Surface Changes in Mild Steel Coupons from the Action of Corrosion-Causing Bacteria

Changes which occur on the surface of mild steel coupons submerged in cultures of an Fe(III)-reducing bacterium, isolated from corroded pipe systems carrying crude oil, were studied microscopically to investigate the interaction between the corrosion-causing bacterium and the corroding mild steel coupon. Under micro-aerobic conditions and in the absence of the bacteria, a dense, crystalline, amorphous coat formed on the surface of the steel coupons. In the presence of bacteria the surface coat was extensively removed, exposing the bare metal to the environment. After about 2 weeks of exposure, the removal of the surface coating was followed by colonization of the metal surface by the bacteria. Colonization was mediated by fibrous, exopolysaccharidic material formed by the bacteria. Extension of studies to other bacteria isolated from crude oil and corroded pipes reveals that the formation of exopolysaccharide fibers and possession of adherent properties are common characteristics of bacteria from crude oil systems.     

Effect of abscisic acid on CO2 exchange in Lemna gibba

The effects of abscisic acid (ABA) on photosynthesis, dark respiration, and photorespiration were studied in Lemna gibba L. plants. The initial concentration of ABA in the nutrient solution was 10⁻⁷M and in a few experiments, 10⁻⁶M. The cultures were grown in the same solution for time periods ranging from one hour to 12 days. Net photosynthesis, measured as CO₂ uptake by infrared gas analyser technique, was inhibited after four hours of ABA treatment and reached a minimum after four to seven days depending on the time of the year. After 12 days a substantial recovery of photosynthesis was observed. Dark respiration was significantly stimulated after two to seven days of ABA treatment but then returned to the control level. The transient effects of ABA on photosynthesis and dark respiration corresponded to the previously measured time course of [¹⁴C]-ABA uptake by Lemna . Photorespiration measured as oxygen inhibition of photosynthesis was not affected by ABA.     

Volatile constituents of Cupressus dupreziana and the sesquiterpenes of Cupressus sempervirens

Analysis of wood essential oil of Cupressus dupreziana revealed 26 components: 13 monoterpenes and 13 sesquiterpenes. The main components were carv     

Megagyrolithes ardescensis N. Gen., N. SP.,Trace fossile nouvelle du Valanginien d'Ardeche (France)

A new trace fossil corresponding to a spiral burrow is described in the Upper Valanginian of the Ardèche area (France). It seems to be restricted to marine hemipelagic facies (outer shelf and upper slope).     

In vitro adhesion of tufted oral streptococci toBacterionema matruchotii

The adhesive interaction between the ectosymbionts of the corn cob configuration (CCC), a naturally occurring bacterial consortium in human dental plaque, was studied. In vitro association was produced in mixed cultures consisting ofBacterionema matruchotii and streptococci resemblingStreptococcus sanguis previously isolated from human CCC. Phase-contrast, selective immunofluorescence, and scanning electron microscopy showed that in this aggregative system, a tuftlike polar structure typical of the coccal epibiont mediated binding to the core filament. This aggregative model provides evidence that a specialized structure on the cell surface of epiphytic organisms may participate in interbacterial adherence.     

Réflexions critiques sur l'écologieet la systématique des Lingules actuelles et fossiles

New topics on ecology and systematics of recent and fossil Lingulids lead to an obvious revision of our knowledges on this zoological group. At first, the recent species need systematics and taxonomy on the bases of new described specific criteria (as, morphology of deltidial areas, muscle disposition); the results are briefly indicated. But, in fossil species, disorder and disparity of used characteristics are emphasized.The general conceiving on ecology of Lingulids are reviewed and discussed, especially on bathymetry and salinity; sediment and oxygenation conditions; taphocoenosis and lingulid «communities. On recent species, all these points are also studied, especially some ecological requirements (salinity, bathymetry, grain size), and mechanism of burrowing ability, burrow living positions in the sediments, as shell preservations after death and fossilization, to facilitate the paleobiotope interpretations. Recent animals are euryhalin, surviving at salinities from about 13 to 42‰; they could be considered as well adapted to waters with strong salinity fluctuations. They show preference to fine sand bottoms (lowest particle size about 40–60 μm). Their bathymetric distribution occurs between 0 and about 500 m (Lingula especially between 5–50 m; Glottidia 15–70 m). The isotherms 8–10°C seem to restrict their geographical and bathymetric distribution.Therefore, some post-palaeozoic lingulid bedsare studied or redescribed on the bases of the above discussed characteristics, and new interpretations on the environmental situation are given (Trias of Vosges Mountains; Oligocene from Japan; Eocene of London Basin). More caution must be used in study of fossil Lingulids that are not especially animals living in infralittoral bottoms with low salinity and deficient oxygenation, as generally accepted.     

Regulation of adenosine-5′-phosphosulfate sulfotransferase activity by H2S in Lemna minor L.

When Lemna minor L. is transferred to an atmosphere with H₂S, there is a rapid loss of extractable adenosine-5-phosphosulfate sulfotransferase activity. The activity is restored within 24 h in an atmosphere without H₂S. This restoration of activity is completely inhibited by cycloheximid but not by chloramphenicol. In vitro, S^2- up to 5 mM and cysteine, methionine, and glutathione up to 50 mM do not inhibit the enzyme. The activities of ATP sulfurylase and O-acetyl-L-serine sulfhydrylase are not affected significantly by H₂S. The physiological significance of the regulation of adenosine-5-phosphosulfate sulfotransferase is discussed.Abbreviations APS adenosine-5-phosphosulfate - PAPS adenosine-3-phosphate-5-phosphosulfate - BSA bovine serum albumin - DTT dithiothreitol - POPOP 1,4-di [2-(5-phenyloxazolyl)]-benzene - PPO 2,5-diphenyloxazol This is no. 6 in the series Regulation of Sulfate Assmilation in Plants