Detoxification of environmental sulfide to sulfane sulfur in the intertidal sipunculid Phascolosoma arcuatum

The capability of Phascolosoma arcuatum to detoxify sulfide in anaerobic conditions was examined. Sulfane sulfur, which underwent cold cyanolysis, was the major excretory end product of sulfide detoxification during anoxia. Thiosulfate was not excreted into the external medium. Instead, it was absorbed by P. arcuatum and its absorption was stimulated by the presence of sodium sulfide (Na₂S) in the incubation medium. The effective formation and excretion of sulfane sulfur by P.␣arcuatum required the presence of both Na₂S and sodium thiosulfate (Na₂S₂O₃). Results obtained indicate that rhodanese might be involved in sulfide detoxification in this sipunculid. Rhodanese could act as a catalyst in the transfer of sulfur atoms from thiosulfate to HS⁻. The body wall and the introvert were the main sites of sulfide detoxification. However, it is unlikely that epibiotic bacteria associated with the outside surface of the worm were involved in the detoxification process. A time-course study on the contents of thiosulfate and sulfane sulfur in the body wall of P. arcuatum incubated anaerobically in the presence of Na₂S + Na₂S₂O₃ verified that thiosulfate absorbed was utilized to detoxify sulfide to sulfane sulfur. Accepted: 24 October 1996     

Regulatory mechanism of contraction in the proboscis retractor muscle of a sipunculid worm,Phascolosoma scolops

Summary Regulatory mechanism of contraction in the proboscis retractor muscle of Phascolosoma scolops was studied by physiological measurements and cytochemical electron microscopy. The magnitude of K⁺-contracture was dependent on external Ca²⁺ concentration and the contracture disappeared in Ca²⁺-free solution. The K⁺-contracture was suppressed by application of procaine and Mn²⁺. Caffeine induced contracture even when external Ca²⁺ was absent. Ultrastructural observations of the retractor muscle cells showed the presence of a large number of vesicles (subsarcolemmal vesicles), corresponding to the sarcoplasmic reticulum in vertebrate skeletal muscle, underneath the plasma membrane. For the cytochemical electron microscopy, the muscle fibers were fixed with 1% OsO₄ solution containing 2% K-pyroantimonate. In the relaxed fibers, pyroantimonate precipitates were localized along the inner surface of plasma membrane and in the subsarcolemmal vesicles. In the contracting fibers, the precipitates were uniformly distributed in the myoplasm. The X-ray microanalysis revealed that the precipitates contained Ca. These results suggest that the contractile system is activated by the influx of extracellular Ca²⁺ as well as by the release of Ca²⁺ from the intracellular structures such as the inner surface of the plasma membrane and subsarcolemmal vesicles.     

A relationship between free amino acid and nickel contents in leaves and seeds ofAlyssum bertolonii

Summary Data are given on the aqueous acetone—soluble (free) amino acid composition and total nickel contents of leaves of wild and cultivatedAlyssum bertolonii and of seeds produced by the former. Leaves of the wild plants show a direct relationship between their total free amino acid N and Ni contents. These are highest in February, show a decrease in June and increase again by October. It is inferred that variations in the Ni uptake and free amino acid contents are functions of seasonal factors. Leaves of cultivated plants showed the lowest Ni content but the highest free amino acid content illustrating the influence of environmental factors.     

Some physiological functions of the L-leucine dehydrogenase in Bacillus subtilis

Mutants of Bacillus subtilis constitutive for L-leucine dehydrogenase synthesis were selected. Using these mutants we could determine two functional roles for the L-leucine dehydrogenase. This enzyme liberates ammonium ions from branched chain amino acids when supplied as the sole nitrogen source. Another function is to synthesize from L-isoleucine, L-leucine, and L-valine the branched chain -keto acids which are precursors of branched chain fatty acid biosynthesis. These results together with the inducibility of the enzyme suggest that the L-leucine dehydrogenase has primarily a catabolic rather than an anabolic function in the metabolism of Bacillus subtilis.     

The habitat and conduit functions of roads in the spread of three invasive plant species

Nonnative plant species commonly occur along roadsides, and populations are often assumed to invade by spread along the road axis. To distinguish between the function of roadsides as movement corridors and as habitat, nonnative plant species were surveyed along roads in deciduous forest sites in southeastern Ohio, USA. The importance of road proximity was tested by comparing nonnative species abundance in 100 m transects along roads with transects in undisturbed forest. Nonnative species were most abundant and most frequently observed in roadside sites in valleys. Three common species were chosen for closer scrutiny. In a seed sowing experiment roads and open sites proved to be better locations for the germination and growth of Microstegium vimineum than non-roadside and closed-canopy sites. Tussilago farfara and Rosa multiflora occurred in a small number of disjunct patches suggesting infrequent arrival in the sampled transects. Both species were strongly clustered at scales consistent with diffusive spread by vegetative growth and short-range seed dispersal. Comparisons of distributions parallel and perpendicular to roads showed no evidence for enhanced dispersal along the road axis. Microstegium distributions were correlated with local light availability implying site saturation. Microstegium micro-distributions suggested that spread along the road axis was facilitated by movement of dormant seeds in road maintenance. Thus, roadsides appear to function as both habitat and a conduit for population expansion, with the rate of spread dependent on the life history of the individual species. These results suggest a hierarchical process of regional invasion, with different dispersal mechanisms functioning at different spatial scales.     

Occurrence of a unique amino acid racemase in a basidiomycetous mushroom, Lentinus edodes

Free -alanine was detected in a cell extract of the fruit-body of an edible basidiomycetous mushroom, Lentinus edodes (Shiitake), by means of reverse-phase high performance liquid chromatography. We also found an amino acid racemase activity in L. edodes fruit-body, and purified the enzyme. The enzyme has a molecular weight of approximately 86,000, and consists of two subunits of identical molecular weight (44,000). The optimal pH of the enzyme activity is around pH 9.5 for both -to- and -to- alanine racemization. The enzyme requires pyridoxal 5′-phosphate as a cofactor. K_m and V_max values for -alanine were 37.3 mM and 520 nmol/min/mg, respectively; for -alanine, they were 9.21 mM and 141 nmol/min/mg, respectively. The equilibrium constant was calculated to be 1.10, which is consistent with the theoretical value for the racemase reaction. The ability of the enzyme to catalyze the racemization of various -amino acids was investigated. The enzyme catalyzes the racemization of -serine (relative reaction rate, 144% of rate for -alanine), -alanine (100%), -homoserine (17.1%), -2-aminobutyrate (5.6%), -glutamate (4.5%), and -asparagine (3.2%). To the best of our knowledge, this is the first report of an amino acid racemase produced by a basidiomycetous mushroom.     

木豆不同品种和叶龄对叶片氨基酸形成的影响和聚类分析

为了解木豆(Cajanus cajan)叶片的氨基酸含量的变化,对19份种质资源和1～3叶龄的木豆叶片氨基酸含量进行研究。结果表明,不同种质资源和叶龄的木豆叶片中均含有17种氨基酸,必需氨基酸以苏氨酸、异亮氨酸和赖氨酸的含量最高,分别为0.67%、0.70%和0.48%,非必需氨基酸以丝氨酸、酪氨酸和组氨酸的含量最高,分别为0.69%、0.66%和0.44%。除赖氨酸和丙氨酸外,其余15种氨基酸含量在木豆叶片中总体上随着叶龄的增加呈现上升趋势。不同种质资源的木豆叶片中总氨基酸含量差异明显。聚类分析可将19个木豆种质资源划分为低氨基酸型(I)、中氨基酸型(II)、中高氨基酸型(III)、高氨基酸型(IV)等4大类型。这为高品质木豆叶茶的加工与高氨基酸木豆品种选育提供了理论依据。     

Expression of a ferredoxin-dependent glutamate synthase gene in mesophyll and vascular cells and functions of the enzyme in ammonium assimilation in Nicotiana tabacum (L.)

GLU1 encodes the major ferredoxin-dependent glutamate synthase (Fd-GOGAT, EC 1.4.7.1) in Arabidopsis thaliana (ecotype Columbia). With the aim of providing clues on the role of Fd-GOGAT, we analyzed the expression of Fd-GOGAT in tobacco (Nicotiana tabacum L. cv. Xanthi). The 5′ flanking element of GLU1 directed the expression of the uidA reporter gene in the palisade and spongy parenchyma of mesophyll, in the phloem cells of vascular tissue and in the roots of tobacco. White light, red light or sucrose induced GUS expression in the dark-grown seedlings in a pattern similar to the GLU1 mRNA accumulation in Arabidopsis. The levels of GLU2 mRNA encoding the second Fd-GOGAT and NADH-glutamate synthase (NADH-GOGAT, EC 1.4.1.14) were not affected by light. Both in the light and in darkness, ¹⁵NH₄⁺ was incorporated into [5−¹⁵N]glutamine and [2−¹⁵N]glutamate by glutamine synthetase (GS, EC 6.3.1.2) and Fd-GOGAT in leaf disks of transgenic tobacco expressing antisense Fd-GOGAT mRNA and in wild-type tobacco. In the light, low level of Fd-glutamate synthase limited the [2−¹⁵N]glutamate synthesis in transgenic leaf disks. The efficient dark labeling of [2−¹⁵N]glutamate in the antisense transgenic tobacco leaves indicates that the remaining Fd-GOGAT (15–20% of the wild-type activity) was not the main limiting factor in the dark ammonium assimilation. The antisense tobacco under high CO₂ contained glutamine, glutamate, asparagine and aspartate as the bulk of the nitrogen carriers in leaves (62.5%), roots (69.9%) and phloem exudates (53.2%). The levels of glutamate, asparagine and aspartate in the transgenic phloem exudates were similar to the wild-type levels while the glutamine level increased. The proportion of these amino acids remained unchanged in the roots of the transgenic plants. Expression of GLU1 in mesophyll cells implies that Fd-GOGAT assimilates photorespiratory and primary ammonium. GLU1 expression in vascular cells indicates that Fd-GOGAT provides amino acids for nitrogen translocation. The nucleotide sequence data of the GLU1 gene reported in the present study is available from GenBank with the following accession number: AY189525     

D- and L-Aspartic Acids: New Non-sugar Components of Bacterial Polysaccharides

For the first time in bacterial polysaccharides, residues of D- and L-aspartic acids were identified as N-acyl substituents of 4-amino-4,6-dideoxy-D-glucose in the O-antigens of enterobacteria of the genera Providencia and Proteus.     

Effects of starvation and - or -alanine administration on the free - and -alanine levels in the muscle and hepatopancreas of the crayfish, Procambarus clarkii

Changes of - and -alanine and other free amino acids were examined in muscle and hepatopancreas of the crayfish Procambarus clarkii before and after a 1-month starvation in freshwater, 50% seawater, and seawater. Total free amino acids and - and -alanine in both tissues decreased during starvation. The largest decrease was found in the animals starved in freshwater. In 50% seawater and full-strength seawater, the ratio of -alanine to total alanine increased in both tissues, although the level was reduced a little. A large dose of -alanine administered into the tail muscle of freshwater crayfish was converted to -alanine and -alanine returned to the control level within a week. A large amount of -alanine was transported from muscle to hepatopancreas. -Alanine injected into freshwater crayfish was converted to -alanine, but was not transported to the hepatopancreas. In the case of -alanine injection into the muscle of crayfish acclimated to 50% seawater, large amounts of - and -alanine were maintained in the muscle during the experimental period of 4 days. These data indicate that -alanine is metabolized actively in crayfish tissues and accumulated as an important osmolyte during osmotic stress.     

Radioimmunoassay for the determination of free and conjugated abscisic acid

The characterization and application of a radioimmunoassay specific for free and conjugated abscisic acid (ABA) is reported. The antibodies produced against a bovine serum albumin-(±)-ABA conjugate have a high affinity for ABA (K_a=1.3x10⁹l mol^-1). Trans, trans-ABA and related compounds, such as xanthoxin, phaseic acid, dihydrophaseic acid, vomifoliol or violaxanthin do not interfere with the assay. The detection limit of this method is 0.25x10^-12 mol ABA, the measuring range extends to 20x10^-12 mol, and average recoveries are 103%. Because of the high specificity of this immunoassay, no extract purification steps are required prior to analysis. Several hundred plants can be analyzed per day in a semi-automatic assay performance. ABA has been detected in all higher plant families examined, but was absent in the blue-green alga, Spirulina platensis, the liverwort Marchantia polymorpha, and two species of fungi.Abbreviations ABA abscisic acid - BHT 2.6-di-t-butyl-4-methyl phenol - TLC thin-layer chromatography - HSA human serum albumin Part 7 in the Series: Use of Immunoassay in Plant Science     

Morphological and physiological traits of three major Arabidopsis thaliana accessions

Arabidopsis is currently the most studied organism in plant biology. Its short life cycle and small genome size have rendered it one of the principal model systems. Additionally, numerous large T-DNA insertion mutant collections are available. The advent of molecular biology and the completion of the Arabidopsis genome sequence have contributed to helping researchers discover a large variety of mutants identified for their phenotypes. Yet, it is important to consider that natural phenotypic variations exist and appear in natural ecotypes, differing greatly in several traits. Although there are a vast number of ecotypes available, only a few have been extensively studied, and some have been created in laboratories. In order to identify new phenotypic differences, we chose to study the differences observed between three ecotypes: Columbia (Col-0), Landsberg erecta (Laer-0) and Wassilewskija (Ws-0). Our research focuses on observable morphological traits throughout plant growth and development along the entire plant life cycle. We then attempted to shed some light on phenotypic discrepancies through the study of the class III peroxidase protein family, which is involved in many aspects of plant growth and tissue differentiation. Both morphological and molecular aspects reveal that there are major variations between ecotypes, hence indicating a possibly interesting heterotic effect in the F1 from crosses between different Arabidopsis ecotypes.     

Investigation of the physiological properties and synthesis of PUFAs from Thraustochytrids and its electrophoretic karyotypes

Physiological properties of organism, such as the number of chromosomes, genome size, fatty acid profile and the activities of desaturases and elongases were investigated for four differentThraustochytrium species. The investigation revealed thatThraustochytrium aureum could synthesize a significant level of polyunsaturated fatty acids (PUFAs), particularly docosa-hexaenoic acid (DHA), when compared to the other threeThraustochytrium species tested. A higher level of saturated fatty acids was observed byT. striatum followed byThraustochytrium sp. ATCC 26185. The PUFA accumulation rate was higher in the n-3 than in the n-6 pathway. A comparison of the activities for these desaturases and elongases of the four different species were also studied. Further, the electrophoretic karyotypes of Thraustochytrids were separated by pulsed-field gel electrophoresis (PFGE). The separation condition of PFGE was developed to obtain the different chromosomes from the variousThraustochytrium species. The number of chromosomes inT. aureum, T. striatum, Thraustochytrium sp. ATCC 20891 andThraustochytrium sp. ATCC 26185 were 13, 17, 10. 8, and the whole genome size of those species were estimated to be 12.9, 11.7, 11.3 and 9.93 Mbp, respectively.     

Responses of the African Armyworm and three species of borers to carbohydrates and phenolic substances: an electro- and behavioural physiological study

Electrophysiological recordings were made from the maxillary sensilla styloconica of fifth instars of the African Armyworm, Spodoptera exempta (Wlk.) (Lep.: Noctuidae), and the borers (Lep.: Pyralidae) Eldana saccharina Wlk. and Maruca testulalis (Geyer), and fifth and sixth instars of the borer Chilo partellus (Swinhoe). Stimuli were different concentrations of 13 carbohydrates and 11 phenolic substances. It appeared that a sucrose sensitive cell is present in the lateral styloconic sensilla of Spodoptera, Maruca and Chilo, and in both the lateral and medial sensilla of Eldana. The sucrose cell of fifth-instar Chilo is more sensitive than that of sixth instars. The additional responses of the medial cells to the phagostimulant sucrose are supposed to have contributed to the widespread infestation of sugarcane by Eldana. The medial sensilla of the Armyworm contain a cell type responding to both meso-inositol and D-ribose. Chilo appeared to be the only one of the three borer species able to perceive phenolic substances. It has a cell responsive to chlorogenic acid in its medial sensilla, which is a bit more sensitive in fifth- than in sixth-instar larvae. The presence of this cell may account for the positive correlation between total phenols content and resistance of sorghum cultivars to this borer. Spodoptera can perceive four phenolic acids. Its lateral sensilla contain a cell responsive to chlorogenic acid and its medial sensilla a cell responsive to 4-hydroxybenzoic acid, gallic acid as well as vanillic acid. Feeding experiments showed that the latter substances inhibit feeding in the Armyworm.So far, in the borers adequate stimuli could be determined for only tow or three of the four taste cells present in each sensillum styloconicum. This indicates that we are still unaware of chemicals that may be important to these caterpillars. On the other hand, for the sensilla styloconica of Spodoptera, electrophysiology suggests the presence of five or six taste cell types, whereas only four taste cells are known from morphological studies.     

五株乳酸菌和三株芽孢杆菌的生物学特性和功能

【背景】乳酸菌和芽孢杆菌是应用于生产最多的益生菌,但不同菌株间的生长特性均不相同,因此了解菌株的生物学特性具有重要意义。【目的】研究菌株的生物学特性,能合理地开发和利用菌株,以保证菌株生产应用的安全性。【方法】活化后鉴定5株乳酸菌和3株芽孢杆菌并对其形态进行观察,探究菌株的生长曲线、产酸能力及最适生长条件,测定菌株的抑菌活性和产酶性能,同时探究菌株的益生性和安全性。【结果】五株乳酸菌分别编号鉴定为干酪乳杆菌R1、副干酪乳杆菌R2、香肠乳杆菌R3、福莱乳杆菌R4和唾液乳杆菌R5;3株芽孢杆菌分别编号命名为贝莱斯芽孢杆菌Y1、枯草芽孢杆菌Y2和地衣芽孢杆菌Y3。八株菌形态结构均不相同但都为杆状,均在2–10 h为对数生长期,18–24 h为稳定期,培养24 h时乳酸菌和芽孢杆菌的活菌数均保持在10⁹和10⁸ CFU/mL,最适生长温度为37.0℃。乳酸菌具有较强的产酸能力和抑菌活性,芽孢杆菌有较强的产酶性,在人工胃液中都有较强的耐受性。八株菌都无溶血活性、无毒力基因、对抗生素都保持中度敏感以上;其中唾液乳杆菌有四环素耐药基因,但对四环素抗性为中度敏感。【结论】八株菌生长繁殖速度快,乳酸菌产酸能力和抑菌活性较强,芽孢杆菌具有较强的产酶性能,在体外具有较好的益生性和安全性,可应用于生产实践。     

莲的生物活性成分及生理功能研究进展

莲（Nelumbo nucifera Gaertn.）是莲科莲属（Nelumbo）的多年水生双子叶草本植物,在中国湖北、江苏、安徽、江西、湖南、浙江等地区大量种植。研究表明,莲不同部位含有大量生物活性成分,包括多酚类、生物碱、多糖类、膳食纤维、维生素、氨基酸及多种微量元素。从莲中提取的生物活性成分具有多种生理功能,如抗炎、抗氧化、抗衰老、抗肿瘤、降血糖、降血脂、减肥、护肝、护肾、促进睡眠、免疫调节、治疗阿尔茨海默病、抗病毒、缓解抑郁症等。综述了近年来国内外对莲不同部位的生物活性成分以及其生理功能的最新研究进展,旨在为深入挖掘莲药用价值提供理论参考。     

不同生态型芦苇种群对盐胁迫的生长和光合特性

土壤盐渍化是影响我国土壤利用效率的主要因素之一,芦苇是改良土壤盐渍化的良好实验材料,但芦苇有着多种的生态型,比较各生态型芦苇的耐盐差异成为亟待解决的问题。通过设置淡水(0.00%)与加盐(质量浓度2.00%)处理控制实验,测量芦苇的生长指标和光合指标,比较河口型芦苇与内陆型芦苇耐盐性,寻找合适生态型的芦苇作为改良土壤盐渍化的生物材料。在实验中,与淡水条件相比,加盐(2.00%)处理条件下,河口型芦苇和内陆型芦苇的株高(height)、蒸腾速率(E)均显著性下降,但是两种生态型的芦苇的水分利用效率(WUE)明显提高;河口型的芦苇相对生长速率(RGR)和气孔导度(Gs)都明显高于内陆型芦苇。在淡水环境中,河口型芦苇的相对生长速率(RGR)和净光合速率(A)都显著性地高于内陆型芦苇。结果表明两种生态型的芦苇在进化过程中存在一定程度上的分化,盐胁迫会抑制两种芦苇的生长,两种生态型芦苇的相对生长速率和气孔导度在盐胁迫下出现明显地差异,表明两种生态型的芦苇对盐度的响应机制有所差异。相比于内陆型芦苇,河口型芦苇有着更强的耐盐性,内陆型及河口型芦苇的表型性状差异主要是由于其原生境的差异所决定的。     

Regulation of Metabolic and Electron Transport Pathways in the Freshwater Bacterium Beggiatoa leptomitiformis D-402

The biomass yield of freshwater filamentous sulfur bacteria of the genus Beggiatoa, when grown lithoheterotrophically or mixotrophically, has been shown to increase 2 to 2.5 times under microaerobic conditions (0.12 mg/l oxygen) as compared to aerobic conditions (9 mg/l oxygen). The activity of the glyoxylate cycle key enzymes have been found to increase two to three times under microaerobic conditions (at an O₂ concentration of 2 mg/l), and the activities of the sulfur metabolism enzymes increased three to five times (at an O₂ concentration of 0.1–0.5 mg/l). It has also been found that, under microaerobic conditions, thiosulfate was almost completely oxidized to sulfate by the bacteria, without accumulation of intermediate metabolites. At the same time, a 2- to 15-fold decrease in the activities of the tricarboxylic acid cycle enzymes involved in the reduction of NAD and FAD was observed. Reorganization of the respiratory chain after changes in aeration and type of nutrition was also observed. It has been found that, in cells grown heterotrophically, the terminal part of the respiratory chain contained an aa ₃-type oxidase, whereas, during mixotrophic, lithoheterotrophic, and autotrophic growth, aa ₃-type oxidase synthesis was inhibited, and the synthesis of a cbb ₃-type oxidase, which is induced under microaerobic conditions, was activated. The gene of the catalytic subunit CcoN of the cbb ₃-type oxidase was sequenced and proved to be highly homologous to the corresponding genes of other proteobacteria.__________Translated from Mikrobiologiya, Vol. 74, No. 4, 2005, pp. 452–459.Original Russian Text Copyright © 2005 by Muntyan, Grabovich, Patritskaya, Dubinina.     

Synthesis of polyhydroxy amino acids based on D- and L-alanine from D-glycero-D-gulo-heptono-1,4-lactone

2-Amino-2,3-dideoxy-D-manno-heptonic acid (7) has been synthesized from 2,5,6,7-tetra-O-acetyl-3-deoxy-D-gluco-heptono-1,4-lactone (1), which was readily prepared from D-glycero-D-gulo-heptono-1,4-lactone. O-Deacetylation of 1 followed by treatment with 13:1 (v/v) 2,2-dimethoxypropane/acetone in the presence of p-toluenesulfonic acid gave methyl 3-deoxy-4,5:6,7-di-O-isopropylidene-D-gluco-heptonate (3) as a crystalline product (80% yield). The free hydroxyl group (OH-2) of 3 was mesylated and substituted by azide to give the corresponding azide derivative 5. Hydrogenolysis and further hydrolysis of the ester function of 5 afforded alpha-amino acid 7 (43% overall yield from 1). Compound 7 is an analog of L-alanine having a polyhydroxy chain attached to C-3. The diastereoisomer of 7 at C-2, 2-amino-2,3-dideoxy-D-gluco-heptonic acid (12) was also prepared from 3, by a route that involved 2,3-dideoxy-2-iodo derivative 8 as a key intermediate.