Nuclear alpha-synuclein accelerates cell senescence and neurodegeneration.

BACKGROUND: The progression of Parkinson's disease (PD) is related to ageing. The accumulation of nuclear alpha-synuclein (α-syn) may accelerate the occurrence of neurodegenerative diseases, but its role in PD remains poorly understood. METHODS: In the present study, α-syn expression was specifically targeted to the nucleus by constructing an adeno-associated virus (AAV) vector in which a nuclear localization sequence (NLS) was added to the α-syn coding sequence. Virus-mediated gene transfer, behavioural tests, RNA-Seq, immunohistochemistry, western blotting, and quantitative real-time PCR were then performed. RESULTS: In vivo experiments using a mouse model showed that nuclear α-syn increased the severity of the PD-like phenotype, including the loss of dopaminergic neurons concomitant with motor impairment and the formation of α-syn inclusions. These nuclear inclusions contained α-syn species of high molecular weights and induced strong transcriptional dysregulation, especially induced high expression of p21 and senescence-associated secretory phenotype (SASP)-related genes. In addition, the transcriptional alterations induced by nuclear α-syn were associated with gliosis, inflammation, oxidative and DNA damage, and lysosomal dysfunction, and they eventually accelerated neuronal loss and neurodegeneration. CONCLUSIONS: Our results suggest that nuclear α-syn plays a crucial role in PD pathogenesis.

Pan-cancer analysis and experimental validation revealed the m6A methyltransferase KIAA1429 as a potential biomarker for diagnosis, prognosis, and immunotherapy.

BACKGROUND: KIAA1429, also known as VIRMA (vir-like m6A methyltransferase associated), plays a crucial role in tumorigenesis by modulating the level of m6A methylation. Previous studies have reported the prevalent overexpression of KIAA1429 in multiple cancers, related to a poor prognosis. Nevertheless, the precise role of KIAA1429 in tumor progression and its impact on the immune response remains unclear. METHODS: A differential analysis of KIAA1429 expression was performed across cancers using data from the Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) databases. We evaluated the role of KIAA1429 in the diagnosis, prognosis, and immunotherapy of tumor patients using bioinformatics methods. In addition, we also analyzed the associations between KIAA1429 and DNA methylation, immunotherapy. RT-qPCR was used to study the expression levels of KIAA1429 mRNA in 11 cell lines. RESULTS: KIAA1429 is found to be overexpressed in 28 cancer types, but its expression is relatively low in patients with acute myeloid leukemia (LAML) and ovarian serous cystadenocarcinoma (OV). Moreover, KIAA1429 demonstrates a positive correlation with advanced stages of multiple cancers. Kaplan-Meier (KM) analysis suggested that patients with elevated KIAA1429 expression had shorter survival. Furthermore, KIAA1429 shows strong associations with DNA methylation, tumor-infiltrating immune cells (TIICs), and the tumor microenvironment (TME). RT-qPCR results indicated significantly higher expression of KIAA1429 in tumor cells compared to matched-normal cells. CONCLUSIONS: In summary, our work illustrates that KIAA1429 expression is positively connected with poor prognosis in multiple cancers. Moreover, KIAA1429 could serve as a diagnostic factor and a predictor of immune response for specific tumor types.

The effectiveness of problem-based learning compared with lecture-based learning in surgical education: a systematic review and meta-analysis.

BACKGROUND: This meta-analysis was conducted to systematically evaluate the impact of problem-based learning (PBL) and lecture-based learning (LBL) teaching models on students' learning in surgical education. METHODS: We systematically searched the publications related to the application of PBL and LBL in surgical courses in PubMed, Embase, Web of Science and Cochrane Library databases, the last retrieval time is September 20, 2022. After screening the literature according to the inclusion and exclusion criteria, extracting data and evaluating the methodological treatment of the included studies, Stata 17.0 software was used to perform meta-analysis. RESULTS: Nine studies were included totally. The results showed that compared with LBL, PBL was superior in clinical competence (SMD = 0.81, 95% CI: 0.12 ~ 1.49, P = 0.020) and student satisfaction (SMD = 2.13, 95% CI: 1.11 ~ 3.15, P < 0.0001) with significant differences. But the comprehensive scores (SMD = 0.26, 95% CI: -0.37 ~ 0.89, P = 0.421) and theoretical knowledge (SMD=-0.19, 95% CI: -0.71 ~ 0.33, P = 0.482) to PBL and LBL had no significant difference. CONCLUSION: This study showed that the PBL teaching model is more effective than the LBL teaching model in surgical education on the aspects of enhancing clinical competence and student satisfaction. However, further well-designed studies are needed to confirm our findings.

Association between CD8+ tumor-infiltrating lymphocytes and prognosis of non-small cell lung cancer patients treated with PD-1/PD-L1 inhibitors: a systematic review and meta-analysis.

BACKGROUND: A meta-analysis method was used to investigate the prognostic value of CD8+ tumor-infiltrating lymphocytes (TILs) in non-small cell lung cancer (NSCLC) patients treated with PD-1/PD-L1 inhibitors. METHODS: A database search of PubMed, Embase, Web of Science and Cochrane Library up until 7 February, 2023. A clinical study on the relationship between CD8+ TILs and PD-1/PD-L1 inhibitors in the therapeutics of NSCLC. RevMan 5.3 and StataMP 17.0 software were used for meta-analysis. The outcome indicators incorporated overall survival (OS), progression-free survival (PFS) and objective response rate (ORR). RESULTS: Nineteen articles with 1488 patients were included. The analysis results showed that high CD8+ TILs were associated with better OS (HR = 0.60, 95% CI: 0.46-0.77; P < 0.0001), PFS (HR = 0.68, 95% CI: 0.53-0.88; P = 0.003) and ORR (OR = 2.26, 95% CI: 1.52-3.36; P < 0.0001) in NSCLC patients treated with PD-1/PD-L1 inhibitors. Subgroup analysis indicated that patients with high CD8+ TILs had good clinical prognostic benefits whether the location of CD8+ TILs was intratumoral or stromal, and compared with East Asian, high CD8+ TILs in Caucasians showed a better prognosis. High CD8+ TILs in peripheral blood did not improve OS (HR = 0.83, 95% CI: 0.69-1.01; P = 0.06) and PFS (HR = 0.93, 95% CI: 0.61-1.14; P = 0.76) in NSCLC patients receiving PD-1/PD-L1 inhibitors. CONCLUSION: In spite of the location of CD8+ TILs, high densities of CD8+ TILs were predictive of treatment outcomes in NSCLC patients treated with PD-1/PD-L1 inhibitors. However, high CD8+ TILs in peripheral blood had no predictive effect.

NEAT1 Regulates Calcium Oxalate Crystal-Induced Renal Tubular Oxidative Injury via miR-130/IRF1.

Aims: Calcium oxalate (CaOx) crystal deposition induces damage to the renal tubular epithelium, increases epithelial adhesion, and contributes to CaOx nephrocalcinosis. The long noncoding RNA (lncRNA) nuclear paraspeckle assembly transcript 1 (NEAT1) is thought to be involved in this process. In this study, we aimed to investigate the mechanism by which NEAT1 regulates renal tubular epithelium in response to inflammatory and oxidative injury triggered by CaOx crystals. Results: As CaOx crystals were deposited in mouse kidney tissue, the expression of NEAT1 was significantly elevated and positively correlated with interferon regulatory factor 1 (IRF1), Toll-like receptor 4 (TLR4), and NF-κB. NEAT1 targets and inhibits miR-130a-3p as a competitor to endogenous RNA. miR-130 binds to and exerts inhibitory effects on the 3'-untranslated region of IRF1. After transfected with silence-NEAT1, IRF1, TLR4, and NF-κB were also variously inhibited, and oxidative damage in renal calcinosis was subsequently attenuated. When we simultaneously inhibited NEAT1 and miR-130, renal tubular injury was exacerbated. Innovation and Conclusion: We found that the lncRNA NEAT1 can enhance IRF1 signaling through targeted repression of miR-130a-3p and activate TLR4/NF-κB pathways to promote oxidative damage during CaOx crystal deposition. This provides an explanation for the tubular epithelial damage caused by CaOx crystals and offers new ideas and drug targets for the prevention and treatment of CaOx nephrocalcinosis. Antioxid. Redox Signal. 38, 731-746.

Ocruranus-Eohalobia Sclerites from the Cambrian Stage 2 Yanjiahe Formation in South China: Scleritome Reconstruction and Zoological Affinity.

The isolated sclerites of the Ocruranus and Eohalobia group are abundant among the early Cambrian small shelly fossil assemblages, which were recently assigned to the same scleritome as an early member of the polyplacophoran (chiton) stem lineage. However, the scleritome reconstruction and zoological affinities of these sclerites are still controversial due to the lack of exceptionally preserved articulated specimens with in-situ sclerites. Herein, we report new specimens of Ocruranus and Eohalobia sclerites from Member 5 of the Yanjiahe Formation, which provide new insights into the reconstruction of the original scleritome. The Eohalobia sclerites from the Yanjiahe Formation have an extended and upfolded proximal field with dense wrinkles, which seems to be a weakly mineralized structure and acted as a joint with another sclerite, Ocruranus. Comparing the butterfly-shaped proximal field on a unique sclerite of Eohalobia with the sub-apical field on Ocruranus sclerites suggests that the original scleritome of this group may consist of only two types of sclerites: the Ocruranus-type and the Eohalobia-type. The polygonal structure on the internal mold of Eohalobia sclerites is interpreted herein as the muscle attachment zone; their distribution corresponds well with that of the modern chitons, which provides strong evidence to support the close relationship between the Ocruranus-Eohalobia group and the Polyplacophora.

miR-378 associated with proliferation, migration and apoptosis properties in A549 cells and targeted NPNT in COPD.

Background: microRNAs contribute to the development and progression of chronic obstructive pulmonary disease (COPD). However, the underlying molecular mechanisms are largely unclear. The goal of this study was to investigate the roles of miR-378 in alveolar epithelial type II cells and identify molecular mechanisms which contribute to the pathogenesis of COPD. Materials and methods: Human alveolar epithelial (A549) cells were cultured in Dulbecco's Modified Eagle Medium. Cell proliferation was studied by using a cell counting kit-8 (CCK-8) and colony formation assays. Cell apoptosis and cell cycle were analyzed by flow cytometry and wound healing and Transwell were used to analyze the cell migration and. We performed bioinformatics analysis including target gene prediction, gene ontology (GO), Kyoto Encyclopedia of Genes and Genome (KEGG) pathway enrichment and construction of protein-protein interaction (PPI) network. The expression of miR-378 and NPNT from publically available expression microarray of COPD lung tissues was analyzed. Results: Overexpression of miR-378 significantly increases cell proliferation, migration, and suppress apoptosis. GO analysis demonstrated that the miR-378 involved in transcription, vascular endothelial growth factor receptor signaling pathway, phosphatidylinositol 3-kinase signaling, cell migration, blood coagulation, cell shape, protein stabilization and phosphorylation. Pathway enrichment showed that the 1,629 target genes of miR-378 were associated with mTOR, ErbB, TGF-ß, MAPK, and FoxO signaling pathways. Notably, miR-378 directly targets Nephronectin in A549 cells, and miR-378 was upregulated while NPNT was downregulated in COPD lung tissue samples. Conclusions: These findings suggest that miR-378 can regulate the proliferation, migration, and apoptosis of A549 cells and target NPNT. miR-378 increased in COPD lung tissues while NPNT decreased, and might prove a potential target for novel drug therapy.

Efficient reclamation phosphate by alginate-g-BMOF using poly(N-isopropyl acrylamide-co-acrylamide) as coating for temperature-responsive slow-release P-fertilizer.

Poly(N-isopropyl acrylamide) and its derived copolymer, as a temperature-responsive material, are widely used in the field of anticancer drug carrier. And it also plays an important role as carrier in slow-release fertilizer in recent years. In this paper, a smart poly(N-isopropyl acrylamide-co-acrylamide)-coated Alg-BMOF (PABMOF) was fabricated in ionic liquids microemulsion ([Bmim]PF6/TX-100/water) as nano-reactor. The structure and morphology of PABMOF were characterized by FT-IR, XRD, XPS, SEM, TG and BET. The resultant PABMOF was used as a adsorbent for H2PO4- adsorption. The adsorption kinetics, isotherms and mechanism of H2PO4- onto the resultant PABMOF were studied. The adsorption kinetic data was well suitable for pseudo-second-order kinetic model, and adsorption isotherm results demonstrated that the equilibrium data was fitted for Freundlich model. The water-holding and water-retention capacity of soil with TRSRFs addition of 2 wt% were74.3% and 52.13% at 30th day, respectively. Moreover, the release behavior of TRSRFs in water show that the cumulative release rate (Cr%) were 81.4% at 45 °C and 97.6% at 25 °C within 172 h, which displayed the excellent temperature-responsive property. The effect of TRSRFs on the growth of Chinese cabbage was investigated, which was indexed with the germination rate, plant height and root length of the crop.

Effects of alternative splicing events and transcriptome changes on kidney stone formation.

During the development of urinary stone disease, the formation of tiny crystals that adhere to the renal tubular epithelium induces epithelial cell damage. This damage and repair of the epithelium is associated with the establishment of more crystal adhesion sites, which in turn stimulates further crystal adhesion and, eventually, stone formation. Deposited crystals typically cause changes in epithelial cell gene expression, such as transcriptome changes and alternative splicing events. Although considered important for regulating gene expression, alternative splicing has not been reported in studies related to kidney stones. To date, whether alternative splicing events are involved in the regulation of stone formation and whether crystallographic cell interactions are regulated by alternative splicing at the transcriptional level have remained unknown. Therefore, we conducted RNA sequencing and alternative splicing-related bioassays by modeling the in vitro stone environment. Many alternative splicing events were associated with crystallographic cell interactions. Moreover, these events regulated transcription and significantly affected the capacity of crystals to adhere to renal tubular epithelial cells and regulate apoptosis.

A Comparative Study of Different Stem Cell Transplantation for Spinal Cord Injury: A Systematic Review and Network Meta-Analysis.

OBJECTIVE: In the present study, we evaluated the efficacy and safety of different stem cell types for spinal cord injury (SCI) therapy to determine the superior treatment of SCI. METHODS: A systematic literature search was performed using PubMed, Embase, the Cochrane Library, Web of Science, VIP, Chinese National Knowledge Infrastructure, and Wan Fang databases from initiation to January 30, 2021. A Bayesian network meta-analysis was performed using ADDIS (Aggregate Data Drug Information System) software. The PROSPERO registration number was CRD42020129635. RESULTS: We included 12 studies with 642 patients in the present study. A network meta-analysis revealed that bone mesenchymal stem cells (BMSCs) combined with rehabilitation training were significantly more effective than rehabilitation training alone in improving the American Spinal Injury Association (ASIA) impairment scale grade (odds ratio, 94.25; 95% confidence interval [CI], 6.71-9321.95), ASIA motor score (weighted mean difference [WMD], 6.67; 95% CI, 0.83-12.73), ASIA sensory functional score (WMD, 12.41; 95% CI, 3.42-21.72), and Barthel index (WMD, 7.24; 95% CI, 0.21-14.30). However, no statistically significant differences were observed between bone marrow mononuclear cells (MNCs) combined with rehabilitation training, umbilical cord-derived mesenchymal stem cells (UCMSCs) combined with rehabilitation training, or UCMSCs alone and rehabilitation alone for all indicators. In terms of safety, there were no serious and permanent adverse effects after transplantation of BMSCs, MNCs, or UCMSCs. CONCLUSIONS: BMSCs plus rehabilitation might be superior to other stem cell treatments of SCI in improving the ASIA impairment scale grade, ASIA motor score, ASIA sensory functional score, and Barthel index. The therapeutic effects of UCMSCs and MNCs remain to be confirmed.

Neuritin promotes angiogenesis through inhibition of DLL4/Notch signaling pathway.

Neuritin is a member of the neurotrophic factor family, which plays an important role in the promotion and development of the nervous system. Neuritin is also involved in angiogenesis. Neuritin was recently found to be a negative regulatory factor of the Notch 1 signaling pathway. Notch signaling pathway is known as a regulatory pathway of angiogenesis. Thus, neuritin may play a role in angiogenesis through the Notch signaling pathway. In the present study, we investigated the expressions of neuritin and Notch signaling pathway factors in the pulmonary vascular tissue. The results showed that neuritin expression was increased in the paraneoplastic vascular tissue and decreased in the lung cancer vascular tissue. The neuritin expression was increased with the increase of vascular tissue density, and a negative correlation between neuritin expression and delta-like ligand 4 (DLL4) was identified in vascular tissues of lung cancer. Overexpression of neuritin in human umbilical vein endothelial cells (HUVECs) inhibited the expressions of Notch signaling pathway-associated factors, including DLL4, NICD, and Hes-1, and promoted the migration and tubular formation of HUVECs. In conclusion, our results indicated that neuritin is involved in angiogenesis and may play a role in angiogenesis through the Notch signaling pathway. This study provides a theoretical basis for clinical anti-angiogenesis therapy.

Transcriptomics analysis of the metabolic mechanisms of iron reduction induced by sulfate reduction mediated by sulfate-reducing bacteria.

Sulfate-reducing bacteria (SRB) play an important role in sulfur, iron and carbon cycling. The majority of studies have illustrated the role of SRB in biogeochemical cycling in pure cultures. In this study, we established three SRB enrichment cultures (designated HL, NB and WC) from different paddy soils and conducted a transcriptomic analysis of their metabolic characteristics under sulfate and sulfate-free conditions. In the HL cultures, there was no sulfate consumption but ferrihydrite was reduced. This indicated that bacteria in the HL samples can reduce ferrihydrite and preferentially utilize ferrihydrite as the electron acceptor in the absence of both ferrihydrite and sulfate. Sulfate consumption was equal in the NB and the WC cultures, although more ferrihydrite was reduced in the NB cultures. Transcriptomics analysis showed that (i) upregulation of O-acetylserine sulfhydrylase gene expression indicating sulfate assimilation in the WC samples; (ii) the energy conservation trithionate pathway is commonly employed by SRB and (iii) sulfate not only enhanced iron reduction by its conversion to sulfide but also promoted enzymatic electron transfer via c-type cytochromes.

RNA demethylase Alkbh5 is widely expressed in neurons and decreased during brain development.

N6-methyladenosine (m6A) RNA methylation is one of the most abundant internal modifications on mRNAs and highly enriched within the brain. The demethylation of m6A is regulated by demethylases including fat-mass and obesity-associated protein (FTO) and AlkB homolog 5 (Alkbh5). FTO has been shown to play an important role in the brain, but little is known about the expression pattern and role of Alkbh5. Here, we investigated the expression profile of Alkbh5 in the developing mouse brain and its localization in the adult mouse brain. The results showed that Alkbh5 was widely detected throughout the mouse brain, with relatively high levels observed in the cerebellum and olfactory bulb of the adult mouse brain. Furthermore, Alkbh5 is mainly co-localized with neuronal marker NeuN, suggesting that it is primarily expressed in the neurons. Specifically, Alkbh5 could be found primarily in the nucleus of mouse neurons and cell lines. In addition, Alkbh5 protein decreased dramatically during brain development. Our findings detail the expression pattern and subcellular localization of Alkbh5 in the mouse brain. These results provide a neurobiological basis for the participation of Alkbh5 in the regulation of various brain functions, which might shed new light on further functional analysis of Alkbh5 and m6A in the central nervous system (CNS).

Selenium nanovirus and its cytotoxicity in selenite-exposed higher living organisms.

Selenium (Se) is an essential micronutrient in living organisms, having a narrow margin between essential and potentially toxic intake/exposure. Thus, the biochemistry of Se in living organisms must be studied in-depth to determine the underlying mechanism of Se cytotoxicity. In this study, we report the emergence of selenium nanovirus (SeNVs) in selenite-exposed fish (freshwater and saltwater) and plants (dryland) and its toxicity in them. SeNVs were found in both the abdomen and tail of Oryzias melastigma and saltwater Rhodeus ocellatus, which led to their death. The occurrence of the intracellular assembly of SeNVs was observed in the roots and leaves of corn Zea mays, but not in those of Limnobium laevigatum. SeNVs led to the death of Z. mays but caused chronic toxicity in L. laevigatum. SeNVs should be a system or structure that dissipates the intracellular redox gradients of the host cells, with simple information consisting Se-O, Se-N, or Se-S bond, that would ensure elemental Se ligand binding with nearly specific biomolecules in host cells, thereby maintaining their composition and stabilizing their structure. The multiple toxic effects of Se, therefore, could be the consequence of increase of entropy in the host cells caused by the intracellular assembly of SeNVs. This study may provide an insight into the underlying mechanism of Se in environmental toxicology and its applications in human health.

A study on screening and antitumor effect of CD55-specific ligand peptide in cervical cancer cells.

BACKGROUND: To improve the targeting ability of antitumor drugs, we identified the antigens with high expression on the surface of tumor cells associated with tumor escape, such as the complement regulatory protein CD55 molecule, which is also known as the decay accelerating factor. In this study, phage display technology was used to screen and identify CD55-specific ligand peptide (CD55sp) bound to CD55 molecule on the surface of cervical cancer HeLa cells. We then explored the role of this peptide in inhibiting the growth of cervical cancer cells in vitro. Our characterization of CD55sp will provide implication for tumor target therapy. METHODS: The phage bound to the surface of HeLa cells were isolated by phage display technology. Positive phage clones were identified by ELISA. Phage was then amplified and determined by agarose gel electrophoresis after monoclonal DNA extraction. DNA sequencing and bioinformatical analysis were conducted to obtain specific ligand peptides. Flow cytometry and immunofluorescence were used to measure the expression of CD55 molecule on the surface of tumor and normal cells. Subsequently, the effects of CD55sp on the proliferation and apoptosis of HeLa and SiHa cells were determined by Cell Counting Kit-8 (CCK-8), flow cytometry, and TUNEL assay, respectively. The morphology of apoptotic cells was examined by electron microscope. The distribution of Cleaved caspase-3 was detected by immunofluorescence. The expression of bcl-2 and Cleaved caspase-3 were determined by Western blot. RESULTS: The results showed that the peptide (QVNGLGERSQQM) can bind to the CD55 molecule on the surface of cervical cancer HeLa and SiHa cells as a ligand peptide. It can also effectively inhibit the proliferation of cervical cancer cells and induce cell apoptosis. CONCLUSION: This study demonstrates that CD55sp screened by phage display technology plays a strong antitumor role.

Recombinant neuritin affects the senescence, apoptosis, proliferation, and migration of rat bone marrow-derived mesenchymal stem cells.

OBJECTIVE: To study the effects of recombinant neuritin expressed by Pichia pastoris GS115 on the senescence, apoptosis, proliferation, and migration associated with rat bone marrow-derived mesenchymal stem cells (BMSCs). RESULTS: Recombinant neuritin was purified by Ni-affinity chromatography and identified by western blot and MALDI-TOF spectrometry. The effects of recombinant neuritin on senescence, apoptosis, proliferation, and migration of rat BMSCs WERE investigated. ß-Galactosidase staining indicated that recombinant neuritin administration significantly inhibited BMSCs senescence at 1 µg neuritin/ml. Additionally, recombinant neuritin reduced the number of apoptotic cells at the early stage according to Annexin V/propidium iodide staining and inhibited cell proliferation according to MTT assay results. Moreover wound healing assay results showed that recombinant neuritin promoted BMSCs migration in the neuritin-treatment group. CONCLUSION: Recombinant neuritin affects the senescence, apoptosis, proliferation, migration of rat BMSCs. Our findings offer insight into neuritin function outside of the nervous system.

Sulfur-Driven Iron Reduction Coupled to Anaerobic Ammonium Oxidation.

A new biogeochemical pathway has been suggested to be present in terrestrial ecosystems, linking the nitrogen and iron cycles via ferric iron reduction coupled to anaerobic ammonium oxidation. However, the underlying microbiological process has not been demonstrated to date. Here we report a stable consortium, HJ-4, composed of Anaerospora hongkongensis (85%) and facultative anaerobe, Comamonadaceae (15%), which can process ferrihydrite reduction coupled to anaerobic ammonium oxidation driven by sulfur redox cycling. In this process, A. hongkongensis reduces elemental sulfur, sulfite, and polysulfides to sulfide, which fuels ferrihydrite reduction. Sulfide, elemental sulfur, sulfite, and polysulfides serve as electron shuttles, completing the sulfur cycle between A. hongkongensis and ferrihydrite. In addition, Comamonadaceae shows ammonium oxidation potential under aerobic conditions, with nitrite as the main product. We inferred that Comamonadaceae mediates simultaneous nitrification-denitrification coupled to iron redox cycling through nitrate/nitrite-dependent ferrous oxidation under anaerobic conditions. Hence, we discovered a novel pathway for ferric iron reduction coupled to ammonium oxidation, highlighting the key role of electron shuttles and nitrate/nitrite-dependent ferrous oxidation in this process. The biogeochemical cycling of sulfur, iron, and nitrogen could be coupled in aquatic and terrestrial ecosystems.