Further observations of transport within paddle cilia

Summary Rhabdopleura has densely ciliated tentacles and cephalic shield. These cilia are of two sorts, ordinary cilia and those bearing paddle-like swellings. These swellings, about l m across, are in the ciliary membrane. The axoneme bundle within the cilium remains intact, keeping the usual spatial arrangements, except that in the swelling its overall diameter is reduced. It is suggested that the mechanism for moving the paddle-like swellings along the length of the cilium is the releasing and reattaching of the side filaments from the axoneme to the ciliary membrane. Acknowledgements. I wish to thank the Director and staff of the Plymouth Marine Biological Association for their help and facilities while collecting the material. Mr. R.F. Moss gave much skilled technical assistance. I wish also to thank Professor W.E. Knight-Jones who identified the specimens of Vermiliopsis and Dodecacera.     

Keratin-like fibres in the hemichordate Rhabdopleura compacta

Summary The coenecium of Rhabdopleura is a tube that surrounds the zooid. It is secreted by the cephalic shield of the zooid and contains three sorts of fibres in an electron lucent matrix. One of the fibre types contains a double helix of fine fibrils. Preliminary histochemical investigations suggest that the fibres may be keratinous.I wish to thank Professor J. Z. Young F.R.S. for enthusiastic advice and encouragement. Dr. R. Bellairs generously provided the facilities for electron microscopy. Dr. A. J. Southward and Dr. A. Stebbing of the Plymouth Marine Biological Laboratory generously gave of their time and expertise, and helped me to obtain and identify the specimens. Dr. R. Willis and Miss Marion Dennison assisted with the preliminary stereoscopic electron microscopy. Mr. R. Moss gave excellent technical and photographic assistance.     

Some features of the ultrastructure of the coenecium of Rhabdopleura compacta

Summary The coenecium of Rhabdopleura consists of a series of tubes, some erect and some repent. These tubes are composed of rings, one stacked within another. The rings are smooth on the inside surface and rough outside. Newly laid down rings are thin and smooth on both surfaces, fibrous material is laid down on the external surface during growth in thickness by the cephalic shield of the zooid. The erect tubes remain discrete, but the repent tubes, which are attached to the substratum can become incorporated in a mass of secreted material. The external vertical fibres cross several rings and probably serve to anchor the stack. Besides these fibrils that run for several segments, there are other shorter fibres that run along the length of each cylindrical ring, and are not continuous across the rings. These long and short fibres have features in common with those found in the graptolites.I wish to thank Dr. A. Boyde for scanning electron microscope facilities and for making his expertise so freely available. Dr. A. Stebbing helped me to obtain the specimens. Mrs. E. Bailey and Mr. R. Moss ably provided the technical and photographic assistance     

Revision of the puella group of the genus Coenagrion Kirby, 1890 (Odonata,Zygoptera), with emphasis on morphologies contributing to reproductive isolation

The puella group of the zygopteran genus Coenagrion Kirby, 1890 is revised. The group, as treated here, includes C. puella (L., 1758), C. syriacum (Morton, 1924), C. ponticum (Bartenef, 1929) and C. intermedium (Lohmann, 1990). All four species are redescribed on the basis of a scanning electron microscopical (S.E.M.) analysis of morphological characters involved in copulation. Full species rank is attributed to intermedium. A key to males and females of the four species is included. Reproductive isolation is discussed in the genus Coenagrion.     

A transporter of<Emphasis Type="Italic"> Escherichia coli</Emphasis> specific for<Emphasis Type="SmallCaps"> l</Emphasis>- and<Emphasis Type="SmallCaps"> d</Emphasis>-methionine is the prototype for a new family within the ABC superfamily

An ABC-type transporter in Escherichia coli that transports both l- and d-methionine, but not other natural amino acids, was identified. This system is the first functionally characterized member of a novel family of bacterial permeases within the ABC superfamily. This family was designated the methionine uptake transporter (MUT) family (TC #3.A.1.23). The proteins that comprise the transporters of this family were analyzed phylogenetically, revealing the probable existence of several sequence-divergent primordial paralogues, no more than two of which have been transmitted to any currently sequenced organism. In addition, MetJ, the pleiotropic methionine repressor protein, was shown to negatively control expression of the operon encoding the ABC-type methionine uptake system. The identification of MetJ binding sites (in gram-negative bacteria) or S-boxes (in gram-positive bacteria) in the promoter regions of several MUT transporter-encoding operons suggests that many MUT family members transport organic sulfur compounds. Electronic Supplementary Material Supplementary material is available for this article if you access the article at . A link in the frame on the left on that page takes you directly to the supplementary material.     

岩兰草油对淡水藻类的抑制作用

利用植物分泌的化感物质进行藻类控制已成为国内外生态环境领域研究的热点之一。首次探讨了岩兰草油的抑藻效应,建立了岩兰草油对铜绿微囊藻和斜生栅藻两种藻共培养时抑制作用的数学模型,采用GC-MS分析方法对岩兰草油中主要成分进行了鉴定。结果表明:岩兰草油对铜绿微囊藻和斜生栅藻在单独和共培养状态下均有良好的抑制作用,对单独培养的铜绿微囊藻和斜生栅藻抑制作用的EC50分别为0.20和0.30 m L/L,说明岩兰草油对蓝藻(铜绿微囊藻)的抑制效果明显好于对绿藻(斜生栅藻)。岩兰草油的主要成分为具有良好抑藻作用的倍半萜类物质,而所建立的岩兰草油对两藻共培养状态下抑制作用的数学模型可以求出在任何时间节点上铜绿微囊藻和斜生栅藻的种群密度以及要达到抑藻最佳状态的岩兰草油浓度。该研究对水华藻类的控制有较重要的理论与应用价值。     

Carrier-mediated acetate transport in Acetobacterium woodii

Intracellular and extracellular acetate concentrations of Acetobacterium woodii DSM 1030 were determined during growth or incubation of resting cell suspensions. The internal concentrations during growth decreased from initially 350 mM to 145 mM at the end of the experiment. The intracellular pH was lowered from 7.5 to 6.6 and the pH was enlarged from 0.2 to 0.6 units. Both, growing and resting cells of A. woodii showed no equilibrium between internal and external acetate concentrations during glucose consumption; the internal concentrations were always higher than expected assuming equal concentrations of the free acid inside and outside the cells. From counterflow experiments it is suggested that acetate does not only leave A. woodii cells by passive diffusion but also by carrier-mediated transport.     

Sodium-coupled solute transport in charophyte algae: A general mechanism for transport energization in plant cells?

Ion-gradient-coupled transport systems in plants are normally electrophoretic and carry inward current. Rapid inward electrical currents elicited by K⁺, by urea and by lysine in the freshwater acidophilic alga Nitella translucens Agh. are all very strongly dependent on the presence of Na⁺ or (except in the case of K⁺) Li⁺. These results indicate that Na⁺-coupled solute transport in plants, which had previously been demonstrated only in an alkalophilic species (Chara australis), did not evolve recently as an alternative to H⁺-coupled transport in high-pH environments, and might therefore be more widely distributed than has hitherto been recognised.We are very grateful to Professor E.A.C. MacRobbie and Mr J. Banfield (Botany School, University of Cambridge) for supplies of Nitella translucens. Financial support for this work was obtained from the Australian Department of Industry, Technology and Commerce and the Joint Research Council's Biotechnology Collaboration Scheme between Britain and Australia (to N.A.W. and D.S.), and from an Agricultural and Food Research Council Grant (PG 87/501 to D.S.). D.S. was a Nuffield Foundation Science Research Fellow.     

Autoradiographic studies on the role of plasmodesmata in the transport of gibberellin

Translocation of [¹⁴C]gibberellic acid into antheridial cells of Chara vulgaris L. was investigated in relation to the presence of symplasmic connections between the antheridium and the thallus. It was found that manubria, capitular cells, and antheridial filaments were about three-fold more strongly labelled in young antheridia connected to the thallus by plasmodesmata than in older antheridia in which spontaneous symplasmic isolation had occurred. Plasmolytically induced symplasmic isolation of young antheridia severely diminished the radioactivity of all the cells, down to the level characteristic for spontaneously isolated antheridia. It is concluded that plasmodesmata are the main channel of gibberellin transport into antheridia. The change in the character of symplasmic connections during the course of morphogenesis might, among other events, constitute a signal determining a shift of cell metabolism in a new direction, in response to a rapid change in gibberellin level.Abbreviations GA_(n) gibberellin (A_n) - GA₃ gibberellic acid - IAA indole-3-acetic acid This study was supported by the Polish Academy of Sciences research project CPBP 04.01.5.05.     

Effect of temperature shock and elevated incubation temperature on androgenic embryo yield of diploid potato

Using three diploid tuber-bearing Solanum clones as anther donors, experiments were conducted on the effect of high temperature shock and elevated incubation temperature during anther culture on androgenic embryo production. Five incubation treatments were tested on two clones and three treatments were repeated in a second experiment on one of the same clones and an additional one. In the first experiment, temperature treatment, genotype, date of culture initiation, and their interactions were all significant sources of variation. A treatment combining a high temperature shock (35 °C for 12 h) with elevated incubation temperature (30/20 °C) yielded 11 times as many embryos (44 per flask) as the control 20 °C (4 per flask). By conducting several replications per day of bud collection, the significant variation due to experimental dates was separated from experimental error to provide a more sensitive test of treatment effects. Temperature shock (35 °C 12h) during anther culture did not appear to influence the subsequent conversion rate of androgenic embryos.     

Effect ofcis andtrans unsaturated fatty acids on the transport properties ofSalmonella typhimurium

The transport of α-methyl-D-glucoside and two aminoacids, L-phenylalanine and L-leucine by a temperature sensitive fatty acid requiring mutant ofSalmonella typhimurium was studied under conditions of supplementation withcis or trans-unsaturated fatty acids. The results of such experiments definitely establish a relationship between the fatty acids composition of the membrane and the transport property of the cells. Cells grown in the presence of trans-unsaturated fatty acids cannot transport so efficiently as compared to the cis-unsaturated fatty acid-grown cells except linolelaidic acid, atrans-trans-unsaturated fatty acid. Protein: phospholipid ratio of the membrane also varies significantly under such conditions. The affinity of L-phenylalanine transport carrier for the substrate changes remarkably in cells grown in the presence of differentcis or trans-unsaturated fatty acids and indicate the possible role of membrane lipids in membrane assembly as well as regulation of the activity of L-phenylalanine transport system.     

Effect of abscisic acid on the transport of assimilates in barley

The effect of abscisic acid (ABA) on assimilate transport in barley was investigated in two parallel experiments. First, the effect upon [¹⁴C]sucrose transport from the flag leaf to the ear of a single ABA application made at different stages of growth of the fruits was investigated; the effect was measured 24 h after treatment. Second, the effect of a single application of ABA made at the same stages of growth as above on grain weight of the mature plant was investigated. In both types of experiments ABA was applied once to the ear of different plants as an aqueous solution (10^-3–10^-5 M), one to five weeks after anthesis. [¹⁴C] sucrose was applied by means of agar blocks. Parallel to these experiments, the endogenous content of ABA was investigated in the developing grains. When ears were treated with ABA two or four weeks after anthesis, an increase of up to 70% in the ¹⁴C-transport from the flag leaf to the ear was observed within a 24-h period after treatment (short duration experiments). At these growth stages the endogenous concentrations of ABA were low. In sharp contrast, ABA, especially in a concentration of 10^-3 M, decreased ¹⁴C-import from the flag leaf when applied three weeks after anthesis. At this stage the endogenous ABA content had reached its maximum. Long duration experiments with a single application of ABA to the car two weeks after anthesis resulted in a marked increase of weight per thousand kernels. ABA applications made earlier or later than two weeks after anthesis either reduced the grain weight or had no effect. It is concluded that ABA is involved in the regulation of assimilate transport from the leaves to the grains, possibly by influencing the unloading of sieve tubes in the ears. Promotion or inhibition of assimilate import by exogenously applied ABA may depend on the developmental stage of the grains and on the endogenous ABA level.Abbreviations ABA abscisic acid - TKW weight per thousand kernels     

Characterization of siderophore-mediated iron transport inGeotrichum candidum,a non-siderophore producer

Summary Geotrichum candidum is capable of utilizing iron from hydroxamate siderophores of different structural classes. The relative rates of iron transport for ferrichrome, ferrichrysin, ferrioxamine B, fusigen, ferrichrome A, rhodotorulic acid, coprogen B, dimerium acid and ferrirhodin were 100%, 98%, 74%, 59%, 49%, 35%, 24%, 12% and 11% respectively. Ferrichrome, ferrichrysine and ferrichrome A inhibited [⁵⁹Fe]ferrioxamine-B-mediated iron transport by 71%, 68% and 28% respectively when added at equimolar concentrations to the radioactive complex. The inhibitory mechanism of [⁵⁹Fe]ferrioxamine B uptake by ferrichrome was non-competitive (K _i 2.4 M), suggesting that the two siderophores do not share a common transport system. Uptake of [⁵⁹Fe]ferrichrome, [⁵⁹Fe]rhodotorulic acid and [⁵⁹Fe]fusigen was unaffected by competition with the other two siderophores or with ferrioxamine B. Thus,G. candidum may possess independent transport systems for siderophores of different structural classes. The uptake rates of [¹⁴C]ferrioxamine B and⁶⁷Ga-desferrioxamine B were 30% and 60% respectively, as compared to [⁵⁹Fe]ferrioxamine B. The specific ferrous chelates, dipyridyl and ferrozine at 6 mM, caused 65% and 35% inhibition of [⁵⁹Fe]ferrioxamine uptake. From these results we conclude that, although about 70% of the iron is apparently removed from the complex by reduction prior to being transported across the cellular membrane, a significant portion of the chelated ligand may enter the cell intact. The former and latter mechanisms seem not to be mutually exclusive.     

Monosaccharide transport systems in the yeast Rhodotorula glutinis

By using d-glucose, d-xylose, d-galactose and d-fructose in the strictly aerobic yeast Rhodotorula glutinis and by comparing the half-saturation constants with inhibition constants the yeast was shown to possess a single common system for d-xylose and d-galactose (K _m's and K _i's all between 0.5 and 1.1 mM) but another distinct transport system for d-fructose. The transport of d-glucose has a special position in that glucose blocks apparently allotopically all the other systems observed although it uses at least one of them for its own transport. The different character of d-glucose uptake is underlined by its relative independence of pH (its K _m is completely pH-insensitive) in contrast with all other sugars. At low concentrations, all sugars show mutual positive cooperativity in uptake, suggesting at least two transport sites plus possibly a modifier site on the carrier.     

中国盾盘菌属分类研究概况

本文对中国已记载的盾盘菌属成员名称做了分类和命名方面的评述,报道该属六个中国新记录种,须孢盘菌广西变型描述为新变型。     

Synergistic effects of an extreme weather event and habitat fragmentation on a specialised insect herbivore

Habitat fragmentation is considered to be one of the main causes of population decline and species extinction worldwide. Furthermore, habitat fragmentation can decrease the ability of populations to resist and to recover from environmental disturbances such as extreme weather events, which are expected to occur at an increasing rate as a result of climate change. In this study, we investigated how calcareous grassland fragmentation affected the impact of the climatically extreme summer of 2003 on egg deposition rates, population size variation and survival of the blue butterfly Cupido minimus, a specialist herbivore of Anthyllis vulneraria. Immediately after the 2003 summer heat wave, populations of the host plant declined in size; this was paralleled with decreases in population size of the herbivore and altered egg deposition rates. In 2006 at the end of the monitoring period, however, most A. vulneraria populations had recovered and only one population went extinct. In contrast, several butterfly populations had gone extinct between 2003 and 2006. Extinction probability was significantly related to initial population size, with small populations having a higher risk of extinction than large populations. These results support the prediction that species of higher trophic levels are more susceptible to extinction due to habitat fragmentation and severe disturbances.     

Over-expression in E. coli and purification of the human OCTN1 transport protein

The hOCTN1 amplified from skin fibroblast RNA was cloned in pET-28a(+) or in pH6EX3 plasmid. The encoded recombinant hOCTN1 resulted in a 6-His tagged fusion protein with a 34 or 21 amino acid extra N-terminal sequence in the pET-28a(+)-hOCTN1 or in the pH6EX3-hOCTN1 constructs, respectively. Both constructs were used to express the hOCTN1 in Escherichia coli Rosetta(DE3)pLysS. The best over-expression was obtained with the pH6EX3-hOCTN1 after 6 h of induction with IPTG at 28 °C. The expressed protein with an apparent molecular mass of 54 kDa, was collected in the insoluble fraction of the cell lysate. Further improvement was obtained using the E. coli RosettaGami2(DE3)pLysS strain to express the protein encoded by pH6EX3-hOCTN1. After 6 h of induction with IPTG at 28 °C, hOCTN1 accounted for 30% of the total protein in the insoluble pellet. This protein fraction was washed with Triton X-100 and deoxycholate, solubilized with a buffer containing 0.8% Sarkosyl, 3 M urea and applied to a Ni²⁺-chelating chromatography column. The homogeneously purified hOCTN1 was eluted with a buffer containing 50 mM imidazole, 0.1% Triton X-100 and 50 mM 2-mercaptoethanol. A yield of about 3 mg purified protein per liter of cell culture was obtained.     

Mutations affecting activity and transport of haemolysin in Escherichia coli

Summary Temperature-sensitive mutants that exhibit an altered haemolytic phenotype were isolated from Escherichia coli harbouring the plasmid pHly152. Complementation with recombinant plasmids carrying one of the four hly genes (C, A, B or D) allowed localization of the hly ^ts mutations. A ts mutation in hlyC leads to a proleu exchange in amino acid position 53 of HlyC. Two ts mutations in HlyA were found in positions 312 (serpro) and 315 (thrile). Both amino acid exchanges are located in the same hydrophobic domain of HlyA which extends from amino acids 299 to 327. Two different mutations were introduced by site-specific mutagenesis in this hlyA domain: one by an exchange of ala, val to asp, glu (positions 313, 314) altering the hydrophobicity of this region and another which removes most of this hydrophobic portion. Both mutants have entirely lost the haemolytic activity but the mutant haemolysins are still efficiently transported across both membranes when hlyB and hlyD are provided. Functional HlyC is not required for the transport of the mutant haemolysins. Two site-specific mutations at the N-terminal end of hlyA (one at amino acid position 2 leading to a thrpro exchange and another deleting ile and thr at positions 4 and 5) also do not affect the transport of the altered haemolysins. The thrpro exchange enhances the haemolytic activity of the corresponding mutant, whereas the ile, thr deletion exhibits little or no effect on the haemolytic activity. Removal of the last 37 amino acids from the C-terminal end of HlyA leads to a truncated haemolysin which retains its haemolytic activity but is not secreted by the HlyB and HlyD transport system.     

Occurrence and diversity of mesophilic Shewanella strains isolated from the North-West Pacific Ocean

Although bacteria of the genus Shewanella belong to one of the readily cultivable groups of "Gammaproteobacteria", little is known about the occurrence and abundance of these microorganisms in the marine ecosystem. Studies revealed that of 654 isolates obtained from marine invertebrates (ophiuroid Amphiopholis kochii, sipuncula Phascolosoma japonicum, and holothurian Apostichopus japonicus, Cucumaria japonica), seawater and sediments of the North-West Pacific Ocean (i.e. the Sea of Japan and Iturup Is, Kurile Islands), 10.7% belonged to the genus Shewanella. The proportion of viable Shewanella species varied from 4% to 20% depending on the source of isolation. From the isolation study, representative strains of different phenotypes (from seventy presumptive Shewanella strains) were selected for detailed characterization using phenotypic, chemotaxonomic, and phylogenetic testing. 16S rDNA sequence-based phylogenetic analysis confirmed the results of tentative identification and placed the majority of these strains within only a few species of the genus Shewanella with 98-99% of 16S rDNA sequences identity mainly with S. japonica and S. colwelliana, suggesting that the strains studied might belong to these species. Numerically dominant strains of S. japonica were metabolically active and produced proteinases (gelatinases, caseinases), lipases, amylases, agarases, and alginases. Shewanella strains studied demonstrated weak antimicrobial and antifungal activities that might be an indication of their passive role in the colonization on living and non-living surfaces.