APPLIED AND ENVIRONMENTAL MICROBIOLOGY
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2017
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IF 3.807
Wenjun Yu,Rongshui Wang,Haiyan Huang,Huijun Xie,Shuning Wang
Agrobacterium tumefaciens S33 can grow with nicotine as the sole source of carbon, nitrogen, and energy via a novel hybrid of the pyridine pathway and the pyrrolidine pathway. Characterization of the enzymes involved in the hybrid pathway is important for understanding its biochemical mechanism. Here, we report that the molybdenum-containing nicotine dehydrogenase (NdhAB), which catalyzes the initial step of nicotine degradation, is located in the periplasm of strain S33, while the 6-hydroxynicotine oxidase and 6-hydroxypseudooxynicoine oxidase are in the cytoplasm. This is consistent with the fact that NdhA has a Tat signal peptide. Interestingly, an open reading frame (ORF) adjacent to the ndhAB gene was verified to encode a copper-containing electron carrier, pseudoazurin (Paz), which has a signal peptide typical of bacterial Paz proteins. Both were transported into the periplasm after being produced in the cytoplasm. We purified NdhAB from the periplasmic fraction of strain S33 and found that with Paz as the physiological electron acceptor, NdhAB catalyzed the hydroxylation of nicotine at a specific rate of 110.52 ± 8.09 μmol · min−1 · mg of protein−1, where the oxygen atom in the hydroxyl group of the product 6-hydroxynicotine was derived from H2O. The apparent Km values for nicotine and Paz were 1.64 ± 0.07 μM and 3.61 ± 0.23 μM, respectively. NAD(P)+, O2, and ferredoxin could not serve as electron acceptors. Disruption of the paz gene disabled the strain for nicotine degradation, indicating that Paz is required for nicotine catabolism in the strain. These findings help our understanding of electron transfer during nicotine degradation in bacteria.IMPORTANCE Nicotine is a toxic and addictive N-heterocyclic aromatic alkaloid produced in tobacco. Its catabolism in organisms and degradation in tobacco wastes have become major concerns for human health and the environment. Bacteria usually decompose nicotine using the classical strategy of hydroxylating the pyridine ring with the help of activated oxygen by nicotine dehydrogenase, which binds one molybdopterin, two [2Fe2S] clusters, and usually one flavin adenine dinucleotide (FAD) as well. However, the physiological electron acceptor for the reaction is still unknown. In this study, we found that the two-component nicotine dehydrogenase from Agrobacterium tumefaciens S33, naturally lacking an FAD-binding domain, is located in the periplasmic space and uses a copper-containing electron carrier, pseudoazurin, as its physiological electron acceptor. We report here the role of pseudoazurin in a reaction catalyzed by a molybdopterin-containing hydroxylase occurring in the periplasmic space. These results provide new biochemical knowledge on microbial degradation of N-heterocyclic aromatic compounds.
研究领域:
微生物学
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生物化学
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环境科学
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分子生物学
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DOI
PubMed
高影响因子
WATER RESEARCH
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2025
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IF 12.4
Huajing Zhou,Kun Wang,Liang He,Zilian Liu,Dianchao Kong,Qiang Zhang,Song Jin,Ying Han,Qingqing Guan,Guoping Sheng
Groundwater remediation presents significant challenges, while microbial electrocatalytic remediation is promising but suffers from low efficiency due to low periplasmic electron transfer. Unlike traditional methods, which involve directly improving the conditions for electron transfer, herein, we first developed an electron-enhanced proton motive force (PMF) strategy for effective Cr(VI) removal. The proton is used as a new mutagenic source to mutate microorganisms by coupling with a micro-electric field. Interestingly, the dominant bacterial species of Rhizobium can directly capture protons (H + ) and electrons from the cathode as energy sources, resulting in greater than 97% reduction and immobilization of Cr(VI) in groundwater. Since the increase in the proton concentration gradient across the cytoplasmic membrane is due to the free diffusion of protons through new proton transfer channels, the extracellular electron transfer (EET) process is accelerated significantly, and Cr(VI) can also shuttle inside the cell to be reduced. 13 C isotope tracer technology and genetic volcano maps were used to further monitor the active transmembrane ETC transport pathway. The accumulated H + transfers electrons through reduced coenzymes, such as glycoside hydrolases (GH3, GH13-40, and GH5-15) and beta-galactosidase (CBM43), establishing a new transmembrane transfer pathway in the periplasmic space. In addition, unlike conventional bioremediation techniques, the proton gradient intensifies the motive force (PMF-H + ) to accelerate the synthesis of adenosine triphosphate, which provides energy for the bioremediation of Cr(VI), leading to a high bioelectrocatalytic rate. The new PMF-H + strategy successfully restored Cr(VI)-contaminated groundwater in situ to meet the water quality standard, indicating great potential for groundwater remediation.
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DOI
PubMed
高影响因子
mSystems
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2022
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IF 7.324
Zhe Zhao,Ying Xu,Bo Jiang,Qingsheng Qi,Ya-Jie Tang,Mo Xian,Jichao Wang,Guang Zhao
The two-component system CpxRA can sense environmental stresses and regulate transcription of a wide range of genes for the purpose of adaptation. Despite extensive research on this system, the identification of the CpxR regulon is not systematic or comprehensive. Herein, genome-wide screening was performed using a position-specific scoring matrix, resulting in the discovery of more than 10,000 putative CpxR binding sites, which provides an extensive and selective set of targets based on sequence. More than half of the candidate genes ultimately selected (73/97) were experimentally confirmed to be CpxR-regulated genes through experimental analysis. These genes are involved in various physiological functions, indicating that the CpxRA system regulates complex cellular processes. The study also found for the first time that the CpxR-regulated genes ydeE, xylE, alx, and galP contribute to Escherichia coli resistance to acid stress, whereas prlF, alx, casA, yacH, ydeE, sbmA, and ampH contribute to E. coli resistance to cationic antimicrobial peptide stress. Among these CpxR-regulated genes, ydeE and alx responded to both stressors. In a similar way, a cationic antimicrobial peptide is capable of directly activating the periplasmic domain of CpxA kinase in vitro, which is consistent with the CpxA response to acid stress. These results greatly expand our understanding of the CpxRA-dependent stress response network in E. coli.IMPORTANCE CpxRA system is found in many pathogens and plays an essential role in sensing environmental signals and transducing information inside cells for adaptation. It usually regulates expression of specific genes in response to different environmental stresses and is important for bacterial pathogenesis. However, systematically identifying CpxRA-regulated genes and elucidating the regulative role of CpxRA in bacteria responding to environmental stress remains challenging. This study discovered more than 10,000 putative CpxR binding sites based on sequence. This bioinformatics approach, combined with experimental assays, allowed the identification of many previously unknown CpxR-regulated genes. Among the novel 73 CpxRA-regulated genes identified in this study, the role of nine of them in contributing to E. coli resistance to acid or cationic antimicrobial peptide stress was studied. The potential correlation between these two environmental stress responses provides insight into the CpxRA-dependent stress response network. This also improves our understanding of environment-bacterium interaction and Gram-negative pathogenesis.
研究领域:
微生物学
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分子生物学
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细菌致病机制
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基因组学
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生物信息学
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DOI
PubMed
高影响因子
Journal of Environmental Chemical Engineering
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2023
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IF 7.7
Yuan Chen,Yuancai Chen,Yexia Qin
In the present study, we found that nanoparticles (Pd-NPs) were biosynthesized by Bacillus wiedmannii MSM ( B. wiedmannii MSM) with endogenous carbon under O 2 condition, and more favorablity under N 2 purging condition. XRD results indicated that crystal planes of Pd-NPs were attributed to Pd 0 (111), Pd 0 (200), Pd 0 (220), and Pd 0 (311), respectively. TEM and STEM-EDX results showed that the bio-reduction of Pd (II) ( k pd,1 =4.799 min −1 ) occurred predominately in periplasm space. FTIR results showed that the -COOH, -OH, and -NH 2 were the main groups participating in the removal of Pd (II). The aerobic reduction of Pd (II) by B. wiedmannii MSM was proposed, including extracellular superoxide radicals produced by NAD(P)H oxidases , endogenous electron donors, and O 2 -insensitive hydrogenase. These studies provide new methods and insights for reduction of Pd (II).
研究领域:
环境科学
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材料科学
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微生物学
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化学
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产品关联
DOI
高影响因子
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