Production and structural analysis of the polysaccharide secreted by <Emphasis Type="Italic">Trametes (Coriolus) versicolor</Emphasis> ATCC 200801

Trametes versicolor ATCC 200801 secretes 4.1 g L⁻¹ of exopolysaccharide (EPS) when synthetic minimal medium and low-shear bioreactor cultivation technique are used. Structural and compositional analyses by thin layer chromatography, gas chromatography–mass spectrometry, electrospray ionization tandem mass spectrometry, and nuclear magnetic resonance spectroscopy yielded predominantly glucose and small amounts of galactose, mannose, arabinose, and xylose. The main EPS is composed of β-1,3/β-1,6-linked d-glucose molecules which is identical with Schizophyllan but does not possess a triple helical arrangement as secondary structure. Two molar mass fractions were detected by size exclusion chromatography yielding weight-average molecular weights of 4,100 and 2.6 kDa. Protein content varies between 2–3.6% (w/w). The exopolysaccharide is different in the nature of the glycosidic linkage, composition of monosaccharides, protein content, and weight-average molecular weight compared to the well-known polysaccharopeptide (PSP) and polysaccharopeptide Krestin (PSK).     

Effect of drought stress implemented at pre- or post-anthesis stage on some physiological parameters as screening criteria in chickpea cultivars

Drought is one of the most important factors limiting chickpea production in arid and semi-arid regions. There is little information regarding genotypic variation for drought tolerance in chickpea cultivars. Screening for drought tolerance is very important. It is essential to identify the physiological mechanisms of drought tolerance to complete conventional breeding program. Glasshouse experiment was carried out to study the genotypic variation among 11 chickpea (Cicer arietinum L.) cultivars. Plants were grown either under optimum conditions or drought stress was implemented at pre-or post-anthesis stages. The drought susceptibility index (DSI) was used as the measure of drought tolerance. Relationships between DSI and excised-leaf water loss (RWL), relative water content (RWC), membrane permeability, ascorbic acid, proline, and chlorophyll contents, lipid peroxidation, and hydrogen peroxide concentrations were determined in order to find out whether these physiological parameters could be used as the genotypic selection criteria for drought tolerance. The results of this study indicated that there was a wide variation in tolerance to drought stress among the chickpea cultivars, which could be exploited in breeding new chickpea cultivars with high drought tolerance. The results also demonstrated that drought-tolerant cultivars had a higher RWC, ascorbic acid and proline concentrations, but lower RWL and membrane permeability in comparison to drought-sensitive cultivars. The significant and a well defined relationships between DSI and RWC, RWL, ascorbic acid, proline, and membrane permeability were found. It was concluded that these parameters could be instrumental in predicting the drought tolerance of chickpea cultivars. This text was submitted by the authors in English.     

Avidin related protein 2 shows unique structural and functional features among the avidin protein family

Background  

The chicken avidin gene family consists of avidin and several avidin related genes (AVRs). Of these gene products, avidin is the best characterized and is known for its extremely high affinity for D-biotin, a property that is utilized in numerous modern life science applications. Recently, the AVR genes have been expressed as recombinant proteins, which have shown different biotin-binding properties as compared to avidin.     

Reactive Oxygen Species and Human Inflammatory Periodontal Diseases

Reactive oxygen species (ROS) have emerged as important signaling molecules in the regulation of various cellular processes. They can be generated by the mitochondrial electron transport chain in mitochondria and activation of polymorphonuclear leukocytes (PMN) during inflammatory conditions. Excessive generation of ROS may result in attack of and damage to most intracellular and extracellular components in a living organism. Moreover, ROS can directly induce and/or regulate apoptotic and necrotic cell death. Periodontal pathologies are inflammatory and degenerative diseases. Several forms of periodontal diseases are associated with activated PMN. Damage of tissues in inflammatory periodontal pathologies can be mediated by ROS resulting from the physiological activity of PMN during the phagocytosis of periodontopathic bacteria.__________Translated from Biokhimiya, Vol. 70, No. 6, 2005, pp. 751–761.Original Russian Text Copyright © 2005 by Canakci, Cicek, Canakci.     

Understanding aerobic/anaerobic metabolism in Caldibacillus debilis through a comparison with model organisms

Caldibacillus debilis GB1 is a facultative anaerobe isolated from a thermophilic aero-tolerant cellulolytic enrichment culture. There is a lack of representative proteomes of facultative anaerobic thermophilic Bacillaceae, exploring aerobic/anaerobic expression. The C. debilis GB1 genome was sequenced and annotated, and the proteome characterized under aerobic and anaerobic conditions while grown on cellobiose. The draft sequence of C. debilis GB1 contains a 3,340,752 bp chromosome and a 5,386 bp plasmid distributed over 49 contigs. Two-dimensional liquid chromatography mass spectrometry/mass spectrometry was used with Isobaric Tags for Relative and Absolute Quantification (iTRAQ) to compare protein expression profiles, focusing on energy production and conversion pathways. Under aerobic conditions, proteins in glycolysis and pyruvate fermentation pathways were down-regulated. Simultaneously, proteins within the tricarboxylic acid cycle, pyruvate dehydrogenase, the electron transport chain, and oxygen scavenging pathways showed increased amounts. Under anaerobic conditions, protein levels in fermentation pathways were consistent with the generated end-products: formate, acetate, ethanol, lactate, and CO₂. Under aerobic conditions CO₂ and acetate production was consistent with incomplete respiration. Through a direct comparison with gene expression profiles from Escherichia coli, we show that global regulation of core metabolism pathways is similar in thermophilic and mesophilic facultative anaerobes of the Phylum Proteobacteria and Firmicutes.