Peptide Utilization by Amino Acid Auxotrophs of Neurospora crassa

The ability of auxotrophs of Neurospora crassa to grow on certain tripeptides, despite the presence of excess competing amino acids, suggests it has an oligopeptide transport system. In general, dipeptides did not support growth except in those instances where extracellular hydrolysis occurred, or where the dipeptide appeared to be accumulated by an uptake system which is sensitive to inhibition by free amino acids. Considerable intracellular peptidase activity toward a large number of peptides was demonstrated, including a number of peptides which could not be utilized for growth. The intracellular peptidase activity was shown to be selective for amino acid composition and sequence (N-terminal or C-terminal) within the peptide; glycine-containing peptides were particularly poor substrates for peptidase activity. Only a small amount of extracellular peptidase activity could be detected.     

Mechanisms of Inhibitory Amino Acid Release in the Brain Stem Under Normal and Ischemic Conditions

This article deals with the release of GABA, glycine and taurine from the brain stem under normal conditions and in ischemia. The release mechanisms, the effects of glutamate and adenosine receptors, and the roles of nitric oxide and second messengers are reviewed.     

Alteration in the Amino Acid Content of Yeast During Growth Under Various Nutritional Conditions

Yeast cells grown under optimal and suboptimal concentrations of biotin were analyzed for the amino acid content of their soluble pool and cellular protein. Optimally grown yeast cells exhibited a maximum amino acid content after 18 hr of growth. Biotin-deficient cells were depleted of all amino acids at 26 and 43 hr, with alanine, arginine, aspartate, cysteine, glutamate, isoleucine, leucine, lysine, methionine, serine, threonine, and valine being present in less than half the concentration observed in biotin-optimal cells. At early time intervals, the amino acid pool of biotin-deficient yeast contained lower concentrations of all amino acids except alanine. After more prolonged incubation, several amino acids accumulated in the pool of biotin-deficient yeast, but citrulline and ornithine accumulated to appreciable levels. The addition of aspartate to the growth medium resulted in a decrease in the amino acid content of biotin-optimal cells but caused a marked increase in the concentration of amino acids in biotin-deficient cells. The pools of biotin-deficient yeast grown in the presence of aspartate displayed a marked reduction in every amino acid with the exception of aspartate itself. These data provide evidence that the amino acid content of yeast cells and their free amino acid pools are markedly affected by biotin deficiency as well as by supplementation with aspartate, indicating that aspartate plays a major role in the nitrogen economy of yeast under both normal as well as abnormal nutritional conditions.     

红树林细菌G1产抗菌活性物质发酵条件的优化

目的:对一株从广西山口红树林保护区筛选得到的具有广谱抗菌活性的红树林细菌G1进行发酵条件的研究.方法:采用单因素实验法对G1产抗菌活性物质的发酵培养基及培养条件进行研究.结果:确定了红树林细菌G1的最佳发酵培养基为:蔗糖2.0％、酵母粉1.5％、NaCl1％.最佳发酵培养条件为:装液量40％、接种量5％、发酵时间84h、初始pH值8.0,优化后G1发酵液的抗菌活性提高了2倍.结论:初步确定了G1发酵的条件,为工业化生产抗菌活性物质提供了理论依据.     

Time-Dependent Lactate Production and Amino Acid Utilization in Cultured Astrocytes Under High Glucose Exposure

Accumulating investigations have focused on the severity of central nervous system (CNS) complications in diabetic patients. The effects of the high glucose (HG) probably attribute to the metabolic disturbances in CNS. Astrocytes, with powerful ability of metabolic regulation, play crucial roles in physiological and pathological processes in CNS. Hence, an in-depth analysis as to metabolic alterations of astrocytes exposure to HG would facilitate to explore the underlying pathogenesis. In this study, the ¹H NMR-based metabonomic approach was performed to characterize the metabolic variations of intracellular metabolites and corresponding culture media in a time-dependent manner. Our results revealed a significant elevation in lactate production and release. Four amino acids, leucine, isoleucine, methionine and tyrosine, were the most important metabolites for utilization. Also, profound disturbances of several metabolic pathways, including osmoregulation, energy metabolism, and cellular biosynthesis were observed. In that sense, the detailed information of astrocyte metabolism under HG exposure provides us a comprehensive understanding of the intrinsic metabolic disorders in CNS during hyperglycemia or diabetes.     

Effects of Varying Nitrogen Sources on Amino Acid Synthesis Costs in Arabidopsis thaliana under Different Light and Carbon-Source Conditions

Plants as sessile organisms cannot escape their environment and have to adapt to any changes in the availability of sunlight and nutrients. The quantification of synthesis costs of metabolites, in terms of consumed energy, is a prerequisite to understand trade-offs arising from energetic limitations. Here, we examine the energy consumption of amino acid synthesis in Arabidopsis thaliana. To quantify these costs in terms of the energy equivalent ATP, we introduce an improved cost measure based on flux balance analysis and apply it to three state-of-the-art metabolic reconstructions to ensure robust results. We present the first systematic in silico analysis of the effect of nitrogen supply (nitrate/ammonium) on individual amino acid synthesis costs as well as of the effect of photoautotrophic and heterotrophic growth conditions, integrating day/night-specific regulation. Our results identify nitrogen supply as a key determinant of amino acid costs, in agreement with experimental evidence. In addition, the association of the determined costs with experimentally observed growth patterns suggests that metabolite synthesis costs are involved in shaping regulation of plant growth. Finally, we find that simultaneous uptake of both nitrogen sources can lead to efficient utilization of energy source, which may be the result of evolutionary optimization.     

Bioconversion of Lithocholic Acid Under Anaerobic Conditions by Pseudomonas sp. Strain NCIB 10590

The biotransformation of lithocholic acid by Pseudomonas sp. strain NCIB 10590 under anaerobic conditions was studied. The major products were identified as androsta-1,4-diene-3,17-dione and 3-oxochol-4-ene-24-oic acid. The minor products included 17β-hydroxyandrost-4-ene-3-one, 17β-hydroxyandrosta-1,4-diene-3-one, 3-oxo-5β-cholan-24-oic acid, 3-oxochola-1,4-diene-24-oic acid, 3-oxopregn-4-ene-20-carboxylic acid, and 3-oxopregna-1,4-diene-20-carboxylic acid. Anaerobiosis increases the number of metabolites produced by Pseudomonas sp. NCIB 10590 from lithocholic acid.     

Tetrazine-Containing Amino Acid for Peptide Modification and Live Cell Labeling

A novel amino acid derivative 3-(4-(1, 2, 4, 5-tetrazine-3-yl) phenyl)-2-aminopropanoic acid was synthesized in this study. The compound possessed better water-solubility and was synthesized more easily compared with the well-known and commercially available 3-(p-benzylamino)-1, 2, 4, 5-tetrazine. Tetrazine-containing amino acid showed excellent stability in biological media and might be used for cancer cell labeling. Moreover, the compound remained relatively stable in 50% TFA/DCM with little decomposition after prolonged exposure at room temperature. The compound could be utilized as phenylalanine or tyrosine analogue in peptide modification, and the tetrazine-containing peptide demonstrated more significant biological activity than that of the parent peptide. The combination of tetrazine group and amino acid offered broad development prospects of the bioorthogonal labeling and peptide synthesis.     

Effects of Hydrophobic Amino Acid Substitutions on Antimicrobial Peptide Behavior

Antimicrobial peptides (AMPs) are naturally occurring components of the immune system that act against bacteria in a variety of organisms throughout the evolutionary hierarchy. There have been many studies focused on the activity of AMPs using biophysical and microbiological techniques; however, a clear and predictive mechanism toward determining if a peptide will exhibit antimicrobial activity is still elusive, in addition to the fact that the mechanism of action of AMPs has been shown to vary between peptides, targets, and experimental conditions. Nonetheless, the majority of AMPs contain hydrophobic amino acids to facilitate partitioning into bacterial membranes and a net cationic charge to promote selective binding to the anionic surfaces of bacteria over the zwitterionic host cell surfaces. This study explores the role of hydrophobic amino acids using the peptide C18G as a model system. These changes were evaluated for the effects on antimicrobial activity, peptide-lipid interactions using Trp fluorescence spectroscopy, peptide secondary structure formation, and bacterial membrane permeabilization. The results show that while secondary structure formation was not significantly impacted by the substitutions, antibacterial activity and binding to model lipid membranes were well correlated. The variants containing Leu or Phe as the sole hydrophobic groups bound bilayers with highest affinity and were most effective at inhibiting bacterial growth. Peptides with Ile exhibited intermediate behavior while those with Val or α-aminoisobutyric acid (Aib) showed poor binding and activity. The Leu, Phe, and Ile peptides demonstrated a clear preference for anionic bilayers, exhibiting significant emission spectrum shifts upon binding. Similarly, the Leu, Phe, and Ile peptides demonstrated greater ability to disrupt lipid vesicles and bacterial membranes. In total, the data indicate that hydrophobic moieties in the AMP sequence play a significant role in the binding and ability of the peptide to exhibit antibacterial activity.     

辣椒枯萎病拮抗细菌Ljb002菌株发酵条件的优化

从辣椒根际分离筛选到1株具有较强促生能力但拮抗能力一般的细菌菌株Ljb002,为提高抑制辣椒枯萎病病原菌孢子的萌发能力,采用响应面分析方法（Response Surface Methodology,RSM）对该菌株的液体发酵条件进行优化。在单因素的基础上利用Plackett-Burman设计方法对8种影响因素进行了重要性评价。结果表明,初始pH、蛋白胨和MgSO₄加入量对菌株Ljb002发酵液抑制孢子萌发的能力有显著影响。采用响应面分析方法对这3个主要因素进行优化,优化的最佳条件组成为初始pH 7.72、蛋白胨12.93 g/L、硫酸镁1.98 g/L、葡萄糖20 g/L、接种量3%、种龄10 h、100 mL三角瓶装液量为14 mL、培养温度28 ℃,此时相对孢子萌发抑制率最大为96.73%。在验证试验中相对孢子萌发抑制率达到了95.18%,与优化前相对孢子萌发抑制率64.37%相比提高了32.37%。     

不同肝脏疾病患者血浆游离氨基酸水平改变的模式

采用DNS -Cl荧光标记氨基酸 ,聚酰胺薄膜层析 ,分析了慢性血吸虫病肝肿大、晚期血吸虫病肝肿大 ,慢活肝 ,慢迁肝以及肝硬化等五种不同肝损伤患者血浆游离氨基酸水平 ,结果发现它们血浆游离氨基酸改变 ,均有一定的特异的模式     

Modeling Natural Attenuation of Chlorinated Ethenes Under Spatially Varying Redox Conditions

A three-dimensional model for the transport and reductive dechlorination of chlorinated ethenes in ground-water systems with variable redox conditions is demonstrated and applied to a pilot test for accelerated natural attenuation of trichloroethene (TCE). The rate and extent of biotransformation of TCE and chlorinated progeny is controlled by the dominant terminal electron accepting process (TEAP) that is simulated over space and time. The solute transport code, Sequential Electron Acceptor Model, 3D-transport, (SEAM3D) which simulates aerobic and sequential anaerobic biodegradation of organic carbon, is modified to implement the equations. Results of a generic model for TCE transport in ground-water systems with different redox conditions demonstrate that the degree of chlorinated ethene attenuation is influenced by background concentrations of aqueous- and solid-phase electron acceptors, but that model results are sensitive to other input parameters (inhibition coefficients, maximum rate of reductive dechlorination, biomass concentrations, and ground-water velocity). Simulation results of enhanced in situ bioremediation using dissolved organic carbon as a reducing agent show that spatial and temporal changes in the dominant TEAP and the subsequent rate of reductive dechlorination are adequately represented with the model. Initial concentrations of Fe(III) and the dechlorinating microbial population influence the simulated time lag observed during the pilot test.     

Element Stoichiometry of a Mixotrophic Protist Grown Under Varying Resource Conditions

ABSTRACT. The balance of essential elements (e.g. carbon [C], nitrogen [N], and phosphorus [P]) between consumers and their resources influences not only the growth and reproduction of the consumers but also the nutrients they regenerate. Flagellate protists are significant predators of aquatic bacteria and directly influence nutrient flow to higher trophic levels and, through excretion, influence the mineral element composition of dissolved nutrients. Because the element stoichiometry of protists is poorly characterized, we varied the resource composition of the bacterium Pseudomonas fluorescens and used it to grow the mixotrophic bacterivorous flagellate Ochromonas danica. Using a mass balance approach, the element composition of O. danica was found to vary depending upon the nutrient composition of the prey and ranged between 482:36:1 and 80:12:1 (C:N:P molar). Homeostasis plots suggested that flagellate protists weakly regulate their element composition and are likely to regenerate different elements depending upon the nature of the element limiting growth of their prey.     

光合细菌PSB-1菌株的分离鉴定及其生物学特性的研究

光合细菌菌株ＰＳＢ－１,初步定为Ｒｈｏｄｏｐｓｅｕｄｏｍｏｎａｓ ａｃｉｄｏｐｈｉｌａ,系由生活污水中分离获得,革兰氏反应阴性,菌体大小为：长０．２５～０．４５μｍ,宽０．８～２．０μｍ,单个细胞卵圆至球形,出芽生殖,未观察到鞭毛。菌落为玫瑰红色,菌体液体培养物为深红色,菌体中含有丰富的细菌叶绿素ａ和类胡萝卜素,光合内膜结构为片层状,位于质膜之下并与质膜平行。ＰＳＢ－１在黑暗和光照中均能生长,但在黑暗中培养时菌液颜色不变,能利用多种有机碳源和氮源,ＤＮＡ中Ｇ＋Ｃ摩尔分数为６５．７％。     

海洋细菌9912肽抗生素发酵条件优化研究

对海洋细菌 9912肽抗生素发酵培养基及培养条件进行了研究。结果表明 ,采用廉价的玉米粉、豆饼粉和葡萄糖即可得到良好的效果 ,比实验室培养基提高效价 11%。培养条件为 2 8℃ ,种龄 12h ,接种量 5 % ,发酵周期 2 0h。     

Analysis of the Preserved Amino Acid Bias in Peptide Profiles of Iron Age Teeth from a Tropical Environment Enable Sexing of Individuals Using Amelogenin MRM

The first dental proteomic profile of Iron Age individuals (ca. 2000–1000 years B.P.), collected from the site of Long Long Rak rock shelter in northwest Thailand is described. A bias toward the preservation of the positively charged aromatic, and polar amino acids is observed. It is evident that the 212 proteins identified (2 peptide, FDR <1%) comprise a palimpsest of alterations that occurred both ante‐mortem and post‐mortem. Conservation of amino acids within the taphonomically resistant crystalline matrix enabled the identification of both X and Y chromosome linked amelogenin peptides. A novel multiple reaction monitoring method using the sex specific amelogenin protein isoforms is described and indicate the teeth are of male origin. Functional analysis shows an enrichment of pathways associated with metabolic disorders and shows a capacity for harboring these conditions prior to death. Stable isotope analysis using carbon isotopes highlights the strongly C₃ based (≈80%) diet of the Long Long Rak cemetery people, which probably comprised rice combined with protein from freshwater fish among other food items. The combination of proteomics and stable isotope analysis provides a complementary strategy for assessing the demography, diet, lifestyle, and possible diseases experienced by ancient populations.     

一株DDT降解菌的筛选、鉴定及降解特性的初步研究

从DDT污染的土壤中筛选具有DDT降解能力的细菌,经过富集培养、分离纯化得到56株细菌,将其接种到基础盐酵母培养基,7d后用紫外分光光度计法初筛得到降解率较高的一株菌,编号为D-1.通过16S rDNA序列分析结合传统分类学方法确定该菌为寡养单胞菌属(Stenotrophomonas sp.)的一株茵.对菌体降解DDT的特性的研究表明,在培养温度为3℃,底物质量浓度为40 mg/L, pH 7.0,摇床转速为200 r/min的条件下,该菌株对DDT降解10d的降解率为69.0%.     

一株DDT降解菌的筛选、鉴定及降解特性的初步研究

从DDT污染的土壤中筛选具有DDT降解能力的细菌, 经过富集培养、分离纯化得到56株细菌, 将其接种到基础盐酵母培养基, 7 d后用紫外分光光度计法初筛得到降解率较高的一株菌, 编号为D-1。通过16S rDNA序列分析结合传统分类学方法确定该菌为寡养单胞菌属(Stenotrophomonas sp.)的一株菌。对菌体降解DDT的特性的研究表明, 在培养温度为30℃, 底物质量浓度为40 mg/L, pH 7.0, 摇床转速为200 r/min的条件下, 该菌株对DDT降解10 d的降解率为69.0%。     

Survival of Mayfly Larvae Under Mine Acid Conditions

Mayfly larvae were abundant and diverse in riffle zones of three control streams in southeastern Ohio. But none were found in such zones of three streams having current or past histories of mine acid pollution, despite vegetative recovery of reclaimed land bordering two of the streams. Laboratory studies showed stepwise increases in non-predatory mortality of mayfly larvae with increased mine acidity. Dragonfly larvae predation on mayfly larvae was constant at pH 8.1–4.1, but decreased at pH 3.1 despite tolerance of dragonfly larvae to low pH conditions. Extensive acid mine pollution thus may threaten aquatic biota through removal of food sources or reduced feeding rates as well as through direct mortality.