厌氧氨氧化菌驱动脱氮途径的研究进展

厌氧氨氧化菌(anaerobic ammonia-oxidizing bacteria, AnAOB)的代谢多样性,使得该菌群能够在海洋、湿地和陆地等不同的自然生态系统中广泛分布,甚至在一些极热和极寒环境中也检测到了该菌群的存在。本文回顾并总结了厌氧氨氧化菌在不同生态系统中的发现、分布及脱氮贡献等方面的研究,分析了厌氧氨氧化菌分布的主要环境影响因素。该综述将帮助我们更好地理解全球氮循环中厌氧氨氧化菌的实际角色和功能,并基于厌氧氨氧化(anaerobicammoniaoxidation,anammox)过程,探究能与其进行协作的新型生物脱氮工艺,以期为这些工艺的研发和推广提供生态学基础和新的思考,从而实现脱氮工艺的技术变革。     

细菌Ⅵ型分泌系统效应蛋白的装配及功能的研究进展

蛋白分泌作为细胞之间传递信号的途径之一,在微生物生存竞争中也扮演着重要的角色。革兰氏阴性菌可以通过Ⅵ型分泌系统(type Ⅵ secretion system, T6SS)将效应蛋白传递至胞外或原核和真核微生物中,从而介导微生物间的竞争或宿主-细菌的相互作用,最终建立竞争优势。本文主要总结了T6SS的结构与组成,并重点对效应蛋白的装配以及其与免疫蛋白的作用机制的研究进展进行阐述,为以后靶向T6SS抗菌药物的研制提供新思路。     

Fine-scale mapping of physicochemical and microbial landscapes of the coral skeleton

The coral skeleton harbours a diverse community of bacteria and microeukaryotes exposed to light, O₂ and pH gradients, but how such physicochemical gradients affect the coral skeleton microbiome remains unclear. In this study, we employed chemical imaging of O₂ and pH, hyperspectral reflectance imaging and spatially resolved taxonomic and inferred functional microbiome characterization to explore links between the skeleton microenvironment and microbiome in the reef-building corals Porites lutea and Paragoniastrea benhami. The physicochemical environment was more stable in the deep skeleton, and the diversity and evenness of the bacterial community increased with skeletal depth, suggesting that the microbiome was stratified along the physicochemical gradients. The bulk of the coral skeleton was in a low O₂ habitat, whereas pH varied from pH 6–9 with depth. Physicochemical gradients of O₂ and pH of the coral skeleton explained the β-diversity of the bacterial communities, and skeletal layers that showed O₂ peaks had a higher relative abundance of endolithic algae, reflecting a link between the abiotic environment and the microbiome composition. Our study links the physicochemical, microbial and functional landscapes of the coral skeleton and provides new insights into the involvement of skeletal microbes in the coral holobiont metabolism.     

Epidermal Growth Factor Inhibits Gap Junctional Communication and Stimulates Serine-Phosphorylation of Connexin43 in WB Cells by a Protein Kinase C-Independent Mechanism

Epidermal growth factor (EGF) stimulated the phosphorylation of connexin43 (Cx43) in WB cells as evidenced by the formation of multiple irnmunoreactive Cx43 proteins of higher molecular mass which were abolished by treatment with alkaline phosphatase. Phosphorylation of Cx43 occurred within 10 min of EGF stimulation, was sustained for 1 h, and was associated with almost complete inhibition of gap junctional communication in these cells. EGF-induced phosphorylation and communication inhibition were retained in cells pretreated with phorbol 12-myristate 13-acetate (PMA) to deplete protein kinase C. These results show that the EGF inhibition of communication is tightly linked to protein kinase C-independent phosphorylation of Cx43. Further, Cx43 phosphorylated in the presence of EGF did not react with phosphotyrosine antibodies and in ³²P_i incorporation experiments was shown to contain only phosphoserine indicating that the tyrosine kinase activity of the EGF receptor was not directly involved.     

Crevice-forming mutants in the rigid core of bovine pancreatic trypsin inhibitor: crystal structures of F22A, Y23A, N43G, and F45A.

Crystal structures of four mutants of bovine pancreatic trypsin inhibitor (F22A, Y23A, N43G, and F45A), engineered to alter their stability properties, have been determined. The mutated residues, which are highly conserved among Kunitz-type inhibitors, are located in the rigid core of the molecule. Replacement of the partially buried bulky residues of the wild-type protein with smaller residues resulted in crevices open to the exterior of the molecule. The overall three-dimensional structure of these mutants is very similar to that of the wild-type protein and only small rearrangements are observed among the atoms lining the crevices.     

Intracellular distribution of the hydrophobic triterpene,bryonolic acid,in cultured cells of Luffa cylindrica L.

Summary Intracellular localization of bryonolic acid, an antiallergic pentacyclic triterpene, in cultured cells of Luffa cylindrica was investigated with reference to the sites of its biosynthesis and accumulation. The results of cell fractionation showed that bryonolic acid was mostly located in the cell wall fraction. The addition of FC-43 emulsion to the culture medium was found to cause the release of bryonolic acid from the cell wall into the medium without affecting cell growth and bryonolic acid production. Under this culture condition, ¹⁴C-labeled sodium acetate administered to the cells was rapidly incorporated into bryonolic acid which was then excreted into the medium within 10 min after administration. Electron microscopic observations suggested that spherical vesicles (ca 0.1 m in diameter) derived from the rough endoplasmic reticulum may be associated with the biosynthesis and excretion of this compound into the cell wall. Furthermore, the activity of 2,3-oxidosqualene cyclase, a key enzyme involved in the biosynthesis of bryonolic acid, was detected in the microsomal fraction containing the endoplasmic reticulum.Abbreviations BA bryonolic acid - ER endoplasmic reticulum - LS Linsmaier-Skoog - NAA 1-naphthaleneacetic acid - MES 2-(N-morpholino)ethanesulfonic acid - PVPP polyvinyl polypyrrolidone