB1 consortium under different oxygen-containing environments. Results indicated that the sulfate reduction efficiency was significantly decreased under aerobic (47.37%) compared with anaerobic conditions (66.72%). SEM analysis showed that under anaerobic and aerobic conditions, the morphologies of mineral particles were different, whereas XRD and XPS analyses showed that the most of As3+ bioprecipitates under both conditions were arsenic minerals such as AsS and As4S4. The abundances of Clostridium_sensu_stricto_1, Desulfovibrio, and Thiomonas anaerobic bacteria were significantly higher under anaerobic than aerobic conditions, whereas the aerobic Pseudomonas showed an opposite trend. Network analysis revealed that Desulfovibrio was positively correlated with Pseudomonas. Metabolic process analysis confirmed that under aerobic conditions the SRB1 consortium generated additional extracellular polymeric substances (rich in functionalities such as Fe-O, SO, CO, and -OH) and the anti-oxidative enzyme superoxide dismutase to resist As3+ stress and oxygen toxicity. New insights are provided here into the oxygen tolerance and detoxification mechanism of SRB and provide a basis for the future remediation of heavy metal(loid)-contaminated environments.

Control of Corrosion Rate of Metal Alloys: SS 304 And SS 201 Using Phosphate Inhibitor in Nacl 3.5%

Corrosion is metal damage caused by electrochemical reactions with its environment. This environment can be water, air, gas, acid solution, salt solution, and others. Metals are highly active in producing an oxide layer on the metal surface under the influence of an aerobic environment. Metal corrosion is a process where the action of the surrounding media damages metal materials by the introduction of corrosion ions. This study aims to determine the best conditions for phosphate in controlling the rate of corrosion and Knowing the inhibition of phosphate on controlling the rate of corrosion. The materials used were stainless steel 201, stainless steel 304, and phosphate as an inhibitor. Meanwhile the solution NaCl 3.5% as a corrosive media environment and distilled water. Based on this research, the best phosphate concentration in reducing the corrosion rate of stainless steel 201 and 304 is 100 ppm with a reduction in the corrosion rate of stainless steel 201 of 0.022312 mpy with an inhibition percentage of 89.68%, and a reduction in the corrosion rate of stainless steel 304 by 0.045694 mpy with the percentage of inhibition is 94.027%. The corrosion rate of 304 stainless steel is lower than that of 201 stainless steel caused by differences in the Cr element composition of each metal. Stainless steel 304 contains 18.24% Cr while stainless steel 201 contains 13.00% Cr. The lower the Cr content in stainless steel, the stainless steel will be more susceptible to corrosion.

Siltation of check dams alters microbial communities and thus limits organic carbon mineralization

Check dam interception in the Loess Plateau leads to a buildup of silt-based deep soil reserves. These deep soils tend to be high in organic carbon (C), and could dramatically impact our estimates of terrestrial C storage. Despite a growing interest in the terrestrial C cycle, little work has focused on deep soil organic carbon (SOC) pools. In this study, we observed how soil depth and consequential oxygen concentration may influence the way in which microorganisms act on the SOC mineralization process. We found that the change from aerobic to anaerobic environment led to a decrease in cumulative mineralization from 1.37 mg to 1.06 mg and a significant decrease in mineralization rate, which had a limiting effect on SOC mineralization. The reduction of oxygen concentration (approximating depth) also led to changes in the dominant population of bacteria/fungi. Microorganisms with higher C metabolism capacity in aerobic conditions had higher utilization of C sources than that in anaerobic conditions, and vice versa. The limiting factors affecting the amount of SOC mineralization in aerobic soil were carbohydrate, Rokubacteria and Mortierellomycota, and that in anaerobic soil were Amino acid, Mortierellomycota and Ascomycota. Microorganisms with high C metabolism in anaerobic conditions have a weaker metabolism in aerobic conditions, and vice versa. We further quantified the direct and interactive contribution of each factor to SOC mineralization and found that when the soil was aerobic, the contribution of single factor to SOC mineralization was significantly lower (0.32) than the interactions (0.65). Conversely, when the soil was anaerobic, the contribution of single factor to SOC mineralization was much higher (0.76) than the interactions (0.20). When the soil is in anaerobic condition for a long time, the contribution of single factor will gradually increase and the interactions among factors will gradually weaken, further limiting SOC mineralization. In this study, the mechanism of SOC mineralization based on microbial activity in anaerobic and aerobic environment of check dam was reported for the first time, providing theoretical support for understanding the contribution of check dam construction to SOC pool on the Loess Plateau.

Electrochemiluminescence Properties and Sensing Application of Zn(II)-Metal-Organic Frameworks Constructed by Mixed Ligands of Para Dicarboxylic Acids and 1,10-Phenanthroline.

Four metal-organic frameworks (MOFs) were designed and prepared through a mixed-ligand strategy by controlling the combination of various dicarboxylic acid ligands with invariant center metal and o-phenanthroline heterocyclic ligand. The regulatory effects of ligand electronic band and crystal structure on the electrochemiluminescence (ECL) characteristics of MOFs were verified by experimental results and density functional theory (DFT) calculations. The flexible chain structure of MOF-2 promotes electron transfer between MOF electroactive free radicals and the co-reactant, making it show outstanding ECL characteristics among all of the four MOFs with the luminescence quantum efficiency 8.37 times that of tris(bipyridine)-ruthenium(II) ([Ru(bpy)3]2+). Meanwhile, a new ECL mechanism for MOF luminescent crystal materials with reactive oxygen species in solvents as a co-reactant in the aqueous aerobic environment has been proposed. MOF-2 was selected to construct an ECL sensor for the determination of glucose in human urine samples. This study provides a useful idea for the development and design of new luminescent molecular crystal materials.

Cold tolerance in Campylobacter jejuni and its impact on food safety

Campylobacter jejuni is a major cause of foodborne illnesses worldwide and is primarily transmitted to humans through contaminated poultry meat. To control this pathogen, it is critical to understand its cold tolerance because poultry products are usually distributed in the cold chain. However, there is limited information regarding how this thermotolerant, microaerophilic pathogen can survive in cold and aerobic environments in the poultry cold chain. In this study, we investigated the cold tolerance of C. jejuni by measuring the viability of 90 C. jejuni strains isolated from retail raw chicken at 4 °C under aerobic and microaerobic conditions. Despite the microaerophilic nature of C. jejuni, under aerobic conditions, C. jejuni exhibited higher viability at 4 °C and required an extended inactivation time compared to microaerobic conditions. Some strains were highly tolerant to refrigeration temperatures and exhibited increased survival at 4 °C. These cold-tolerant strains mostly belonged to multilocus sequence typing (MLST) clonal complex (CC)-21 and CC-443, indicating that cold tolerance is associated with the phylogeny of C. jejuni. Notably, cold-tolerant strains had an increased probability of illness and were more likely to cause human infections due to their extended survival on refrigerated chicken meat compared to those sensitive to cold stress. Furthermore, the majority of cold-tolerant strains exhibited elevated aerotolerance, indicating that cold tolerance is related to aerotolerance. These findings suggest that refrigeration of chicken meat under aerobic conditions may not be effective at controlling C. jejuni and that cold-tolerant C. jejuni can pose an increased risk to food safety.

Use of Lactobacillus Bacteria to Degrade Oil and Grease in Restaurant Wastewater

Restaurant wastewater poses a significant environmental challenge, especially concerning the removal of oil and grease, which is known to be highly persistent. To tackle this issue, the research utilized a Lactobacillus bacteria consortium to effectively degrade oil and grease present in the wastewater. The Lactobacillus bacteria consortium was applied in an aerobic environment within the Grease Trap, while various treatment conditions, such as hydraulic retention time (HRT) and aeration rate, were evaluated to determine the optimal settings for the SBR. By employing this combined pre-treatment and SBR approach, distinct aerobic and anaerobic conditions were created, leading to significant removal of pollutant parameters by microorganisms. Remarkably, the study's findings demonstrated that at a 24-hour retention time and a 14 L/minute aeration rate, the Lactobacillus bacteria consortium achieved an impressive 97.42% removal of oil and grease, compared to only 84.54% removal by the Grease Trap without bacteria. The pretreatment of the Lactobacillus bacteria consortium led to even higher reductions in other pollutant parameters. By harnessing the power of the Lactobacillus bacteria consortium and employing the SBR in combination with pre-treatment, this approach holds great potential for addressing the persistent challenge of oil and grease removal in restaurant wastewater and improving overall water quality.

Cationic Conjugated Oligomers for Efficient and Rapid Antibacterial Photodynamic Therapy via Both Type I and Type II Pathways

Comprehensive SummaryRecently, photodynamic therapy (PDT) has attracted wide attention due to its less susceptibility to drug resistance, broad‐spectrum biocidal activity and biosafety in normal tissues. However, the traditional photosensitizers (PSs) face the disadvantage of poor therapeutic efficacy due to the requirement of an aerobic environment to generate 1O2 through Type ІI pathway. Herein, we designed and synthesized a novel cationic conjugated oligomer oligo(phenylene vinylene) (OPV) and studied its antibacterial photodynamic activity against both Gram‐negative Escherichia coli (E. coli) and Gram‐positive bacteria methicillin‐resistant Staphylococcus aureus (MRSA). Importantly, the OPV can rapidly produce reactive oxygen species (ROS) through double pathways, Type I and II mechanism under white light irradiation, and efficiently kill E. coli and MRSA at a nanomolar level. The dual type photosensitizing capability makes OPV promising for enhanced PDT to treat pathogens and tumors in complex environments.

Preparation of silicon-nitride ceramic fibers with hafnium compounds loaded on the surface and the high temperature properties

The surface and core are composed of heterogeneous fiber materials that are endowed with excellent properties due to the unique structure. In this work, polysiloxane (PSZ) was used as the ceramic precursor and hafnium carbide (HfC) was used as the hafnium source, and Si–N–C–O-Hf hybridized ceramic fibers were obtained using electrostatic spinning and pyrolysis. After the primary fibers were pyrolyzed at 1400 °C, hemispherical particles were found on the surface of the ceramic fibers. And the average fiber diameters were around 3 μm. Thermogravimetric analysis (TGA) showed that the mass of the cured fibers decreased to 67 % below 1650 °C in an argon atmosphere. The mass of the ceramic fibers remained almost unchanged in the high temperature aerobic environment. Meanwhile, the thermal conductivity of the specimens has remained relatively low. Analytical tests confirmed that the hafnium-containing hemispherical protective layer gave the specimens excellent thermal stability, oxidation resistance, and high temperature insulation. In addition, the excellent mechanical properties make it suitable for a wide range of applications. The optimized high-temperature performance and mechanical properties indicate that metal-hybridized silicon-based ceramic fibers herein are suitable for ultra-high-temperature environments.

Inducing root redundant development to release oxygen: An efficient natural oxygenation approach for subsurface flow constructed wetland

Dissolved oxygen (DO) is a limiting factor affecting the purification efficiency of subsurface flow (SSF) constructed wetlands (CWs). To clarify the causes of oxygen environments and the response characteristics of plant oxygen release (POR) in SSF CWs, this study set three oxygen source treatments by limiting atmospheric reaeration (AR) and influent oxygen (IO) and compared the differences in plant physiological metabolism, DO distribution characteristics, and the purification effect of the SSF CWs at different depths. The results showed that limiting exogenous oxygen stimulated root redundancy of the wetland plants. The root volume and proportion of fibrous roots of the wetland plants increased significantly (p < 0.05). When only the POR existed, the root zone DO increased significantly to 2.05–4.37 mg/L (p < 0.05), and was positively correlated with the TN and TP removal rates (p < 0.05). Additionally, in the presence of POR only, the average removal rates of TN and TP in the top layer were 86.5% and 76.9%, respectively. The proportion of fibrous roots, root zone DO, and root-shoot ratio were key factors promoting the purification effect of the SSF CWs under limited exogenous oxygen sources. Enhancing POR by inducing root redundancy enhanced nitrification (hao, pmoABC-amoABC), plant absorption, and assimilation-related functional genes (nrtABC, nifKDH), and enriched nitrogen and phosphorus removal bacteria, such as Flavobacterium and Zoogloea. This consequently improved pollutant removal efficiency. Inducing root redundancy to strengthen POR produced an aerobic environment in the SSF CWs. This ensures the efficient and stable operation of the SSF CW and is an effective approach for natural oxygenation.

Mechanisms for thallium(I) adsorption by zinc sulfide minerals under aerobic and anaerobic conditions

The highly toxic heavy metal thallium is widely distributed in sulfide ores and released into the environment by sulfide mining. However, the interface between the sulfide minerals and Tl(I) is unclear. In this study, the capacity for adsorption of thallium(I) by a common sulfide mineral (zinc sulfide) was investigated in aerobic and anaerobic environments, which revealed three mechanisms for adsorption on the ZnS surface (surface complexation, electrostatic action and oxidation promotion). Batch experiments indicated that the Tl(I) adsorption capacity of ZnS in an aerobic environment was approximately 9.3% higher than that in an anaerobic environment and was positively correlated with the pH. The adsorption kinetic data showed good fits with the pseudosecond-order model and the Freundlich isotherm model. The Tl(I) adsorption mechanism varied in different oxidative and pH environments. XPS, FTIR, and EDS results implied that complexation with surface hydroxyl groups was involved in the adsorption process. pH experiments and zeta analyses suggested that electrostatic attraction was also involved. Surface complexation and electrostatic attraction were the dominant mechanisms at pH values above 6. Furthermore, oxidative dissolution of ZnS and hydrolysis of Zn2+ enhanced the complexation with hydroxyl groups on the mineral surface and facilitated Tl adsorption. In this study, this interface mechanism provided new insights into thallium migration in sulfurized mineral environments in aerobic and anaerobic transition regions.

Enzyme-functionalized alginate microparticles enable anaerobic culture under ambient oxygen.

Methods for culturing oxygen-sensitive cells and organisms under anaerobic conditions are vital to biotechnology research. Here, we report a biomaterial-based platform for anaerobic culture that consists of glucose oxidase (GOX) functionalized alginate microparticles (ALG-GOX), which are designed to deplete dissolved [O2 ] through enzymatic activity. ALG-GOX microparticles were synthesized via a water-in-oil emulsion and had a size of 132.0 ± 51.4 µm. Despite having a low storage modulus, the microparticles remained stable under aqueous conditions due to covalent crosslinking through amide bonds. Enzyme activity was tunable based on the loaded GOX concentration, with a maximum activity of 3.6 ± 0.3 units/mg of microparticles being achieved at an initial loading concentration of 5 mg/mL of GOX in alginate precursor solution. High enzyme activity in ALG-GOX microparticles resulted in rapid oxygen depletion, producing a suitable environment for anaerobic culture. Microparticles loaded with both GOX and catalase (ALG-GOX-CAT) to reduce H2 O2 buildup exhibited sustained activity for potential long-term anaerobic culture. ALG-GOX-CAT microparticles were highly effective for the anaerobic culture of Bacteroides thetaiotaomicron, with 10 mg/mL of ALG-GOX-CAT microparticles supporting the same level of growth in an aerobic environment compared to an anaerobic chamber after 16 h (8.70 ± 0.96 and 10.03 ± 1.03 million CFU, respectively; N.S. p = 0.07). These microparticles could be a valuable tool for research and development in biotechnology.

Proto-dolomite spherulites with heterogeneous interior precipitated in brackish water cultivation of freshwater cyanobacterium Leptolyngbya boryana

Primary dolomite is believed to be formed through cyanobacterial calcification, yet the details and mechanisms of this process are not fully understood. In this study, a freshwater filamentous cyanobacterium, Leptolyngbya boryana, was cultured and domesticated in artificial freshwater and brackish solutions with various Mg/Ca ratios. The hydrochemistry, the extracellular polymeric substance (EPS) composition, and precipitate mineralogy in the medium were monitored. The results showed that the L. boryana induced proto-dolomite precipitation in brackish medium with salinity of 1.5 % and Mg/Ca ratio of 5. The proto-dolomite in this study has a “double spherical” appearance and a hollow core, which may have originally been filled by the complex composed of EPS and amorphous CaMg carbonate. With regard to elemental composition, the cyanobacterially-induced proto-dolomite is rich in calcium inside and magnesium-rich on the surface, and cyanobacterial organic matter is sealed inside the particles during spherulite growth. In this study, the accelerators for Mg2+ to enter the carbonate lattice mainly include extracellular acidic amino acids and polysaccharides. The changes of these promoters among different cultures were related to the growth state of cyanobacteria under salinity stress. The polysaccharides concentration has a significant increasing in the dolomite-precipitating medium, indicating that it may be the main promoter of proto-dolomite precipitation and significantly increases the amount of Mg2+ precipitation. At the meantime, the amount of precipitated Ca2+ was suppressed by increasing salinity and Mg2+, thus leading to the precipitation of proto-dolomite in this shifting process. This study can potentially provide a reference for explaining the dolomite (proto-dolomite) precipitation in aerobic brackish environment where cyanobacteria thrive.

Petrofabric and geochemical constraints on the origin of Liuyang chrysanthemum stone, South China

Chrysanthemum stone refers to a radial and chrysanthemum–like mineral aggregate. Liuyang chrysanthemum stone, distributed in the carbonate of the Permian Chihsian Formation in South China, has become a rare natural art treasure due to its unique radial shape. The lack of effective constraints on the petrography and geochemistry of the chrysanthemum stone in Liuyang restricts the understanding of its origin. Hence, petrography analysis and Raman microprobe spectroscopy were used to study the mineral compositions and textural characteristics of the Liuyang chrysanthemum. Element and isotope geochemistry studies were conducted to discuss the sedimentary environment, material source, and formation mechanism. The Liuyang chrysanthemum stone was formed in the period of aragonite sea, and developed in dark gray limestone as a white radial mineral aggregate. The primary mineral is celestite, a minor amount of which was filled with and metasomatized by calcite. Trace element characteristics (δCe = 0.46–0.70, V/Cr = 1.28–1.51, Ni/Co = 2.14–4.89, Sr/Ba = 14.42–45.17) and carbon and oxygen isotopic compositions (δ13CV–PDB = 3.0 ‰–3.8 ‰, δ18OV–PDB = 5.2 ‰–4.8 ‰) of the host rocks indicate an aerobic marine sedimentary environment. The significant difference in sulfur isotopic compositions between the chrysanthemum stone (δ34S = 29.4 to 28.1 ‰) and the host rocks (δ34S = –29.4 to –28.1 ‰) indicates that bacterial sulfate reduction (BSR) and anerobic oxidation of methane (AOM) has occurred. Petrography, trace element and C–O–S isotope geochemistry of the Liuyang chrysanthemum stone had revealed the formation process of the chrysanthemum stone. The organic matter was decomposed by O2 and produced CO2 in the aerobic marine sedimentary environment. With the continuous sedimentation and the oxygen consumption, the early sedimentary carbonate and bioclastic was gradually separated from the relatively aerobic environment. An anoxic sedimentary–diagenetic environment was formed and the BSR occurred, during which SO42– participated in the degradation of organic matter as an electron acceptor. The bacteria preferentially absorbed the light 32SO42– in pore water to produce 32S–rich FeS2 in the host rocks and the heavy SO42– was combined with the Sr2+ released by aragonite dissolved by the accumulated CO2 to precipitate the celestite. HCO3– accumulated during the AOM and the BSR resulted in the replacement of the celestite by the calcite.

Microbiologically influenced corrosion inhibition of two marine structural steels caused by Halomonas titanicae in aerobic environments

Corrosion is a global problem, especially in marine environments. The currently popular corrosion mitigation methods have the drawbacks of being costly, susceptible to environmental limitations, or causing environmental contamination. Microbiologically influenced corrosion inhibition (MICI), as a widespread phenomenon, can provide a new strategy utilizing bacteria to control corrosion. This study investigated the MICI mechanism of Halomonas titanicae on two marine structural steels (EH36-low alloy steel (E-LAS) (with copper) and Q235-carbon steel (Q-CS) (without copper)) in aerobic environments. Results show that the corrosion of E-LAS and Q-CS was both inhibited by H. titanicae in an aerobic enriched seawater. It was found that the aerobic respiration mode of H. titanicae was very different from its anaerobic respiration. The former respiration mode significantly reduced the dissolved oxygen (DO) concentrations in the medium. In addition, the DO levels in the biotic medium immersed with the two steels were similar, but the corrosion inhibition degree of E-LAS (22% drop) caused by H. titanicae was weaker than that of Q-CS (55% drop), indicating that the MICI mechanism of H. titanicae goes beyond simply reducing the DO concentration. The number of sessile cells on E-LAS was only 20% of that on Q-CS due to Cu in E-LAS, which led to a thinner extracellular polymeric substance (EPS) film and a corrosion product film with less Fe(II) content. This reduced the Rf values significantly. Therefore, the EPS and corrosion product films caused by H. titanicae aerobic respiration are also important in the corrosion inhibition process.

Radon exhalation characteristics after pyrolysis of long flame coal

Coal pyrolysis is a important method for classifying and utilizing coal resources and contributes to enhanced comprehensive resource utilization. However, In high-temperature areas such as coal pyrolysis, there is an abnormal phenomenon release of radioactive gas radon, understanding the relationship between temperature and radon exhalation characteristics, as well as the underlying mechanisms, holds great importance for assessing radon pollution in mining areas. After coal undergoes pyrolysis under high temperature conditions, its material composition, pore structure, water content, and other properties have changed. The pyrolysis products in different atmosphere environments have differences, and the characteristics of radon emission are also different. To address this, the present study conducted coal pyrolysis experiments in both aerobic and anaerobic environments, using long flame coal sourced from Yulin, China. The radon release concentration of the pyrolysis products was measured. The research findings indicate that during pyrolysis at elevated temperatures, the ratio of coal mass loss is constantly increasing. High temperatures promote the development of pores and fissures, and significant changes in coal properties at temperature thresholds (300 °C and 500 °C). The specific surface area, pore volume, and fracture ratio all display substantial increases, and the amplitude of change is greater under aerobic conditions. The fractal dimension of total pores and macropores shows continuous growth, while the specific surface area, pore volume, and fracture ratio exhibit a strong negative correlation with the radon emission rate of pyrolysis products. The expansion and penetration of pores and cracks, along with the release of a substantial amount of pyrolysis gas, accelerate the transformation, migration, and exhalation of radon, resulting in a negative correlation between the heat treatment temperature and the radon release rate of pyrolysis products. Under aerobic conditions, the radon release rate of pyrolysis products decreases more significantly.

Enhanced nitrogen removal from micro-polluted water by Fe (II)/Fe (III) cycling under intermittent aeration

The potential of iron-carbon materials (FeC) as inorganic electron donors for aerobic denitrification of micro-polluted source water was explored. For this purpose, a raw water denitrification experiment was conducted using FeC under intermittent aeration condition. Then, magnetite was added as a biological carrier to construct another system, FeC and magnetite intermittent aeration reaction system, (FCMI). The findings revealed that FCMI notably removed the pollutants with the removal efficiencies of nitrate, total nitrogen, total phosphorus, and chemical oxygen demand reaching 95.63%, 88.62%, 90.48%, and 61.46%, respectively. Cycling between aerobic and anaerobic environments facilitated the formation of Fe (II)/Fe (III) cycle within FeC materials. Microbial profiling revealed that Proteobacteria and Actinobacteria comprised 97.14% of the total abundance in FCMI. Iron-reducing bacteria and aerobic denitrifying bacteria were found to thrive on the surface of magnetite materials. The abundance of enzymes related to denitrification under intermittent aeration exceeded those under continuous aeration levels by 8–19%. This study verifies the ability of iron electrons to cycle under intermittent aeration condition and proposes a novel strategy for in-situ denitrification of micro-polluted source water.

Competitive and substrate limited environments drive metabolic heterogeneity for comammox Nitrospira

Nitrospira has been revealed as a high versatile genus. Although previously considered only responsible for the conversion of nitrite to nitrate, now we know that Nitrospira can perform complete ammonia oxidation to nitrate too (comammox). Comammox activity was firstly reported as dominant in extremely limited oxygen environments, where anaerobic ammonia oxidation was also occurring (anammox). To explain the comammox selection, we developed an Individual-based Model able to describe Nitrospira and anammox growth in suspended flocs assembled in a dynamic nitrogen and oxygen-limiting environment. All known and hypothesized nitrogen transformations of Nitrospira were considered: ammonia and nitrite oxidation, comammox, nitrate-reducing ammonia oxidation, and anaerobic nitrite-reducing ammonia oxidation. Through bioenergetics analysis, the growth yield associated to each activity was estimated. The other kinetic parameters necessary to describe growth were calibrated according to the reported literature values. Our modeling results suggest that even extremely low oxygen concentrations (~1.0 µM) allow for a proportional growth of anammox versus Nitrospira similar to the one experimentally observed. The strong oxygen limitation was followed by a limitation of ammonia and nitrite, because anammox, without strong competitors, were able to grow faster than Nitrospira depleting the environment in nitrogen. These substrate limitations created an extremely competitive environment that proved to be decisive in the community assembly of Nitrospira and anammox. Additionally, a diversity of metabolic activities for Nitrospira was observed in all tested conditions, which in turn, explained the transient nitrite accumulation observed in aerobic environments with higher ammonia availability.