Klimacharakter und Pflanzendecke

Ohne Zusammenfassung     

Studies on prolysostaphin processing and characterization of the lysostaphin immunity factor (Lif) of Staphylococcus simulans biovar staphylolyticus

Lysostaphin is an extracellular glycylglycine endopep-tidase produced by Staphylococcus simulans biovar staphylolyticus ATCC1362 that lyses staphylococcal cells by hydrolysing the polyglycine interpeptide bridges of the peptidoglycan. Renewed analysis of the sequence of the lysostaphin gene (Iss), and the sequencing of the amino-terminus of purified prolysostaphin and of mature lysostaphin revealed that lysostaphin is organized as a preproprotein of 493 amino acids (aa), with a signal peptide consisting of 36 aa, a propeptide of 211 aa from which 195 aa are organized in 15 tandem repeats of 13 aa length, and a mature protein of 246 aa. Prolysostaphin is processed in the culture supernatant of S. simulans biovar staphylolyticus by an extracellular cysteine protease. Although prolysostaphin was staphylolytically active, the mature lysostaphin was about 4.5-fold more active. The controlled expression in Staphylococcus carnosus of Iss and Iss with deletions in the prepropeptide region indicated that the tandem repeats of the propeptide are not necessary for protein export or activation of Lss, but keep Lss in a less active state. Intracellular expressed pro- and mature lysostaphin exert staphy-lolytic activity in cell-free extracts, but do not affect growth of the corresponding clones. We characterized a lysostaphin immunity factor gene (lif) which is located in the opposite direction to Iss. The expression of lif in S. carnosus led to an increase in the serine/glycine ratio of the interpeptide bridges of peptidoglycan from 2 to 35%, suggesting that lysostaphin immunity depends on serine incorporation into the interpeptide bridge. If, in addition to lif, Iss is co-expressed the serine/glycine ratio is further increased to 58%, suggesting that Lss selects for optimal serine incorporation. Lif shows similarity to FemA and FemB     

“Self” and “Non-Self” in the Control of Phytoalexin Biosynthesis: Plant Phospholipases A2 with Alkaloid-Specific Molecular Fingerprints

The overproduction of specialized metabolites requires plants to manage the inherent burdens, including the risk of self-intoxication. We present a control mechanism that stops the expression of phytoalexin biosynthetic enzymes by blocking the antecedent signal transduction cascade. Cultured cells of Eschscholzia californica (Papaveraceae) and Catharanthus roseus (Apocynaceae) overproduce benzophenanthridine alkaloids and monoterpenoid indole alkaloids, respectively, in response to microbial elicitors. In both plants, an elicitor-responsive phospholipase A2 (PLA2) at the plasma membrane generates signal molecules that initiate the induction of biosynthetic enzymes. The final alkaloids produced in the respective plant inhibit the respective PLA, a negative feedback that prevents continuous overexpression. The selective inhibition by alkaloids from the class produced in the “self” plant could be transferred to leaves of Nicotiana benthamiana via recombinant expression of PLA2. The 3D homology model of each PLA2 displays a binding pocket that specifically accommodates alkaloids of the class produced by the same plant, but not of the other class; for example, C. roseus PLA2 only accommodates C. roseus alkaloids. The interaction energies of docked alkaloids correlate with their selective inhibition of PLA2 activity. The existence in two evolutionary distant plants of phospholipases A2 that discriminate “self-made” from “foreign” alkaloids reveals molecular fingerprints left in signal enzymes during the evolution of species-specific, cytotoxic phytoalexins.     

Über den Schmelz von Beuteltieren

Ohne ZusammenfassungFrühere Zahnstudien erschienen in dieser Zeitschrift von H. Marcus und seinen Schülern.     

Ornithologische Notizen aus dem Ebrodelta

Zusammenfassung Im Ebrodelta ist, abgesehen von einigen Seen und Sümpfen, nur noch ein schmaler Küstenstreifen landwirtschaftlich ungenutzt. Hier hat sich ein Teil ursprünglichen Vogelreichtums erhalten, und hier wurde seit einigen Jahren eine Reihe faunistischer Erhebungen durchgeführt.Diese erbrachten mehrere erste Brutnachweise für Spanien oder die spanische Mittelmeerküste:Larus ridibundus, Sterna dougallii, St. sandvicensis, Haematopus ostralegus, Limosa limosa, Asio flammeus, Acrocephalus palustris. Als Rast- und Überwinterungsgebiet ist das Delta von großer Bedeutung, z. B. fürEgretta garzetta undPhoenicopterus ruber. Enge Beziehungen zur Camargue sind vielfach erkennbar, vielleicht sogar hinsichtlich der Ausbreitung vonLarus ridibundus undHaematopus ostralegus. Regelmäßige Wintervorkommen vonMarmaronetta angustirostris sind erwähnenswert.Es wird mit einigen bisher unbekannten Brutplätzen von Laro-Limicolen bekanntgemacht, von denen eine Kolonie vonSterna albifrons mit 300–400 Paaren besonders vermerkt sei. Für weitere Arten können Bestandsangaben gemacht werden.Dieses einzige, bedeutende Brut- und Rastgebiet zwischen Camargue und Coto Doñana ist in höchster Gefahr, durch intensivere landwirtschaftliche Nutzung und touristische Erschließung vernichtet zu werden.

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Resumen Datos ornitologicos sobre el Delta del Ebro. — Sin contar con charcas y marismas, el Delta del Ebro es una franja costera aun no explotada por la agricultura. Gracias a esto una numerosa variedad de aves ha podido mantenerse aprovechando las todavia persistentes condiciones orginarias del medio ambiente. Sobre estas aves se han venido acumulando en los ultimos años un buen acopio de observaciones.Se pudo constatar como nidificantes por primera vez en España o costas mediterranes a las siguientes especies:Larus ridibundus, Sterna dougalli, St. sandvicensis, Haematopus ostralegus, Limosa limosa, Asio flammeus, Acrocephalus palustris. Como lugar de invernada o refugio durante el paso el Delta del Ebro tiene un especial interes, por ejemplo paraEgretta garzetta yPhoenicopterus ruber. Se establecen algunas relaciones con la Camarga principalmente en cuanto a la expansión deLarus ridibundus yHaematopus ostralegus. Se mencionan invernadas regulares deMarmaronetta angustirostris. Se señalan algunos nuevos lugares de cria para Laro-Limicolas, merece destacarse el hallazgo de una colonia deSterna albifrons compuesta por unos 300–400 pares. Para otras especies se dan datos numerieos estimativos.El Delta del Ebro es un lugar unico y de gran importancia, situado entre la Camarga y el Coto de Doñana, que está hoy en peligro de desaparición debido a la colonización intensiva de la agricultura y a la creciente afluencia turistica.

     

Dose-response function for Painter's SCE-model

Summary The replication model for sister chromatid exchange (SCE), when introduced in 1980 by Painter, was claimed to be consistent with the one hit property of SCE. However, the argument offered in favour of the one hit property was based on a defective dose-response function, as shown in this paper, since dose as the independent parameter of any dose-response function was not included in the considerations. This missing part of the model's dose-response function is added and, by using Bessel functions, a formula for the complete dose-response function is presented. A re-examination of the newly derived function shows that, in the model, linearity holds only under certain restricted circumstances.