Glycogen Metabolism in Aureobasidium Pullulans: A Glycogen Synthetase with Unusual Activation Properties

Abstract

Cultures of filamentous fungi that secrete significant amounts of exopolysaccharides are among the most difficult of fermentation fluids, presenting difficulties in the areas of aeration, agitation, mixing, and control that may in turn impact the physiology of the microorganism in an undesirable manner. The fungus Sclerotium glucanicum, which produces a potentially useful exopolysaccharide known as scleroglucan, illustrates many such difficulties. This review discusses in detail the range of physiological studies on the producing microorganism itself, including those concerning formation of “undesirable” byproducts, principally oxalate, but also, under certain conditions, other TCA cycle acids. In addition, the bioreactor technology in use for production of this type of biopolymer is discussed in relation to the difficulties such fluid types present. The potential of pneumatically agitated reactors for such production is evaluated, and the lack of fundamental studies on such reactors and on the hydrodynamics and mixing behavior of such complex fluids is pointed out.     

Senescence in cut carnation flowers: Temporal and physiological relationships among water status, ethylene, abscisic acid and membrane permeability

Changes in water status, membrane permeability, ethylene production and levels of abscisic acid (ABA) were measured during senescence of cut carnation flowers ( Dianthus caryophyllus L. cv. White Sim) in order to clarify the temporal sequence of physiological events during this post-harvest period. Ethylene production and ABA content of the petal tissue rose essentially in parallel during natural senescence and after treatment of young flowers with exogenous ethylene, indicating that their syntheses are not widely separated in time. However, solute leakage, reflecting membrane deterioration, was apparent well before the natural rise in ethylene and ABA had begun. In addition, there were marked changes in water status of the tissue, including losses in water potential (ψ_w), and turgor (ψ_p), that preceded the rise in ABA and ethylene. As senescence progressed, ψ_w continued to decline, but ψ_p returned to normal levels. These temporal relationships were less well resolved when senescence of young flowers was induced by treatment with ethylene, presumably because the time-scale had been shortened. Thus changes in membrane permeability and an associated water stress in petal tissue appear to be earlier symptoms of flower senescence than the rises in ABA or ethylene. These observations support the contention that the climacteric-like rise in ethylene production is not the initial or primary event of senescence and that the rise in ABA titre may simply be a response to changes in water status.     

Land surface phenology as an indicator of biodiversity patterns

With the rapid decline in biodiversity worldwide it is imperative to develop procedures for assessing changes in biodiversity across space. The synoptic view provided by imaging remote sensors constitutes a suitable approach for analyzing biodiversity from local to regional scales. A procedure based on the close relationship between floristic similarity and the similarity in land surface phenology was recently developed and successfully applied to assess diversity patterns using time series imagery acquired by the Moderate Resolution Imaging Spectro-radiometer (MODIS). However, as it depends on high temporal resolution remotely sensed data (e.g., MODIS), the procedure is constrained by the coarse spatial resolution characterizing these high temporal resolution data. Using an optimized technique for image fusion, we combined high temporal resolution data acquired by the MODIS sensor system with moderate spatial resolution data acquired by the Landsat TM/ETM+ sensor systems. Our results show that the MODIS/Landsat data fusion allows the characterization of land surface phenology at higher spatial resolutions, which better corresponded with information acquired within vegetation survey plots established in temperate montane forests located in Wolong Nature Reserve, Sichuan Province, China. As such, the procedure is useful for capturing changes in biodiversity induced by disturbances operating at large spatial scales and constitutes a suitable tool for monitoring and managing biodiversity.     

Isolation and characterization of Zymomonas mobilis mutants resistant to octadecyltrimethylammonium chloride,a detergent acting on hopanoid-producing bacteria

Growth of the hopanoid-producing bacterium Zymomonas mobilis was inhibited at low concentrations of the cationic detergent octadecyltrimethylammoniumchloride (OTAC). A relationship between sensitivity of Zymomonas mobilis to OTAC, presence of hopanoids and ethanol tolerance was postulated. Mutants resistant to OTAC were isolated from strains ZM1 and ZM4. They did not present any alteration of the hopanoid content and their squalene cyclases showed the same sensitity to OTAC as the parent enzymes. Resistance to OTAC paralleled pleiotropic effects including, enhanced accessibility of the membrane-bound alkaline phosphatase, important release of proteins from cells by Tris/HCl treatment, increased resistance to antibiotics and increased sensitivity to ethanol. In addition, OTAC^R mutants were also characterized by the synthesis or the overproduction of an outer membrane protein (F53) not detected on 2D-PAGE maps of parent strains and by a normal heat shock response. The role of hopanoids, heat shock proteins, protein F53 and membrane organization in ethanol tolerance is discussed.Abbreviations OTAC octadecyltrimethylammoniumchloride - SLS sodium lauryl sarcosinate     

PHYSIOLOGICAL MODIFICATIONS RELATED TO DENSITY INCREASE IN PERIPHYTIC ASSEMBLAGES 1

Periphytic communities in running waters were examined as they developed on granite rocks, concrete balls and glass slides. At equivalent cell densities, no differences in pigment concentrations, species diversity or production levels were found among the different substrata examined. Development of the assemblage appeared to result from the elongation of short algal filaments which had initially settled on the surface. As these communities matured, a distinct canopy and understory developed. Cellular metabolisms were comparable among the communities. In the understory of the communities, even though the cellular content of chl a and b did not differ, chl c and carotenoid pigment concentrations were higher than those in the over-story. Bicarbonate assimilation of Tabellaria fenestrata (Lyng.) Külz. and Eunotia pectinalisi var. pectinalis (O. F. Müll?) Rabh. was higher than that of the more abundant Tabellaria flocculosa (Roth.)Kütz. var. flocculosa IV (sensu Koppen) at both high and low cell densities. This probably reflects a seasonal succession of colonizing species. Glucose assimilation appeared to be mainly attributable to bacterial activity, and algal cells of the upper layer were less active than those of the bottom. The small amount of glucose that was incorporated by the algal cells was probably absorbed passively since its amount was in direct proportion to cell volumes.     

Thermoanaerobium lactoethylicum spec. nov. a new anaerobic bacterium from a hot spring of Kamchatka

A new anaerobic thermophilic Gram-positive, nonsporeforming bacterium strain ZE-1 was isolated from a hot spring of Kamchatka (USSR). The cells are rod-shaped, (0.5–0.8 · 2.0–20 m), non-motile. The bacterium can grow between 42 and 75°C; the optimal temperature is 65°C. The growth is possible between pH values 5.0 and 8.5; optimal pH is 7.0. The cultures grow on the media containing peptone, yeast extract, or casein hydrolysate as nitrogen sources in the presence of glucose or some other sugars, mannitol or starch. The main fermentation products of glucose are ethanol, acetate, lactate, H₂, CO₂; byproducts are propionic, butyric and isovaleric acids. Glucose is metabolized via Embden-Meyerhoff-Parnas pathway. Molecular hydrogen does not inhibit growth. The bacterium does not reduce aceton to isopropanol, but is able to form H₂S from elemental sulfur. The bacterium contains a soluble hydrogenase. This enzyme catalyzes both evolution and uptake of H₂ and is active in the presence of methyl viologen. The DNA-base composition is 34.6 mol%; the genome size 2.08x10⁹ D. The name proposed for the isolated bacterium strain ZE-1 is Thermoanaerobium lactoethylicum spec. nov.     

Importance of some factors on the dimorphism of Candida albicans

The passage between the yeast and mycelial forms of Candida albicans B 311-10 was studied by using the minimal syntehtic medium of Shepherd et al. [19] modified without biotin and with low glucose concentrations. It was observed that biotin, aminoacids and particularly pH are not important factors in the dimorphism of C. albicans. The only factor of notable importance in the passage of yeast form to mycelial form in C. albicans was glucose concentration.     

Trace elements in human parotid saliva

Although various proteins and some electrolytes have been measured in human saliva, little systematic data about the major and minor elemental components of this body fluid have been obtained. In order to obtain such data, concentrations of C, Na, P, Cl, K, Ca, Sc, Cr, Fe, Co, Zn, Se, Br, Rb, Sb, I, and Cs in human parotid saliva were measured by instrumental nuclear methods. The data obtained confirmed the relative lack of Zn in saliva of patients with hypogeusia (decreased taste acuity) and suggested that concentrations of Na, Cl, Br, and Ca followed the order: normals > hypogeusia > hyposmia (decreased smell acuity). To compare concentrations of elements in saliva with those in blood and urine, absolute concentrations were normalized to that of Na through the use of a concept called an enrichment factor. On this basis, parotid saliva is relatively depleted in Se, Zn, and Fe and enriched for most other elements relative to blood plasma indicating that the fluid is not simply a transudate of blood plasma. Using this same technique, saliva composition was found more similar to urine than blood plasma, being relatively depleted in Se, Cs, and Co, being enriched in I, Br, and Cr and having about the same relative concentrations of P, Cl, Zn, Fe, Ca, K, and Rb. As the total body concentrations of many of the enriched elements in saliva are extremely small, their enrichment in saliva suggests special roles for these elements in the oral cavity. Because of its accessibility, ease of collection, and interaction with some body constituents, saliva represents a useful, albeit neglected, tool in the diagnosis of some physiological and pathological changes in body function and in understanding important aspects of trace metal metabolism.     

A replication study of human exposure to 60-Hz fields: effects on neurobehavioral measures.

The purpose of this study was to reproduce and extend an earlier investigation of the effects of human exposure to combined, 60-Hz electric and magnetic fields. This paper presents the neurobehavioral results. Thirty men participated in one training session and four testing sessions. Subjects were randomly assigned to two groups. The 18 subjects in Group I were exposed (9 kV/m, 20 microT) and sham exposed in two counterbalanced orders. In Group II, half of 12 subjects were exposed (9 kV/m, 20 microT) every session, and the remaining half were sham exposed every session. The study was doubly blinded. Measures of cardiac interbeat interval, event-related brain potentials, and performance were obtained before, during, and after exposures. As in the earlier study, exposure to the combined field resulted in a statistically significant slowing of heart rate, in changes in late components of event-related brain potentials, and in decreased errors on a choice reaction-time task. In addition, field effects on several other measures approached statistical significance. The physiological measures obtained during exposure indicated that effects were greatest soon after the field was switched on, and again when it was switched off. The data indicate that changes in exposure level may be more important than duration of exposure for producing effects in human beings.