趋磁细菌中的磁接收器

趋磁细菌是一种水生的能够运动的微生物,通常存在于含氧—缺氧的具有垂直化学梯度的沉积物和水柱等过渡区域中.在这种分层环境中,地磁场磁力线作为垂直通道,趋磁细菌在通道中沿着磁力线方向排列,上下运动寻找最佳生存位置.这种现象背后的机制则是趋磁细菌体内磁小体磁接收器的存在.趋磁细菌体内具有磁性的链状排列的磁小体,磁小体链与外磁场相互作用,使趋磁细菌可以沿着磁力线游动,具有极性趋磁性,而这种趋磁性与趋磁细菌趋氧性密切相关,帮助它处于最佳氧化还原生存环境中.本文就主要对趋磁细菌体内的磁小体、磁小体链的物理特征以及磁小体磁接收器的工作模型做简要描述,希望能为相关研究提供借鉴.     

‘Phase transitions’ in bacteria – From structural transitions in free living bacteria to phenotypic transitions in bacteria within biofilms

Phase transitions are common in inanimate systems and have been studied extensively in natural sciences. Less explored are the rich transitions that take place at the micro- and nano-scales in biological systems. In conventional phase transitions, large-scale properties of the media change discontinuously in response to continuous changes in external conditions. Such changes play a significant role in the dynamic behaviours of organisms. In this review, we focus on some transitions in both free-living and biofilms of bacteria. Particular attention is paid to the transitions in the flagellar motors and filaments of free-living bacteria, in cellular gene expression during the biofilm growth, in the biofilm morphology transitions during biofilm expansion, and in the cell motion pattern transitions during the biofilm formation. We analyse the dynamic characteristics and biophysical mechanisms of these phase transition phenomena and point out the parallels between these transitions and conventional phase transitions. We also discuss the applications of some theoretical and numerical methods, established for conventional phase transitions in inanimate systems, in bacterial biofilms.     

海洋用钢在含硫酸盐还原菌的海泥中的应变电化学响应

海洋用钢在海底泥土区常承受具大的应力 ,而应力将对海洋用钢的腐蚀破坏行为产生影响 .本文选用一种常用的海洋用钢 ,采集含有硫酸盐还原菌 (SRB)的天然海泥 ,研究试样在海泥中的腐蚀行为 ,以及试样在有裂纹和无裂纹存在时的电流响应特征     

Intestinal Transport and Biotransformation of Resibufogenin and Cinobufagin in Chan Su via HPLC/APCI-MS~n

In vitro models of human colon carcinoma cell line(Caco-2 cell monolayer) and human intestinal bacteria were used to investigate the intestinal transport and biotransformation of resibufogenin and cinobufagin in Chan Su by HPLC/APCI-MSn. The experimental results of Caco-2 cell monolayer demonstrate that the apparent permeability coefficients(Papp) of resibufogenin and cinobufagin are higher than 10-6 cm/s, which indicates that both resibufogenin and cinobufagin have a good absorption in the small intestine....     

手性毛细管气相色谱法测定微生物产生的环氧化物的对映体组成

在选择的修饰β－环糊精中,２,６－Ｏ－二戊基－３－Ｏ－三氟乙酰基－β环糊精（２,６－Ｏ－ＤＰ－３－Ｏ－ＴＦＡ－β－ＣＤ）是毛细管气相色谱法分离１－氯（溴）－２,３－环氧丙烷对映体较好的手性固定相,环氧丙烷对映体即使在室温下也不能拆分。由五株甲烷利用菌和一株乙烯利用菌产生的３－氯（溴）－１,２－环氧丙烷的对映体组成的测定结果表明,甲烷利用菌形成外消旋环氧化物,乙烯利用菌主要形成（Ｓ）－１－氯－２,３－环氧丙烷     

优良发酵果蔬原酱专用乳酸菌的筛选及鉴定

采用目的平板梯度稀释法,从自然发酵果蔬原浆及中外泡菜老液中分离到22株乳酸菌。采用MRS(pH2.0)初筛平板和MRS(30%葡萄糖)复筛平板,筛选出4株耐酸、耐高糖乳杆菌。对其进行了pH值、酸度、活菌数等果蔬酱发酵性能测试研究,其中两株发酵产酸速度快、发酵性能优异、发酵果蔬酱风     

Growth of aerobic bacteria on alkali- solubilized lignite

Applied Biochemistry and Biotechnology -     

Identifying ligand-binding specificity of the oligopeptide receptor OppA from Bifidobacterium longum KACC91563 by structure-based molecular modeling

As a ATP-binding cassette (ABC) transporter the OppA receptor plays key roles in protecting the host organism and transporting nutrients across the intestine by the oligopeptide transporter from symbiotic bacteria and directs maturation of the host immune system. Among lactic acid bacteria, Bifidobacterium longum KACC91563, isolated from fecal samples of healthy Korean neonates, has the capability to alleviate food allergy effects. Operating as a peptide importer, the extracellular OppA receptor from gram-positive B. longum KACC91563 translocates nutrients, specifically peptides, from the outside environment of the intestinal tract to the inside of symbiotic cells. In the present study we attempt to explicate the relationship between the substrate’s specificity from the OppA importer and the probiotic effects of B. longum KACC91563 in the host intestine. It was first identified in this study the specialized structure–function relationship from the OppA importer of B. longum KACC91563 with its structural and functional determinants. This could provide insights into substrate specificity of unique immunological properties and a key switch for the substrate’s metabolism to reprogramming immune responses in the host intestine by structure-based molecular modeling. The probiotic effects of oligopeptide substrate (such as a proline-rich peptide containing at least one branched residue of leucine, isoleucine, and valine) and its metabolism for the OppA from B. longum KACC91563 are attributed to enhancement of the epithelial barrier by several different strain specific pathways to prevent the strong adhesion of pathogens.     

Quantum-dot-labeled DNA probes for fluorescence in situ hybridization (FISH) in the microorganism Escherichia coli.

Semiconductor quantum dots (QDs) as a kind of nonisotopic biological labeling material have many unique fluorescent properties relative to conventional organic dyes and fluorescent proteins, such as composition- and size-dependent absorption and emission, a broad absorption spectrum, photostability, and single-dot sensitivity. These properties make them a promising stable and sensitive label, which can be used for long-term fluorescent tracking and subcellular location of genes and proteins. Here, a simple approach for the construction of QD-labeled DNA probes was developed by attaching thiol-ssDNA to QDs via a metal-thiol bond. The as-prepared QD-labeled DNA probes had high dispersivity, bioactivity, and specificity for hybridization. Based on such a kind of probe with a sequence complementary to multiple clone sites in plasmid pUC18, fluorescence in situ hybridization of the tiny bacterium Escherichia coli has been realized for the first time.     

Synthesis and in Vitro Evaluation of New Cephalosporins Exhibiting Antimicrobial Activity against Gram-Positive Bacteria,in Particular Methicillin-Resistant Staphylococci

The preparation and biological evaluation of 7β-[[2-(phenyl)thiazol-4-yl]acetamido]cephalosporins and 7β-[[(2-(pyridin-2-yl)thiazol-4-yl]acetamido]cephalosporins, 9a-o , substituted at the 3-position with acetyloxymethyl, chlorine, hydrogen, and methyl are described. Hantzsch's thiazole synthesis is employed to provide thiazoleacetic acids 5a-e , subsequently followed by Morpho CDI-assisted amidation to complete the synthesis of target cephalosporins 9a-o . These compounds display activity selectively against Gram-positive bacteria, but are inactive against most Gram-negative bacteria tested. Those with acetyloxymethyl at the 3-position, i.e., 9a, 9e, 9i, 9m , and 90 , exhibit activity with minimal inhibitory concentrations of 16 (μg/mL or lower against four strains of methicillin-resistant staphylococci, namely Staphylococcus aureus X400 and S13E and Staphylococcus epidermidis 270 and 222. Notably, 9a displays an activity profile similar to that of vancomycin regarding its spectrum and potency.