Novel pathway for assimilation of dimethylsulphoniopropionate widespread in marine bacteria

Dimethylsulphoniopropionate (DMSP) accounts for up to 10% of carbon fixed by marine phytoplankton in ocean surface waters, producing an estimated 11.7-103?Tmol S per year, most of which is processed by marine bacteria through the demethylation/demethiolation pathway. This pathway releases methanethiol (MeSH) instead of the climatically active gas dimethylsulphide (DMS) and enables marine microorganisms to assimilate the reduced sulphur. Despite recognition of this critical microbial transformation for over two decades, the biochemical pathway and enzymes responsible have remained unidentified. Here we show that three new enzymes related to fatty acid β-oxidation constitute the pathway that assimilates methylmercaptopropionate (MMPA), the first product of DMSP demethylation/demethiolation, and that two previously unknown coenzyme A (CoA) derivatives, 3-methylmercaptopropionyl-CoA (MMPA-CoA) and methylthioacryloyl-CoA (MTA-CoA), are formed as novel intermediates. A member of the marine roseobacters, Ruegeria pomeroyi DSS-3, requires the MMPA-CoA pathway for MMPA assimilation and MeSH production. This pathway and the ability to produce MeSH from MMPA are present in diverse bacteria, and the ubiquitous SAR11 clade bacterium Pelagibacter ubique possesses enzymes for at least the first two steps. Analysis of marine metagenomic data indicates that the pathway is widespread among bacterioplankton in the ocean surface waters, making it one of the most important known routes for acquisition of reduced carbon and sulphur by surface ocean heterotrophs.     

Checklist of the Odonata of Colorado

One hundred and one species of Odonata are recorded for Colorado, including 58 species of Anisoptera (of which 4 are new state records) and 43 Zygoptera (9 new state records). County records are indicated for each. Three major elements are recognized; predominantly eastern species occurring in the plains and mountain valleys east of the Rocky Mountains, Canadian Zone elements occurring principally above 2,440 m (8,000 ft) in the mountains, and Great Basin and western species occurring chiefly west of the mountains. The list is based primarily on the collections at Colorado State University and the University of Colorado, with additional records from the literature and from other collections.     

Sugar transporters for intercellular exchange and nutrition of pathogens

Sugar efflux transporters are essential for the maintenance of animal blood glucose levels, plant nectar production, and plant seed and pollen development. Despite broad biological importance, the identity of sugar efflux transporters has remained elusive. Using optical glucose sensors, we identified a new class of sugar transporters, named SWEETs, and show that at least six out of seventeen Arabidopsis, two out of over twenty rice and two out of seven homologues in Caenorhabditis elegans, and the single copy human protein, mediate glucose transport. Arabidopsis SWEET8 is essential for pollen viability, and the rice homologues SWEET11 and SWEET14 are specifically exploited by bacterial pathogens for virulence by means of direct binding of a bacterial effector to the SWEET promoter. Bacterial symbionts and fungal and bacterial pathogens induce the expression of different SWEET genes, indicating that the sugar efflux function of SWEET transporters is probably targeted by pathogens and symbionts for nutritional gain. The metazoan homologues may be involved in sugar efflux from intestinal, liver, epididymis and mammary cells.     

Complete subunit architecture of the proteasome regulatory particle

The proteasome is the major ATP-dependent protease in eukaryotic cells, but limited structural information restricts a mechanistic understanding of its activities. The proteasome regulatory particle, consisting of the lid and base subcomplexes, recognizes and processes polyubiquitinated substrates. Here we used electron microscopy and a new heterologous expression system for the lid to delineate the complete subunit architecture of the regulatory particle from yeast. Our studies reveal the spatial arrangement of ubiquitin receptors, deubiquitinating enzymes and the protein unfolding machinery at subnanometre resolution, outlining the substrate's path to degradation. Unexpectedly, the ATPase subunits within the base unfoldase are arranged in a spiral staircase, providing insight into potential mechanisms for substrate translocation through the central pore. Large conformational rearrangements of the lid upon holoenzyme formation suggest allosteric regulation of deubiquitination. We provide a structural basis for the ability of the proteasome to degrade a diverse set of substrates and thus regulate vital cellular processes.     

TBC-domain GAPs for Rab GTPases accelerate GTP hydrolysis by a dual-finger mechanism

Rab GTPases regulate membrane trafficking by cycling between inactive (GDP-bound) and active (GTP-bound) conformations. The duration of the active state is limited by GTPase-activating proteins (GAPs), which accelerate the slow intrinsic rate of GTP hydrolysis. Proteins containing TBC (Tre-2, Bub2 and Cdc16) domains are broadly conserved in eukaryotic organisms and function as GAPs for Rab GTPases as well as GTPases that control cytokinesis. An exposed arginine residue is a critical determinant of GAP activity in vitro and in vivo. It has been expected that the catalytic mechanism of TBC domains would parallel that of Ras and Rho family GAPs. Here we report crystallographic, mutational and functional analyses of complexes between Rab GTPases and the TBC domain of Gyp1p. In the crystal structure of a TBC-domain-Rab-GTPase-aluminium fluoride complex, which approximates the transition-state intermediate for GTP hydrolysis, the TBC domain supplies two catalytic residues in trans, an arginine finger analogous to Ras/Rho family GAPs and a glutamine finger that substitutes for the glutamine in the DxxGQ motif of the GTPase. The glutamine from the Rab GTPase does not stabilize the transition state as expected but instead interacts with the TBC domain. Strong conservation of both catalytic fingers indicates that most TBC-domain GAPs may accelerate GTP hydrolysis by a similar dual-finger mechanism.     

Germline transmission of genetically modified primordial germ cells

Primordial germ cells (PGCs) are the precursors of sperm and eggs. In most animals, segregation of the germ line from the somatic lineages is one of the earliest events in development; in avian embryos, PGCs are first identified in an extra-embryonic region, the germinal crescent, after approximately 18 h of incubation. After 50-55 h of development, PGCs migrate to the gonad and subsequently produce functional sperm and oocytes. So far, cultures of PGCs that remain restricted to the germ line have not been reported in any species. Here we show that chicken PGCs can be isolated, cultured and genetically modified while maintaining their commitment to the germ line. Furthermore, we show that chicken PGCs can be induced in vitro to differentiate into embryonic germ cells that contribute to somatic tissues. Retention of the commitment of PGCs to the germ line after extended periods in culture and after genetic modification combined with their capacity to acquire somatic competence in vitro provides a new model for developmental biology. The utility of the model is enhanced by the accessibility of the avian embryo, which facilitates access to the earliest stages of development and supplies a facile route for the reintroduction of PGCs into the embryonic vasculature. In addition, these attributes create new opportunities to manipulate the genome of chickens for agricultural and pharmaceutical applications.     

The effect of oxymetholone on tissue replacement in the rabbit's ear

Résumé L'oxymétholone est un androgène synthétique qui stimule la régénération des tissus. Son action est plus efficace que celle du phényl-propionate-nandrolone, car elle produit le replacement des tissus dès les premiers stades de la régénération chez les mâles. De plus, elle a l'avantage de pouvoir être administrée oralement.

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The authors wish to thank MissM. Tydd for technical assistance and Syntex Pharmaceuticals Limited for the supply of oxymetholone.     

Inhibitory activity of benzoyl hydrazides and hydrazine on the growth of influenza virus in chick embryo lung tissue culture

Zusammenfassung Hydrazin, wie auch verschiedene Benzoylhydrazide, hemmen das Wachstum des Influenzavirus in Kulturen embryonalen Hühnerlungengewebes. Anthranilsäurehydrazid konnte die Virusvermehrung bis 6 h nach Viruszugabe hemmen.

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This investigation was supported by a contract with the Office of Naval Research.

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From a thesis submitted in partial fulfillment for the degree of Doctor of Philosophy.

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Deceased, October 6, 1960.