Tetracycline production byStreptomyces aureofaciens: the time lag of production

Summary The exact time course of phosphate consumption in a tetracycline production byStreptomyces aureofaciens has been determined. The data have been compared with model simulations according to a model proposed by Votruba et al. (1984). This led to a revision of his equation for the rate of phosphate consumption and to the proposal that phosphate is consumed proportionally to the growth rate. In contradiction to the model simulations it was found that the length of the time lag of the production is independent of the initial phosphate concentration. While the model explains the time lag through inhibition of the production by phosphate, the measured data show that there must be another or an additional reason for the lag. Simultaneously with the start of the production the organism changes from an organic substrate to ammonia as nitrogen source.All experiments have been carried out in a bubble column of 651 working volume as fed batch fermentation. An autoanalyzer and a HPLC was coupled to the reactor for automatic measurement of phosphate, ammonia, sucrose and products in short intervals. Composition of the outlet gas, pH, pO₂, temperature and weight of the substrate flasks were monitored on-line.     

The Rashomon Effect: When Ethnographers Disagree

Disagreements between ethnographers often arise because of the particular circumstances of field-work or attributes of the ethnographers. A positivist search for truth versus error may be less fruitful than a constructionist examination of the research itself. This article suggests a conceptual framework for such a constructionist approach.     

Immunoelectron microscopic studies on the localization of peptidoglycan peptide subunit pentapeptides in bacterial cell walls

The peptide subunit pentapeptide H-L-Ala-D-Glu(L-Lys-D-Ala-D-Ala-OH)-NH₂ of peptidoglycan was localized in the cell walls of several Gram-positive bacteria employing the indirect immunoferritin technique. Specific antibodies to the D-alanyl-D-alanine moiety of non-crosslinked peptide subunit pentapeptide were raised in rabbits by immunization with synthetic immunogen albumin-(CH₂CO-Gly-L-Ala-L-Ala-D-Ala-D-Ala-OH)₃₉. Specificity of these antibodies for the peptide subunit pentapeptide and not for the peptide subunit tetrapeptide was corroborated in a Farr-type radio-active hapten binding assay. Specificity of labelling with ferritin was established by immunoelectron microscopic controls, and by the excellent correlation between specific labelling of cells with ferritin and the particular peptidoglycan primary structure of bacterial strains investigated. Cells of Lactobacillus gasseri, Streptococcus pyogenes and Staphylococcus aureus revealing non-crosslinked peptide subunit pentapeptides in their peptidoglycans could specifically be labelled. Lactobacillus acidophilus and Bacillus subtilis, on the contrary, missing such pentapeptides, failed in labelling.The implication of this method to possibly localize the points of attack of penicillin or cycloserine is discussed.Abbreviations used meso-A₂pm meso-diaminopimelic acid - DSM Deutsche Sammlung für Mikroorganismen, Göttingen, FRG This paper is dedicated to Professor Gerhart Drews on the occasion of his 60th birthday     

Immunocytochemistry of magnocellular neurons of supraoptic and paraventricular nuclei of normal and Brattleboro rats with vasopressin anti-idiotype antibody

Summary A vasopressin anti-idiotype antibody was generated by immunization with purified IgG of a primary vasopressin antiserum. The anti-idiotype antibody immunostained neurons in the supraoptic and paraventricular nuclei of the hypothalamus of normal and Brattleboro rats. The distribution of immunostained perikarya in these hypothalamic nuclei together with the staining of fibers in median eminence and neural lobe was similar to that observed in normal rats with anti-vasopressin and suggests strongly that vasopressinergic neurons are being stained. Absorption studies with vasopressin and a vasopressin-binding receptor protein further indicate that a receptor associated with vasopressinergic neurons is recognized by the anti-idiotype antibody.Supported by NIH grants ES03239, NS18626 and NSF grant BNS-8310914. D.T.P. is the receipient of RCDA award NS00869     

CYTOKINESIS AND PLASMODESMATA IN ULOTHRIX1

Cytokinesis essentially similar to that of vascular plants occurs in Ulothrix, an unbranched filamentous green alga. Plasmodesmata, similar to those of vascular plants, but different from those of many other algae, are also present. Cell plate formation and plasmodesmata also occur in Stigeoclonium, a branched green alga.     

Feinstrukturen der Mikrokörper (Microbodies) des proximalen Nierentubulus

Zusammenfassung Die Feinstrukturen der Mikrokörper des Nierenepithels werden beschrieben und mit denjenigen der Leber-Mikrokörper verglichen. Als besondere Charakteristika der Nieren-Mikrokörper sind eine (nicht kristalline) nucleoide Verdichtung und eigentümliche stabförmige Ausstülpungen (Stäbe) anzusehen. Die Stäbe stellen unterschiedlich lange Zylinder mit einem Durchmesser von 100 nm dar. Im Inneren findet sich eine unmittelbar der Membran anliegende, ring- oder spiralförmig angeordnete, granuläre Struktur (Granula-Durchmesser 50 Å), die in Stablängsschnitten eine Querstreifung vortäuscht. Es wird eine in Phasen ablaufende Bildung der Mikrokörper-Stäbe angenommen: ein in der Matrix entstandener Granula-Zylinder hebt sich aus dem Mikrokörper heraus, wobei die Mikrokörper-Membran entsprechend vorgebuchtet wird, und wächst schließlich zu einem eigenständigen, allseits membranumzogenen Stab aus. Die Möglichkeit, daß die Stäbe von Mikrokörpern abgestoßen werden, wird diskutiert. — Die Segregation von Mikrokörpern in Vakuolen wird nicht als aktive Beteiligung an lytischen Prozessen, sondern als autophagischer Vorgang gedeutet.

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Fine structure of microbodies in proximal tubular epithelium of the kidney

Summary Ultrastructural observations on microbodies in normal proximal tubule cells of the rat kidney are described and compared with microbodies of hepatic parenchymal cells. After fixation in osmium tetroxide with phosphate buffer the special features of the renal microbodies are the non-crystalline nucleoid and protrusions (rods) extending from the main body. These rods are cylindrical in shape having a diameter about 100 nm and are of varying lengths. Inside the limiting membrane are ring- or spiral-like ordered profiles consisting of granules (about 50 Å in diameter) which often appeared as a row of parallel linear densities arranged at approximately right angles to the long axis of the rod. It can be demonstrated that the parallel linear pattern depends on the projection of the granules in the photographic plane. — The findings suggest that the cylindrical structures of granules are formed in the peripheral matrix of microbodies; in a second phase they are lifted outside, in part enveloped with the membrane of the microbody; in this situation, the protrusions are formed. This form of creation would explain the characteristic excentrical (tangential) relation between protrusions and the main body. The observation that rods are often seen apparently isolated in the cytoplasm without visible connection with a microbody is only discussed hypothetically, because of the plane of sectioning. — Microbodies and rods can be identified in cytosegresomes. These investigations were interpreted as an autophagic degradation and not as an active role of the enzymes of microbodies in digestive mechanisms.

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Herrn Prof. Dr. Helmut Ruska zum 60. Geburtstag gewidmet.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.

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Herrn Doz. Dr. W. Thoenes danke ich für wertvolle Hinweise und für die kritische Durchsicht des Manuskriptes.     

Ichnology and sedimentology of the early Permian deep-water deposits from the Lercara-Roccapalumba area (Western Sicily,Italy)

Summary Diverse and abundant trace fossils of the deep-waterNereites ichnofacies have been found in well-dated Early Permian deep-water turbidites (Lercara Formation) of western Sicily (Italy). Conodonts indicate a latest Artinskian to Cathedralian (late Early Permian) age. Microfossils (pelagic conodonts, albaillellid Radiolaria, paleopsychrospheric ostracods, foraminiferal associations dominated byBathysiphon), trace fossils (deep-bathyal to abyssalNereites ichnofacies) and sedimentologic data collectively indicate a deep-water environment for the Early Permian turbidites of the Lercara Formation. The dominance ofAgrichnium and of thePaleodictyon subichnogeneraSquamodictyon andMegadictyon suggests that this icnofauna is closely related in ichnotaxonomic composition to other late Paleozoic deep-water ichnofaunas. The occurrence ofAcanthorhaphe. Dendrotichnium andHelicoraphe, to date only reported from Cretaceous or Tertiary flysch deposits, suggests that the entire ichnofauna corresponds well to previously documented Silurian-Tertiary flysch ichnofaunas. Eight new ichnospecies and a new ichnosubgenus,Megadictyon, are described.     

Structural analysis and molybdenum-dependent expression of the pAO1-encoded nicotine dehydrogenase genes of Arthrobacter nicotinovorans

The genes of nicotine dehydrogenase (NDH) were identified, cloned and sequenced from the catabolic plasmid pA01 of Arthrobacter nicotinovorans. In immediate proximity to this gene cluster is the beginning of the 6-hydroxy-L-niotine oxidase (6-HLNO) gene. NDH is composed of three subunits (A, B and C) of M_r 30011, 14924 and 87677. It belongs to a family of bacterial hydroxylases with a similar subunit structure; they have molybdopterin dinucleotide, FAD and Fe-S clusters as cofactors. Here the first complete primary structure of a bacterial hydroxylase is provided. Sequence alignments of each of the NDH subunits show similarities to the sequences of eukaryotic xanthine dehydrogenase (XDH) but not to other known molybdenum-containing bacterial enzymes. Based on alignment with XDH it is inferred that the smallest subunit (NDHB) carries an iron-sulphur cluster, that the middle-sized subunit (NDHA) binds FAD, and that the largest NDH subunit (NDHC) corresponds to the molybdopterin-binding domain of XDH. Expression of both the ndh and the 6-hlno genes required the presence of nicotine and molybdenum in the culture medium. Tungsten inhibited enzyme activity but not the synthesis of the enzyme protein. The enzyme was found in A. nicotinovorans cells in a soluble form and in a membrane-associated form. In the presence of tungsten the fraction of membrane-associated NDH increased.     

Insertional mutagenesis to isolate acetate-requiring mutants in Chlamydomonas reinhardtii

Abstract An arg 7 mutant of the green alga Chlamydomonas reinhardtii was transformed with pARG7.8, a plasmid bearing the wild-type ARG 7 gene. Out of 4100 arg⁺ transformants selected on an arginine-free medium supplemented with acetate, nine failed to grow on acetate-free medium (ac⁻ mutants). The results of the genetic and molecular analysis of several ac⁻ mutants are in agreement with the hypothesis that they originated from insertion of the incoming plasmid into the nuclear genome. These mutants should constitute valuable tools for isolating the corresponding wild-type genes after plasmid rescue into Escherichia coli .