Taxonomic relations between archaebacteria including 6 novel genera examined by cross hybridization of DNAs and 16S rRNAs

DNAs from 16 species of archaebacteria including 6 novel isolates were hybridized with 16S rRNAs from 7 species representing different orders or groups of the urkingdom of archaebacteria. The yields, normalized for the number of genes per microgram of DNA, and the temperature stabilities of all hybrids were determined and related to each other. A taxonomic tree constructed from such fractional stability data reveals the same major divisions as that derived from comparative cataloging of 16S rRNA sequences. The extreme halophiles appear however as a distinct order besides the three known divisions of methanogens. The methanogens, the halophiles and Thermoplasma form one of two clearly recognizable branches of the archaebacterial urkingdom. The order represented by Sulfolobus and the related novel order Thermoproteales form the other branch. Three novel genera, Thermoproteus, Desulfurococcus and the "stiff filaments" represent three families of this order. The extremely thermophilic methanogen Methanothermus fervidus belongs to the Methanobacteriales. SN1, a methanogen from Italy, appears as another species of the genus Methanococcus. Another novel methanogen, M3, represents a genus or family of the order Methanomicrobiales.     

The effect of nisin on murein synthesis

Nisin inhibits murein synthesis with concomitant accumulation of undecaprenyl-pyrophospho-MurNAc(pentapeptide) (lipid intermediate I). This inhibition is caused by the formation of a complex between the antibiotic and lipid intermediate I. Undecaprenyl-pyrophospho-MurNAc(pentapeptide)-GlcNAc (lipid intermediate II) also forms a complex with nisin. However, when murein synthesis is inhibited by nisin, this latter complex is not formed since lipid intermediate II is no longer synthesized.Abbreviations GlcNAc N-acetylglucosamine - MurNAc N-acetylmuramyl - Pentapeptide Ala--DGlu-Lys-DAla-DAla - C₅₅ undecaprenol Dedicated to Professor Otto Kandler on occasion of his 60th birthday     

Ultrastructure of the heart of the sturgeon Acipenser stellatus (Chondrostei)

Summary The ultrastructure of atrial and ventricular myocardial cells from Acipenser stellatus is described. The cells of the atrium are more loosely connected than those of the ventricle. Cell contact is by simple intercalated discs and by desmosomes. The cells are flattened, with peripheral myofibrils and a central region of mitochondria and the nucleus. The sarcoplasmic reticulum consists of subsarcolemmal tubules, that frequently extend towards the central mitochondria. Dyads are small and positioned at any sarcomeric level. No T-tubules are present. Specific granules are restricted to the atrial cell, and are sometimes present within the SR tubules.     

Präadaption bei Flechten iranischer Halbwüsten

25 species of lichens have been collected in semidesertic to desertic areas of Iran. On the basis of spatial relations to the substrate and anatomical features of the thallus three main groups (one with a subdivision based on colour and morphology of the thallus) can be differentiated. Selective advantages and peculiarities in connection with the desert habitat are pointed out, such as inverse thallus-structure, a dense network of skeletal hyphae in the substrate in otherwise epilithic species, proliferating areolae of the thallus, immersed pycnidia with trichogynes and brownish spores in groups with usually colourless spores. Most of the species are wide-spread in arid and often also in humid regions; only one species,Verrucaria buschirensis J. Steiner, seems to be endemic. The prevalence of cyanophilic lichens in deserts may have phylogenetic reasons, as these groups appear to date back to periods without higher vegetation and a desert-like environment.

Herrn Prof. Dr. L.Geitler zum 80. Geburtstag gewidmet.     

Auxin in scapes,flower buds,flowers, and fruits of daffodil (Narcissus pseudonarcissus L.)

Summary Diffusates from flower buds, flower fruits, and scape segments, and extracts of flower stalks of Narcissus pseudonarcissus contain an auxin active in the Avena geo-curvature test. The auxin behaved like indole-3-acetic acid (IAA) in thin-layer chromatography (TLC) with neutral and basic solvents on different adsorbents. After TLC, the auxin of the extracts showed chromogenic reactions identical with those of IAA; in gas-liquid chromatography on two different columns, the purified substance, after methylation, appeared at the retention time of IAA methyl ester. The auxin content of the extracts has been estimated to be equivalent to ca. 10 g IAA kg^–1 fresh weight. Diffusates, collected at the basal end of excised flowering apices and of scape segments at different developmental stages, showed highest auxin activity when collected from old buds and young flowers, and from the basal, rapidly elongating scape regions. The diffusible auxin obtained from scape segments was very likely produced by the segments themselves. Thus, the shoot of Narcissus appears to possess two different sites of auxin production, namely, the apical region represented by the flower bud, the flower or the fruit, and the scape.Abbreviations IAA indole-3-acetic acid - IAA-OMe indole-3-acetic-acid methyl ester - TLC thin-layer chromatography - GLC gas-liquid chromatography     

Comparative analysis defines a broader FMRFamide-gated sodium channel family and determinants of neuropeptide sensitivity

FMRFamide (Phe-Met-Arg-Phe-amide, FMRFa) and similar neuropeptides are important physiological modulators in most invertebrates, but the molecular basis of FMRFa activity at its receptors is unknown. We therefore sought to identify the molecular determinants of FMRFa potency against one of its native targets, the excitatory FMRFa-gated sodium channel (FaNaC) from gastropod mollusks. Using molecular phylogenetics and electrophysiological measurement of neuropeptide activity, we identified a broad FaNaC family that includes mollusk and annelid channels gated by FMRFa, FVRIamides, and/or Wamides (or myoinhibitory peptides). A comparative analysis of this broader FaNaC family and other channels from the overarching degenerin (DEG)/epithelial sodium channel (ENaC) superfamily, incorporating mutagenesis and experimental dissection of channel function, identified a pocket of amino acid residues that determines activation of FaNaCs by neuropeptides. Although this pocket has diverged in distantly related DEG/ENaC channels that are activated by other ligands but enhanced by FMRFa, such as mammalian acid-sensing ion channels, we show that it nonetheless contains residues that determine enhancement of those channels by similar peptides. This study thus identifies amino acid residues that determine FMRFa neuropeptide activity at FaNaC receptor channels and illuminates the evolution of ligand recognition in one branch of the DEG/ENaC superfamily of ion channels.     

Rab17 Regulates Membrane Trafficking through Apical Recycling Endosomes in Polarized Epithelial Cells

A key feature of polarized epithelial cells is the ability to maintain the specific biochemical composition of the apical and basolateral plasma membrane domains while selectively allowing transport of proteins and lipids from one pole to the opposite by transcytosis. The small GTPase, rab17, a member of the rab family of regulators of intracellular transport, is specifically induced during cell polarization in the developing kidney. We here examined its intracellular distribution and function in both nonpolarized and polarized cells. By confocal immunofluorescence microscopy, rab17 colocalized with internalized transferrin in the perinuclear recycling endosome of BHK-21 cells. In polarized Eph4 cells, rab17 associated with the apical recycling endosome that has been implicated in recycling and transcytosis. The localization of rab17, therefore, strengthens the proposed homology between this compartment and the recycling endosome of nonpolarized cells. Basolateral to apical transport of two membrane-bound markers, the transferrin receptor and the FcLR 5-27 chimeric receptor, was specifically increased in Eph4 cells expressing rab17 mutants defective in either GTP binding or hydrolysis. Furthermore, the mutant proteins stimulated apical recycling of FcLR 5-27. These results support a role for rab17 in regulating traffic through the apical recycling endosome, suggesting a function in polarized sorting in epithelial cells.     

The N-acylation-phosphodiesterase pathway and cell signalling

Long-chain N-acylethanolamines (NAEs) elicit a variety of biological and pharmacological effects, Anandamide (20:4n-6 NAE) and other polyunsaturated NAEs bind to the cannabinoid receptor and may thus serve as highly specific lipid mediators of cell signalling. NAEs can be formed by phospholipase D-catalyzed hydrolysis of N-acylethanolamine phospholipids or by direct condensation of ethanolamine and fatty acid, So far, most of the latter biosynthetic activity has been shown to be the reverse reaction of the NAE amidohydrolase that catalyzes NAE degradation. Thus, increasing evidence supports the hypothesis that the N-acylation-phosphodiesterase pathway yields not only saturated-monounsaturated NAEs, but polyunsaturated ones, including anandamide, as well.