Elastin-like polypeptide-functionalized nanobody for column-free immunoaffinity purification of aflatoxin B1.

A column-free immunoaffinity purification (CFIP) technique for sample preparation of aflatoxin B1 (AFB1) was developed using an AFB1-specific nanobody (named G8) and an elastin-like polypeptide (ELP). The reversible phase transition between liquid and solid in response to temperature changes was exhibited by the ELP which was derived from human elastin. The G8 was tagged with ELPs of various lengths (20, 40, 60, and 80 repeat units) at the C-terminus using recursive directional ligation (RDL). Coding sequences were then subcloned into pET30a at the multiple cloning sites. Bioactive recombinant proteins were produced by expressing them as inclusion bodies in Escherichia coli BL21 (DE3), then dissolved and refolded. Analysis by indirect competitive enzyme-linked immunosorbent assay (icELISA) and transition temperature (Tt) measurement confirmed that the refolded G8-ELPs preserved the ability to recognize AFB1 as well as phase transition when the temperature rose above Tt. To establish the optimal conditions for cleaning AFB1, the effects of various parameters on recovery were investigated. The recovery in ELISA tests was 95 ± 3.67% under the optimized CFIP workflow. Furthermore, the CFIP-prepared samples were applied for high-performance liquid chromatography (HPLC) detection. The recovery in the CFIP-HPLC test ranged from 54 ± 1.86% to 98 ± 3.58% for maize, rice, soy sauce, and vegetable oil samples. To the best of our knowledge, this is the first report combining the function of both nanobody and ELP to develop a cleanup technique for small molecules in a complex matrix. The CFIP for the sample pretreatment was easy to use and inexpensive. In contrast to conventional immunosensitivity materials, the reagent utilized in the CFIP was entirely biosynthesized without any chemical coupling reactions. This suggests that the nanobody-ELP may serve as a useful dual-functional reagent for the development of sample cleaning or purification methods.

Enhancing the bioreduction and interaction of arsenic and iron by thiosulfate in groundwater.

Thiosulfate influences the bioreduction and migration transformation of arsenic (As) and iron (Fe) in groundwater environments. The aim of this study was to investigate the impact of microbially-mediated sulfur cycling on the bioreduction and interaction of As and Fe. Microcosm experiments were conducted, including bioreduction of thiosulfate, As(V), and Fe(III) by Citrobacter sp. JH012-1, as well as the influence of thiosulfate input at different initial arsenate concentrations on the bioreduction of As(V) and Fe(III). The results demonstrate that Citrobacter sp. JH012-1 exhibited strong reduction capabilities for thiosulfate, As(V), and Fe(III). Improving thiosulfate level promoted the bioreduction of Fe(III) and As(V). When 0, 0.1, 0.5, and 1 mM thiosulfate were added, Fe(III) was completely reduced within 9 days, 3 days, 1 day, and 0.5 days, simultaneously, 72.8%, 82.2%, 85.5%, and 90.0% of As(V) were reduced, respectively. The products of As(III) binding with sulfide are controlled by the ratio of As-S. When the initial arsenate concentration was 0.025 mM, the addition of thiosulfate resulted in the accumulation of soluble thioarsenite. However, when the initial arsenate level increased to 1 mM, precipitates of orpiment or realgar were formed. In the presence of both arsenic and iron, As(V) significantly inhibits the bioreduction of Fe(III). Under the concentrations of 0, 0.025, and 1 mM As(V), the reduction rates of Fe(III) were 100%, 91%, and 83%, respectively. In this scenario, the sulfide produced by thiosulfate reduction tends to bind with Fe(II) rather than As(III). Therefore, the competition of arsenic-iron and thiosulfate concentration should be considered to study the impact of thiosulfate on arsenic and iron migration and transformation in groundwater.

A conversion CRT strategy combined with AVJA may be a perspective alternative for heart failure patients with persistent atrial fibrillation.

Heart failure (HF) combined with persistent atrial fibrillation (AF) often coexist and may promote the pathological conditions of cardiac dysfunction, leading to poor prognosis. Cardiac resynchronization therapy (CRT) combined with atrioventricular junction ablation (AVJA) is a highly effective treatment for HF patients with underlying AF who either have failed or are not suitable for catheter ablation. The CRT-AVJA combination therapy can improve clinical outcomes in HF patients. Currently, clinical CRT methods are categorized into biventricular pacing (BVP) - based and conduction system pacing (CSP) - based methods. These procedures have inherent advantages and disadvantages, in addition to their considerable differences in clinical applications. This article aims to review the clinical progress of AVJA combined with different CRT strategies for treating HF patients with persistent AF and propose that conversion CRT strategy (BVP/CSP-CRT) combined with AVJA may be a perspective alternative. Meanwhile, we generalize that 7 categories of HF patients with persistent AF may need to consider the CRT-AVJA combination therapy.

A new strategy of transforming an ACQ compound into an AIE theranostic system for bacterial imaging and photodynamic antibacterial therapy.

An organic chemical with fluorescence quenching properties [aggregation-caused quenching (ACQ)] may often be transformed by adding functional groups that cause aggregation-induced emission (AIE) to its molecular scaffold. Such structural change techniques, however, sometimes require challenging chemical reactions. SF136 is a type of chalcone, and it is an typical ACQ organic compound. In this study, cationic surfactants like hexadecyltrimethylammonium bromide (CTAB) and polyethyleneimine (PEI) were used to convert the ACQ compound SF136 into an AIE compound without adding any AIE structure units. In comparison to SF136, the SF136-CTAB NPS system not only demonstrated improved bacterial fluorescence imaging capabilities, but also increased photodynamic antibacterial activity, which is connected to its improved targeting and reactive oxygen species (ROS) production abilities. It is a promising theranostic substance against bacteria owing to these enhanced qualities. Other ACQ fluorescent compounds may also benefit from using this approach, broadening the scope of their potential applications.

A unique subseafloor microbiosphere in the Mariana Trench driven by episodic sedimentation.

Hadal trenches are characterized by enhanced and infrequent high-rate episodic sedimentation events that likely introduce not only labile organic carbon and key nutrients but also new microbes that significantly alter the subseafloor microbiosphere. Currently, the role of high-rate episodic sedimentation in controlling the composition of the hadal subseafloor microbiosphere is unknown. Here, analyses of carbon isotope composition in a ~ 750 cm long sediment core from the Challenger Deep revealed noncontinuous deposition, with anomalous 14C ages likely caused by seismically driven mass transport and the funneling effect of trench geomorphology. Microbial community composition and diverse enzyme activities in the upper ~ 27 cm differed from those at lower depths, probably due to sudden sediment deposition and differences in redox condition and organic matter availability. At lower depths, microbial population numbers, and composition remained relatively constant, except at some discrete depths with altered enzyme activity and microbial phyla abundance, possibly due to additional sudden sedimentation events of different magnitude. Evidence is provided of a unique role for high-rate episodic sedimentation events in controlling the subsurface microbiosphere in Earth's deepest ocean floor and highlight the need to perform thorough analysis over a large depth range to characterize hadal benthic populations. Such depositional processes are likely crucial in shaping deep-water geochemical environments and thereby the deep subseafloor biosphere. Supplementary Information: The online version contains supplementary material available at 10.1007/s42995-023-00212-y.

Three-dimensional mapping in cardiac implantable electronic device - a feasible and effective alternative to fluoroscopy.

BACKGROUND: During the last decade, three-dimensional mapping technology has substantially aided the development of cardiac implanted electronic devices (CIEDs). This article intends to present an outline of the use and benefits of three-dimensional (3D) mapping systems in CIEDs. RESULT: As an alternative to fluoroscopy, 3D mapping greatly minimizes radiation exposure and eliminates the need for contrast dye during the implantation of CIEDs. Based on the visualization of the pacing lead tip and accurate anatomic reconstruction of the chamber of interest and a specialized mapping technique, 3D mapping technology dramatically improves the efficacy and success of the advanced cardiac implantable devices' placement. Additionally, it provides a superior option for those with complex medical conditions. CONCLUSION: The use of 3D mapping technology in CIEDs has been proven feasible and effective by accumulating evidence. It is fair to anticipate that it will be widely used in CIED implantation in the future.

Thiosulfate driving bio-reduction mechanisms of scorodite in groundwater environment.

Reductive dissolution of scorodite results in the release and migration of arsenic (As) in groundwater. The purpose of this study was to explore the possible abiotic and biotic reduction of scorodite in groundwater environment and the effect of microbial-mediated sulfur cycling on the bio-reduction of scorodite. Microcosm experiments consisting of scorodite with bacterium Citrobacter sp. JH012-1 or free sulfide were carried out to determine the effects of thiosulfate on the mobilization of As/Fe. The results show arsenic release is positively correlated with iron reduction. The arsenate [As(V)] released can agglomerate with Fe(II) on the surface of scorodite to form crystalline parasymplesite, while no parasymplesite was detected in the abiotic reduction of scorodite by sulfide. The reduction of scorodite and As(V) was affected by thiosulfate. When 0.5 mM thiosulfate was added, the Fe(III) reduction rate increased from 32% to 82%, and the As(V) reduction rate rose from 54% to 64%. When the addition of thiosulfate was increased from 0.5 mM to 2 mM and 5 mM, Fe(III) reduction rate added 4% and 8%, and As(V) reduction rate increased 11% and 16%, respectively. In addition, the presence of thiosulfate promoted the scorodite almost completely converting to parasymplesite. Therefore, the effect of microbial-mediated sulfur cycling should be considered in arsenic migration and reduction from scorodite.

Role of Al substitution in the reduction of ferrihydrite by Shewanella oneidensis MR-1.

Substitution of aluminum under natural environmental conditions has been proven to inhibit the transformation of weakly crystalline iron (oxyhydr)-oxides towards well crystalline iron oxides, thereby enhancing their long-term stability. However, exploration on the role of aluminum substitution in bacteria-mediated iron oxides transformation is relatively lacking, especially in the anaerobic underground condition where iron (oxyhydr)-oxides are easy to reduced. In this study, we selected four different levels of substitution aluminum prevalent in iron oxides under natural conditions, which are 0 mol%, 10 mol%, 20 mol%, and 30 mol% (mol Al/mol (Al + Fe)) respectively. With the presence of Shewanella oneidensis MR-1, we conducted a 15-day anaerobic microcosm experiment in simulated groundwater conditions. The experiment data suggested that aluminum substitution result in a decrease in bio-reduction rate constants of ferrihydrite from 0.24 in 0 mol% Al to 0.17 in 30 mol% Al. Besides, when containing substituted aluminum, secondary minerals produced by biological reduction of ferrihydrite changed from magnetite to akaganeite. These results were attributed to the surface coverage of Al during the reduction process, which affects the contact between S. oneidensis MR-1 and the unexposed Fe(III), thus inhibiting the further reduction of ferrihydrite. Since iron (oxyhydr)-oxides exhibit a strong affinity on multiple kinds of pollutants, results in this study may contribute to predicting the migration and preservation of contaminants in groundwater systems.

Radical adducts formation mechanism of CH3CO2∙ and CH3CO3∙ realized decomposition of chitosan by plasma catalyzed peracetic acid.

High-molecular-weight chitosan has limited applications due to unsatisfactory solubility and hydrophilicity. Discharge plasma coupled with peracetic acid (PAA) oxidation ("plasma+PAA") realized fast depolymerization of high-molecular-weight chitosan in this study. The molecular weight of chitosan rapidly declined to 81.1 kDa from initial 682.5 kDa within 60 s of "plasma+PAA" treatment, and its reaction rate constant was 12-fold higher than single plasma oxidation. Compared with 1O2, ∙CH3, CH3O2·, and O2∙-, CH3CO2∙ and CH3CO3∙ played decisive roles in the chitosan depolymerization in the plasma+PAA system through mechanisms of radical adduct formation. The attacks of CH3CO2∙ and CH3CO3∙ destroyed the ß-(1,4) glycosidic bonds and hydrogen bonds of chitosan, leading to generation of low-molecular-weight chitosan; the main chain structure of chitosan was not changed during the depolymerization process. Furthermore, the generated low-molecular-weight chitosan exhibited greater antioxidant activities than original chitosan. Overall, this study revealed the radical adduct formation mechanisms of CH3CO2∙ and CH3CO3∙ for chitosan decomposition, providing an alternative for fast depolymerization of high-molecular-weight chitosan.

Comparative cost analysis of implanting devices in different cardiac resynchronization therapeutic strategies.

BACKGROUND: Cardiac resynchronization therapy (CRT) is an established treatment option for heart failure patients. However, the implementation of triple-chamber pacemakers can be cost-prohibitive. His-Purkinje system pacing (HPSP) can also enable cardiac resynchronization, and it can be achieved with relatively inexpensive conventional pacemakers. HYPOTHESIS: This article aims to comparatively evaluate the cost of implanting devices in different CRT strategies to provide meaningful guidance for clinical decision-making by electrophysiologists. METHODS: Data was collected on the prices, designed life, and price/designed life of multiple mainstream models of CRT-P, CRT-D, dual-chamber pacemakers, and single-chamber pacemakers that were sold in the Chinese market in 2022. The prices, designed lives, and price/designed life of different pacemaker models were then compared. RESULTS: The costs of CRT-P and CRT-D (13008.44 ± 2752.30 USD and 22043.36 ± 3676.25 USD) were significantly higher than those of conventional pacemakers (dual-chamber: 11142.39 ± 4273.85 USD and single-chamber: 5634.28 ± 2032.80 USD) (p < .05). Additionally, the price/designed life of conventional pacemakers (dual-chamber: 839.63 ± 258.62 US dollar/year and single-chamber: 435.86 ± 125.44 US dollar/year) was significantly better than that of CRT-P and CRT-D (1386.91 ± 266.73 and 2585.53 ± 520.27 US dollar/year, respectively) (p < .05). CONCLUSION: Conduction system pacing (CSP)-based CRT is more cost-effective than BVP-based CRT. Furthermore, CSP-based CRT can achieve cardiac resynchronization with conventional pacemakers and may be a good option for HF patients who do not need defibrillation.

RNAi-Based Antiviral Innate Immunity in Plants.

Multiple antiviral immunities were developed to defend against viral infection in hosts. RNA interference (RNAi)-based antiviral innate immunity is evolutionarily conserved in eukaryotes and plays a vital role against all types of viruses. During the arms race between the host and virus, many viruses evolve viral suppressors of RNA silencing (VSRs) to inhibit antiviral innate immunity. Here, we reviewed the mechanism at different stages in RNAi-based antiviral innate immunity in plants and the counteractions of various VSRs, mainly upon infection of RNA viruses in model plant Arabidopsis. Some critical challenges in the field were also proposed, and we think that further elucidating conserved antiviral innate immunity may convey a broad spectrum of antiviral strategies to prevent viral diseases in the future.

Effects of Sulfide Input on Arsenate Bioreduction and Its Reduction Product Formation in Sulfidic Groundwater.

Microbes have important impacts on the mobilization of arsenic in groundwater. To study the effects of sulfide on As(V) bioreduction in sulfidic groundwater, Citrobacter sp. JH012-1 isolated from sediments in the Jianghan Plain was used in a microcosm experiment. The results showed that sulfide significantly enhanced As(V) bioreduction as an additional electron donor. The reduction rates of As(V) were 21.8%, 34.5%, 73.6% and 85.9% under 0, 15, 75 and 150 µM sulfide inputting, respectively. The main products of As(V) bioreduction were thioarsenite and orpiment and the concentration of thioarsenite reached to 5.5 and 7.1 µM in the solution with the initial 75 and 150 µM sulfide, respectively. However, under 0 and 15 µM sulfide inputting, the dominant product was arsenite with no thioarsenite accumulation. The decrease in pH enhanced the bioreduction of As(V) and promoted the formation of thioarsenite and orpiment. In addition, the percentage of thioarsenite in total arsenic decreased with the decrease in the ratio of sulfur to arsenic, indicating that the formation of thioarsenite was limited by the concentration of initial sulfide. Therefore, the presence of sulfide had a significant effect on the transformation of arsenic in groundwater. This study provides new insights into the bioreduction of As(V) and the formation of thioarsenite in sulfidic groundwater.

Effects of Calcium on Arsenate Adsorption and Arsenate/Iron Bioreduction of Ferrihydrite in Stimulated Groundwater.

The reduction and transformation of arsenic-bearing ferrihydrite by arsenate-iron reducing bacteria is one of the main sources of arsenic enrichment in groundwater. During this process the coexistence cations may have a considerable effect. However, the ionic radius of calcium is larger than that of iron and shows a low affinity for ferrihydrite, and the effect of coexisting calcium on the migration and release of arsenic in arsenic-bearing ferrihydrite remains unclear. This study mainly explored the influence of adsorbed Ca2+ on strain JH012-1-mediated migration and release of arsenate in a simulated groundwater environment, in which 3 mM ferrihydrite and pH 7.5. Ca2+ were pre-absorbed on As(V)-containing ferrihydrite with a As:Fe ratio of 0.2. Solid samples were analyzed by X-ray diffraction (XRD), scanning electron microscopic (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The results show that calcium and arsenate can synergistically adsorb on ferrihydrite due to the electrostatic interactions, and the adsorbed Ca2+ mainly exists on the surface through the outer-sphere complex. Adsorbed Ca2+ entering the stimulated groundwater was easily disturbed and led to an extra release of 3.5 mg/L arsenic in the early stage. Moreover, adsorbed Ca2+ inhibited biogenic ferrous ions from accumulating on ferrihydrite. As a result, only 12.30% Fe(II) existed in the solid phase, whereas 29.35% existed without Ca2+ adsorption. Thus, the generation of parasymplesite was inhibited, which is not conducive to the immobilization of arsenic in groundwater.

Success rates, challenges and troubleshooting of left bundle branch area pacing as a cardiac resynchronization therapy for treating patients with heart failure.

Cardiac resynchronization therapy (CRT) is an important treatment of heart failure patients with reduced left ventricular ejection fraction (LVEF) and asynchrony of cardiac electromechanical activity. Left bundle branch area pacing (LBBaP) is a novel physiological pacing modality that appears to be an effective method for CRT. LBBaP has several advantages over the traditional biventricular-CRT (BiV-CRT), including a low and stable pacing capture threshold, a high success rate of implantation, a short learning curve, and high economic feasibility. However, LBBaP is not suitable for all heart failure patients needing a CRT and the success rates of LBBaP in heart failure patients is lower because of myocardial fibrosis, non-specific intraventricular conduction disturbance (IVCD), enlargement of the right atrium or right ventricle, etc. In this literature review, we summarize the success rates, challenges, and troubleshooting of LBBaP in heart failure patients needing a CRT.

Synergy between indigenous bacteria and extracellular electron shuttles enhances transformation and mobilization of Fe(III)/As(V).

The reduction of Fe(III) by metal-reducing bacteria through extracellular electron transfer (EET) is a critical link in the biogeochemical cycle of As/Fe, and humic substances are believed to play a role in this process. In this study, the indigenous As-resistant bacterium Bacillus D2201 isolated from the Datong Basin was responsible for the valence transition of Fe and As in the groundwater environment. The bacterium has both the arsC gene for intracellular arsenate reduction and an EET pathway for transferring electrons to an electrode or Fe(III). Chronoamperometry showed that 3.0- and 10.2-fold increases in the output current density were achieved by injecting 0.05 and 0.5 mM AQDS with an inoculation of Bacillus D2201. Interestingly, Fe(III) bio-reduction is not only regulated by AQDS, but also by As(V) stimulation. The increase in pyruvate consumption and levels of intracellular glutathione (GSH) suggest that As pressure promotes cell metabolism and the consumption of electron donors for Fe(III) reduction with strain D2201. The reduction and dissolution of Fe(III) mineral regulated by AQDS dominated the release and mobilization of As. Compared with the AQDS-free treatment, 5.5-, 6.6-, and 7.2-fold increases in the amounts of Fe(II) were released with the addition of 0.1, 0.5, and 1 mM AQDS, respectively, and approximately 2.6-, 2.8-, and 3.2-fold increases in the As(V) levels were observed under the same conditions. These insights have profound environmental implications with respect to the effect of AQDS and As stress on EET and Fe(III) reduction in arsenic-resistant bacteria.

Kaolin-Enhanced Superabsorbent Composites: Synthesis, Characterization and Swelling Behaviors.

One type of low-cost and eco-friendly organic‒inorganic superabsorbent composite (SAPC) was synthesized by free radical polymerization of acrylic acid (AA), starch (ST), sodium alginate (SA) and kaolin (KL) in aqueous solution. The structure and morphology of the SAPC were characterized by Fourier transform infrared spectrometer (FT-IR), scanning electron microscope (SEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The influence of different reaction conditions on water absorption of SAPC, i.e., SA and KL contents, AA neutralization degree (ND), potassium persulfate (KPS) and N, N'-methylenebisacrylamide (MBA) loading were systematically studied. Under the optimal synthesis conditions, very high water absorption of 1200 g/g was achieved. The swelling kinetic mechanism of SAPC was studied by pseudo-second order swelling kinetics model and Ritger‒Peppas model. The performances of SAPC under different environments were tested and results revealed that this new SAPC had excellent swelling capacity, high water retention, good salt tolerance in monovalent salt solution (NaCl solution) and good pH tolerance between 4 and 10.

An indigenous bacterium Bacillus XZM for phosphate enhanced transformation and migration of arsenate.

A number of arsenate-reducing bacteria respire adsorbed As(V), producing As(III) and thus contributing to arsenic mobilization from the solid phase to the aqueous phase. Two arsenate reducing genes, arsC and arrA, were both amplified in an indigenous bacterium Bacillus XZM isolated from high arsenic aquifer sediments. The effect of phosphate input on this novel bacterium in terms of mediating the biogeochemical behavior of arsenic was investigated for the first time. The results show bacterial growth and arsenate reduction appear to increase with the addition of phosphate. Input of 1 mM phosphate reduced the negative effects of As(V) on bacterial growth, resulting in 55-60% greater biomass production compared to lower phosphate inputs (0.01 and 0.1 mM). The data of real-time quantitative PCR (qPCR) indicated arsenate was involved in the expressions of two arsenate reductase genes (arsC and arrA genes) in indigenous bacterium Bacillus XZM. Overall, the addition of phosphate (from 0.1 to 1 mM) resulted in a doubling of arsenate bio-desorption from the sediment into the aqueous medium. Oxidation-reduction potential, as an environmental indicator of the bacterial reduction of metals, declined to -200 mV in the presence of strain XZM and 1 mM phosphate in the microcosm. Phosphate input enhanced arsenic biomigration, indicating the effect of phosphate concentration should be considered when studying the biogeochemical behavior of arsenic.

Property improvement of multi-walled carbon nanotubes/polypropylene composites with high filler loading via interfacial modification.

Although carbon nanotubes (CNTs) exhibit excellent performance, they are prone to agglomeration because of their high surface energy and large specific surface area. Moreover, CNTs are hardly compatible with polymers due to their nonpolar properties, as manifested by the less stable interface between these two components. This study was aimed at improving the compatibility between multi-walled carbon nanotubes (MWNTs) and polypropylene (PP). Herein, a practical strategy for the modification of MWNTs and the subsequent fabrication of polypropylene-grafted multi-walled carbon nanotubes (PP-g-MWNTs) are reported. The morphology of the as-obtained PP-g-MWNTs was observed using a scanning electron microscope (SEM), a transmission electron microscope (TEM) and a polarizing microscope, whereas their elemental composition and bond structures were characterized by Fourier transform infrared (FT-IR) spectroscopy, energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). X-ray diffraction (XRD) was used for crystallographic analyses. A performance comparison between the PP-g-MWNT samples and the undecorated samples was conducted based on the results obtained via dynamic mechanical analysis (DMA), tensile testing, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Serial characterizations proved the successful grafting of PP molecular chains onto the MWNT surfaces. Thus, the MWNTs, the filler phase, could be included into the PP matrix covalently and thus existed as an integrated component of the composite system. As a consequence, the specific design of PP-g-MWNTs remarkably improved both thermal and mechanical properties of the PP composites.

Interactions between arsenic adsorption/desorption and indigenous bacterial activity in shallow high arsenic aquifer sediments from the Jianghan Plain, Central China.

Exposure to arsenic in the environment is hazardous to biota. Three types of sediments from a shallow, high arsenic aquifer were collected from Jianghan Plain, Central China to investigate interactions between indigenous bacterial activity and arsenic adsorption/desorption. For the same level of bacterial activity, the As(III) or As(V) adsorption rate in sediments decreased from clay loam to loamy sand to silty sand. However, the arsenic desorption rate from these sediments followed the reverse sequence. For the same arsenic speciation and content, bacterial activity decreased from clay loam to loamy sand to silty sand. Overall, arsenic adsorption/desorption rates were related to both bacterial activity and sediment texture. The bacteria present could reduce As(V) to As(III), thereby favoring its release from sediment into solution and increasing the ratio of As(III) to total arsenic. These results indicate indigenous bacteria strongly affect the adsorption/desorption and oxidation-reduction of arsenic, and are actively involved in the dynamic equilibrium of arsenic between sediment and groundwater in this shallow aquifer.