Kinetic study of phenol hydroxylase and catechol 1,2-dioxygenase biosynthesis by <Emphasis Type="Italic">Candida tropicalis</Emphasis> cells grown on different phenolic substrates

When Candida tropicalis was grown on phenol, catechol or resorcinol, the highest levels of specific activity of phenol hydroxylase (EC. 1.14.13.7) and catechol 1,2-dioxygenase (EC. 1.13.11.1) were attained with phenol. With the three aromatic compounds tested, the yeast cells exhibited sharp peaks of specific activity of both enzymes at particular incubation times. Phenol-induced cells containing high levels of both enzymes were capable of degrading rapidly and without delay 4-chlorophenol and 2,6-dichlorophenol, and to a lesser extend pentachlorophenol. However, the yeast could not grow on chlorophenols as major carbon and energy source.     

Characterization of a Human Serum Inhibitor of Clostridium histolyticum Proteinase(s)

Normal animal sera inhibit at least one Clostridium histolyticum proteinase. An assay procedure based on immune hemolysis was developed for the estimation of this inhibition. This inhibitory activity occurs in various levels in the sera of different animal species. The highest titers have been obtained with rat sera. The inhibitory activity from human serum was isolated and purified 16- to 27-fold by Sephadex G-200 gel filtration and diethylaminoethyl cellulose or hydroxylapatite chromatography. The properties of the human serum inhibitor of the clostridial proteinase were compared with a trypsin inhibiting factor found in the partially purified preparations. Identical behavior of the two inhibitory factors was observed when measured by heat inactivation, beta-mercaptoethanol sensitivity, pH stability, and sucrose gradient centrifugation. The inhibitory factor has an approximate sedimentation coefficient (S(20,w)) of 17. Goat anti-alpha-2-macroglobulin specifically precipitated the clostridial proteinase inhibitor from a partially purified preparation.     

Coral performance and bioerosion in Central Mexican Pacific reef communities

Hydrobiologia - Reef development occurs commonly under oligotrophic conditions that favor corals over competitors. In the Eastern Tropical Pacific (ETP), coral communities develop under highly...     

Temperature and water requirements for germination and effects of discontinuous hydration on germinated seed survival in Tillandsia recurvata L.

Tillandsia recurvata is an epiphytic bromeliad with a wide distribution in the Americas; however, little is known about the development of its post-seminal adaptations for survival in epiphytic environments. The purpose of this study was to define the temperature and water requirements for the germination of T. recurvata seeds. The absence of radicle emergence in T. recurvata seeds resulted in 2?stages of germination: swollen with broken seed coat (stage-1) and chlorophyllic embryos (stage-2). The effects of partial or discontinuous hydration on germinated seed survival were also assessed. The seeds were collected in a semi-arid shrubland of Mexico City. We explored: (1) whether water vapour can provide a sufficient water source for germination; (2) the temperature required for germination stage-1 and the optimal and critical osmotic potentials for germination in both germination stages; (3) the effect of seed incubation at different osmotic potentials that undergo subsequent dehydration on their survival in stage-2; and (4) the loss of dehydration tolerance during early post-seminal development. In addition, an image of T. recurvata seed anatomy was obtained to illustrate its structures. Germination stage-1 of T. recurvata seeds is rather similar across the tested temperature range. The seeds required to be in contact with liquid water to germinate. The interval of osmotic potential facilitating both germination stages was from 0 to ?0.6?MPa. Although germinated seeds displayed dehydration tolerance, this tolerance decreased in germination stage-2. The osmotic potential during germination affected the tolerance of the chlorophyllic embryos (stage-2) to subsequent dehydration.     

Olive flowering trends in a large Mediterranean area (Italy and Spain)

The aim of this study was to investigate the main climatic and biological trends related to olive flowering in central-southern Italy compared to those in Andalusia, Spain. Results since 1982 were compared for the two long-series monitoring areas of Cordoba and Perugia, and since 1992–1999 for the short-series areas. The relationship between climatic trends and the biological response of the olive, a widespread culture in the Mediterranean basin, were investigated. An aerobiological method involving capturing pollen released into the atmosphere was utilised as a bioindicator of flowering phenology. The study results confirm the strong relationship between flowering periods and spring temperature trends for the olive. Temperature during March, April and May was the parameter most related to flowering date in the study areas, particularly in Italy. In some cases we found a significant correlation between flowering and past autumn temperatures, probably due to their effect on floral bud dormancy induction, but this phenomenon appeared to be of minor importance in the studied areas. The phenological trend results show the continuous advance of flowering dates to the late 1990s, followed by a relatively stationary time series related to a short-term temperature fluctuation in the Mediterranean area. This latter period probably represents a mesoscale event forced by a macroscale event—the North Atlantic Oscillation. The results reveal that the trend towards increased temperatures, and the consequent flowering advance of some species, indicated some years ago is nowadays not as clear as was expected and should be confirmed over the next few years in the Mediterranean areas under investigation.     

Expression of the Stilbene Synthase (StSy) Gene from Grapevine in Transgenic White Poplar Results in High Accumulation of the Antioxidant Resveratrol Glucosides

When present, stilbene synthase leads to the production of resveratrol compounds, which are major components of the phytoalexin response against fungal pathogens of the plant and are highly bioactive substances of pharmaceutical interest. White poplar (Populus alba L.) was transformed with a construct containing a cDNA insert encoding stilbene synthase from grapevine (Vitis vinifera L.), under the control of the cauliflower mosaic virus (CaMV) 35S promoter, and a chimeric kanamycin resistance gene. Southern blot hybridization analysis demonstrated the presence and integration of exogenous DNA sequences in the poplar genome. Expression of the stilbene synthase-encoding gene in different transgenic lines was confirmed by Western blot and Northern analyses. Compared to the controls, in the transgenic plants two new compounds were detected and were identified as the trans- and cis-isomers of resveratrol-3-glucoside (piceid) by high-pressure liquid chromatography (HPLC), UV spectrophotometry, electrospray mass spectrometry (HPLC-ESI-MS) and enzymatic hydrolysis. Since poplar is a good biomass producer and piceids are accumulated in substantial amounts (up to 615.2 microg/g leaf fresh weight), the transgenic plants represent a potential alternative source for the production of these compounds with high pharmacological value. Despite the presence of piceid, in our experimental conditions no increased resistance against the pathogen Melampsora pulcherrima, which causes rust disease, was observed when in vitro bioassays were performed.     

Molecular hydrogen from water radiolysis as an energy source for bacterial growth in a basin containing irradiating waste

Although being deionized, filtered and therefore normally deeply oligotrophic, the water from a basin containing irradiating waste presented relatively high bacterial concentrations (ca 10(5) cfu ml(-1)) and biofilm development at its surface and on the walls. This water was characterized by a high concentration of molecular H2 due to water radiolysis, while its electrochemical potential was around +400 mV due the presence of dissolved O2 and active oxygen compounds. This combination of H2 availability and of an oxidant environment is completely original and not described in nature. From surface and wall biofilms, we enumerated the autotrophic populations ( approximately 10(5) bacteria ml(-1)) able to grow in presence of H2 as energy source and CO2 as carbon source, and we isolated the most abundant ones among cultivable bacteria. They efficiently grew on a mineral medium, in the presence of H2, O2 and CO2, the presence of the three gases being indispensable. Two strains were selected and identified using their rrs gene sequence as Ralstonia sp. GGLH002 and Burkholderia sp. GGLH005. In pure culture and using isotope exchange between hydrogen and deuterium, we demonstrated that these strains are able to oxidize hydrogen as energy source, using oxygen as an electron acceptor, and to use carbon dioxide as carbon source. These chemoautotroph hydrogen-oxidizing bacteria probably represent the pioneer bacterial populations in this basin and could be primary producers in the bacterial community.     

Neurotransmitter release regulated by a MALS-liprin-alpha presynaptic complex

Synapses are highly specialized intercellular junctions organized by adhesive and scaffolding molecules that align presynaptic vesicular release with postsynaptic neurotransmitter receptors. The MALS/Veli-CASK-Mint-1 complex of PDZ proteins occurs on both sides of the synapse and has the potential to link transsynaptic adhesion molecules to the cytoskeleton. In this study, we purified the MALS protein complex from brain and found liprin-alpha as a major component. Liprin proteins organize the presynaptic active zone and regulate neurotransmitter release. Fittingly, mutant mice lacking all three MALS isoforms died perinatally with difficulty breathing and impaired excitatory synaptic transmission. Excitatory postsynaptic currents were dramatically reduced in autaptic cultures from MALS triple knockout mice due to a presynaptic deficit in vesicle cycling. These findings are consistent with a model whereby the MALS-CASK-liprin-alpha complex recruits components of the synaptic release machinery to adhesive proteins of the active zone.