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The coupling of microbial dissimilatory manganese (Mn) reduction and nitrogen transformation in anaerobic environment affects the fate of many elemental geochemical cycles. A strain of dissimilatory manganese reducing bacteria (DMRB) named Pantoea sp. MFG10 was isolated for simultaneous reduction of Mn(IV) oxides and NO 3 --N to explore the differential reduction mechanism. The post-reaction precipitates were investigated for researching potential persistent products. The strain MFG10 could achieve 99.86% NO 3 --N removal (1.176 mg L−1 h−1) and 20.97 mg L−1 (0.583 mg L−1 h−1) free Mn(II) yield within 12 and 36 h, respectively. The transient intermediate Mn(III) formed after the reduction of strain MFG10 was utilized in the denitrification process. The restricted Mn reduction behavior in the NO 3 --N and manganese oxide co-reduction system led to the formation of large amounts of Mn(III) by single electron transfer of Mn(IV). Mn(III) acts as electron donor and re-oxidized to constitute a dynamic manganese cycle pathway. Thus, the addition of manganese oxide significantly improved the denitrification efficiency and the fast electron flow formed an abundant Mn(III) secondary minerals on the surface of the manganese oxide. This work will help to understand the more subtle environmental and process-based manganese cycle and inspire new strategies to develop efficient manganese recycling processes for groundwater pollution control. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Strain MFG10 exhibits excellent denitrification and manganese reduction abilities. • MnO 2 promoted the metabolism and induced extracellular secretion by MFG10. • SMP composition changed to improve degradability and redox activity. • The EET process was enhanced by the trapping-solubilizing MnO 2 mechanism of EPS. • Tryptophan-like proteins and PS become potential electron donor precursors. In this study, the manganese (Mn) reduction-coupled denitrification strategy of dissimilatory Mn reducing bacteria was insightfully investigated. Different parameters (MnO 2 level, pH, and temperature) were optimized by kinetic fitting to improve denitrification and Mn reduction effects. The 300 mg L−1 MnO 2 addition achieved 98.72% NO 3 –-N removal in 12 h, which was 54.62% higher than blank group without MnO 2. Scale-up studies showed that the metabolic activity of the bacteria was effectively enhanced by the addition of MnO 2. Besides the deepening of humification in the system, tryptophan-like protein and polysaccharide as potential electron donor precursors revealed remarkable contributions to the extracellular secretion-dependent denitrification process of DMRB. The effect of EPS on Mn reduction depends mainly on the capture of MnO 2 by the LB-EPS layer versus its dissolution in the TB-EPS layer. Ultimately, the EPS possess a dual effect of accelerated denitrification and Mn reduction efficiency due to the enhanced EET process. [ABSTRACT FROM AUTHOR]

The co-existence of heavy metals and nitrate (NO 3 −-N) pollutants in wastewater has been a persistent global concern for a long time. A strain LYF26, which can remove NO 3 −-N, calcium (Ca(II)), and cadmium (Cd(II)) simultaneously, was isolated to explore the properties and mechanisms of synergistic contaminants removal. Different conditions (Cd(II) and Ca(II) concentrations and pH) were optimized by Zero -, Half -, and First - order kinetic analyses to explore the environmental parameters for the optimal effect of strain LYF26. Results of the kinetic analyses revealed that the optimal culture conditions for strain LYF26 were pH of 6.5, Cd(II) and Ca(II) concentrations of 3.00 and 180.00 mg L−1, accompanied by Ca(II), Cd(II), and NO 3 −-N efficiencies of 53.10%, 90.03%, and 91.45%, respectively. The removal mechanisms of Cd(II) using strain LYF26 as a nucleation template were identified as biomineralization, lattice substitution, and co-precipitation. The differences and changes of dissolved organic matter during metabolism were analyzed and the results demonstrated that besides the involvement of extracellular polymeric substances in the precipitation of Cd(II) and Ca(II), the high content of humic acid-like species revealed a remarkable contribution to the denitrification process. This study is hopeful to contribute a theory for further developing microbially induced calcium precipitation used to treat complex polluted wastewater. [Display omitted] • A novel strain LYF26 was isolated for efficient removal of NO 3 −-N, Ca(II) and Cd(II). • Growth conditions of strain LYF26 were optimized by Zero -, Half -, and First -models. • Cd(II) in the form of CdCO 3 and Cd 3 (PO 4) 2 was removed via the MICP process. • Valuable application of MICP process in denitrification and heavy metal removal. [ABSTRACT FROM AUTHOR]

Microbially induced calcium precipitation (MICP) driven by denitrification has attracted extensive attention due to its application potential in nitrate removal from calcium-rich groundwater. However, little research has been conducted on this technique at the molecular level. Here, Pseudomonas WZ39 was used to explore the molecular mechanisms of nitrate-dependent MICP and the effects of Ca2+ on bacterial transcriptional regulation and metabolic response. The results exhibited that appropriate Ca2+ concentration (4.5 mM) can promote denitrification and the production of ATP, EPSs, and SMPs. Genome-wide analysis showed that the nitrate-dependent MICP was accomplished through heterotrophic denitrification and CO 2 capture. During this process, EPS biosynthesis and Ca2+ signaling regulation were involved in the nucleation template supply and Ca2+ homeostasis balance. Untargeted transcriptome- and metabolome-association analyses revealed that the addition of Ca2+ triggered the significant up-regulation in several key pathways, such as transmembrane transporter and channel activities, amino acid metabolism, fatty acid biosynthesis, and carbon metabolism, which played a momentous role in the mineral nucleation and energy provision. The detailed information provided novel insights for understanding the active control of bacteria on MICP, and has great significance for deepening the cognition of groundwater remediation using nitrate-dependent MICP technique. [Display omitted] • Nitrate-dependent MICP were first studied from multi-omics perspective. • Appropriate Ca2+ promoted denitrification and production of ATP, EPSs, and SMPs. • Metabolic pathways of strain WZ39 were revealed using genome-wide sequencing. • The up-regulation of EPS and fatty acid synthesis offered more sites for nucleation. • Carbon metabolism, and transport and channel activities played vital roles in MICP. [ABSTRACT FROM AUTHOR]

[Display omitted] • A powerful microbial immobilized biomaterial, PVA/SA@biochar gel beads were prepared. • Immobilized bioreactor removed nitrate, Mn(II), and phenol efficiently. • Manganese oxidation combined with adsorption to remove phenol. • Phenol stress reduced the diversity and abundance of microbial communities. • High-throughput showed that Zoogloea sp. played a vital role in the bioreactor. Water pollutants, such as nitrate, heavy metals, and organics have attracted attention due to their harms to environmental and biological health. A novel polyvinyl alcohol/sodium alginate with biochar (PVA/SA@biochar) gel beads immobilized bioreactor was established to remove nitrate, manganese, and phenol. The optimum conditions for preparing gel beads were studied by response surface methodology (RSM). Notably, the removal efficiencies of nitrate, Mn(II), and phenol were 94.64, 72.74, and 93.97% at C/N of 2.0; the concentrations of Mn(II) and phenol were 20 and 1 mg L−1, respectively. Moreover, addition of different concentrations of phenol significantly affected the components of dissolved organic matter, bacterial activity, and bioreactor performance. The biological manganese oxide (BMO) with three-dimensional petal-type structure produced during Mn(II) oxidation showed excellent adsorption capacity. The removal of phenol relied on a combination of biological action and adsorption processes. High-throughput analysis showed that Zoogloea sp. was the predominant bacterial group. [ABSTRACT FROM AUTHOR]

[Display omitted] • Modified loofah with rough porous structure exhibited great immobilization effect. • Maximum NO 3 –-N, Mn (II) and TC removal efficiency were 91.97, 71.25, and 57.39%. • Adsorption, oxidation and co-metabolism were responsible for TC removal. • Zoogloea sp. was regarded as dominant contributor in the operation of bioreactor. • Metagenome revealed the potential of reactor for NO 3 –-N, Mn(II), and TC removal. The remediation of multiple pollutants in water, for instance, nitrate, heavy metals, and antibiotics is urgent and necessary for the global water resources protection. Herein, a modified loofah bioreactor was designed for simultaneous denitrification, manganese (Mn) oxidation, and tetracycline (TC) removal. The maximum removal efficiencies of NO 3 –-N (91.97%), Mn(II) (71.25%), and TC (57.39%) were achieved at a hydraulic retention time (HRT) of 9 h, Mn(II) concentration of 20 mg L-1, and TC concentration of 1 mg L-1. SEM and XRD were carried out to characterize the bioprecipitation in the operation of bioreactor. TC addition affected the gaseous denitrification products, dissolved organic matter, as well as reduced the OTU in the bioreactor. The Zoogloea were regarded as the dominant species in the microbial community and played an essential role in the operation of bioreactor. Metagenomic analysis proved the great potential for denitrification, manganese oxidation, and antibiotic removal of loofah bioreactor. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new microbial immobilized carrier, PVA/SA@sponge cube was synthesized. • Immobilized bioreactor has the ability to simultaneously remove NO 3 −-N, Mn(II) and TC. • As an electron donor, Mn(II) was transformed into MnO 2 and MnCO 3 by microorganism. • Zoogloea was proved as the dominant contributor in reactor operation. The co-existence of nitrate, manganese (Mn), and antibiotics are of a wide concern. In this study, a denitrifying and manganese-oxidizing Zoogloea Q7 bacterium was immobilized using polyvinyl alcohol/sodium alginate with sponge cube (PVA/SA@sponge cube) in the reactor. The optimal operation parameters of the bioreactor were explored. Maximum nitrate, Mn(II), and tetracycline (TC) removal efficiencies of 93.00, 72.34, and 57.32% were achieved with HRT of 10 h, pH of 6.5, Mn(II) concentration of 20 mg L−1, and TC of 1 mg L−1, respectively. Fluorescence excitation-emission matrix (EEM) proved that the microorganism in the bioreactor was greatly active. Scanning electron microscope (SEM) images demonstrated that Zoogloea Q7 was commendably immobilized on the novel material. X-ray diffraction (XRD) analysis suggested that the bioprecipitate was mainly composed of MnO 2 and MnCO 3. Through high-throughput analysis, Zoogloea sp. Q7 was considered to be the dominant bacteria present in the bioreactor. [ABSTRACT FROM AUTHOR]