The bldC developmental locus of Streptomyces coelicolor encodes a member of a family of small DNA-binding proteins related to the DNA-binding domains of the MerR family.

The bldC locus, required for formation of aerial hyphae in Streptomyces coelicolor, was localized by map-based cloning to the overlap between cosmids D17 and D25 of a minimal ordered library. Subcloning and sequencing showed that bldC encodes a member of a previously unrecognized family of small (58- to 78-residue) DNA-binding proteins, related to the DNA-binding domains of the MerR family of transcriptional activators. BldC family members are found in a wide range of gram-positive and gram-negative bacteria. Constructed {Delta}bldC mutants were defective in differentiation and antibiotic production. They failed to form an aerial mycelium on minimal medium and showed severe delays in aerial mycelium formation on rich medium. In addition, they failed to produce the polyketide antibiotic actinorhodin, and bldC was shown to be required for normal and sustained transcription of the pathway-specific activator gene actII-orf4. Although {Delta}bldC mutants produced the tripyrrole antibiotic undecylprodigiosin, transcripts of the pathway-specific activator gene (redD) were reduced to almost undetectable levels after 48 h in the bldC mutant, in contrast to the bldC+ parent strain in which redD transcription continued during aerial mycelium formation and sporulation. This suggests that bldC may be required for maintenance of redD transcription during differentiation. bldC is expressed from a single promoter. S1 nuclease protection assays and immunoblotting showed that bldC is constitutively expressed and that transcription of bldC does not depend on any of the other known bld genes. The bldC18 mutation that originally defined the locus causes a Y49C substitution that results in instability of the protein

A connection between stress and development in the multicelular prokaryote Streptomyces coelicolor

Morphological changes leading to aerial mycelium formation and sporulation in the mycelial bacterium Streptomyces coelicolor rely on establishing distinct patterns of gene expression in separate regions of the colony. sH was identified previously as one of three paralogous sigma factors associated with stress responses in S. coelicolor. Here, we show that sigH and the upstream gene prsH (encoding a putative antisigma factor of sH) form an operon transcribed from two developmentally regulated promoters, sigHp1 and sigHp2. While sigHp1 activity is confined to the early phase of growth, transcription of sigHp2 is dramatically induced at the time of aerial hyphae formation. Localization of sigHp2 activity using a transcriptional fusion to the green fluorescent protein reporter gene (sigHp2–egfp) showed that sigHp2 transcription is spatially restricted to sporulating aerial hyphae in wild-type S. coelicolor. However, analysis of mutants unable to form aerial hyphae (bld mutants) showed that sigHp2 transcription and sH protein levels are dramatically upregulated in a bldD mutant, and that the sigHp2–egfp fusion was expressed ectopically in the substrate mycelium in the bldD background. Finally, a protein possessing sigHp2 promoter-binding activity was purified to homogeneity from crude mycelial extracts of S. coelicolor and shown to be BldD. The BldD binding site in the sigHp2 promoter was defined by DNase I footprinting. These data show that expression of sH is subject to temporal and spatial regulation during colony development, that this tissue-specific regulation is mediated directly by the developmental transcription factor BldD and suggest that stress and developmental programmes may be intimately connected in Streptomyces morphogenesis

Analysis of the Swift Gamma-Ray Bursts duration

Two classes of gamma-ray bursts have been identified in the BATSE catalogs characterized by durations shorter and longer than about 2 seconds. There are, however, some indications for the existence of a third type of burst. Swift satellite detectors have different spectral sensitivity than pre-Swift ones for gamma-ray bursts. Therefore it is worth to reanalyze the durations and their distribution and also the classification of GRBs. Using The First BAT Catalog the maximum likelihood estimation was used to analyzed the duration distribution of GRBs. The three log-normal fit is significantly (99.54 % probability) better than the two for the duration distribution. Monte-Carlo simulations also confirm this probability (99.2 %).Comment: NANJING GAMMA-RAY BURST CONFERENCE 200

Methodological approaches in the acquisition of morphological word forms

У првом делу рада се најпре полази од теоријских основа за усвајање језика и даје се преглед релевантних стручних, теоријских и методичких проучавања усвајања језика, језичких појмова и правила. Полазна теоријска основа за разматрање теме јесу научне и стручне студије које се баве лингвистиком, психолингвистиком, развојном психологијом, социолингвистиком еминентних страних и домаћих аутора. Сагледавају се унутрашњи и спољашњи фактори значајни за развој говора деце, утицај породичне средине на развој говора деце и утицај социокултурног окружења на граматички развој деце предшколског узраста и даје се преглед теорија о усвајању језика. Посебно се разматра усвајање појмова и правила у контексту теорија учења и наставе, затим се сагледавају мисаони процеси при усвајању појмова у настави морфологије, као и интуитивно усвајање појмова и правила из морфологије на млађем узрасту. У другом делу рада даје се преглед релевантне лингвистичке и методичке литературе предвиђене за усвајање морфолошког система код деце у предшколском периоду и граматичких категорија у млађим разредима основне школе. Након прегледа обраде појединих морфолошких појмова, односно граматичких категорија у граматикама намењеним средњошколском узрасту, сагледана је и њихова интерпретација у граматикама за основну школу. Тако су на овај начин истакнута најмање два нивоа учења граматичких категорија које ученици треба да савладају након првог четворогодишњег циклуса. Дат је и преглед појединих специфичних проблема при усвајању морфолошког система код деце у предшколском периоду и, посебно, у настави морфологије који је запажен и истакнут у досадашњим лингвистичким и методичким студијама..

Comparison of Different Maize Hybrids Cultivated and Fermented With or Without Sorghum

In Hungary our key forage crop is silage maize, however, the joint growing of maize and sorghum is increasingly important in arid regions. The reason is, that sorghum varieties tolerate well the various ecological stresses (drought). The joint growing of maize and sorghum varieties has several advantages and disadvantageous in respect of yields, safety of production, fermentability of the crop and nutrient content of the silage. The basis of realising the complementary qualities of the two crops and of the successful joint growing and preservation is the suitable pairing of hybrid varieties

Activity of 50 Long-Period Comets Beyond 5.2 AU

Remote investigations of the ancient solar system matter has been traditionally carried out through the observations of long-period (LP) comets that are less affected by solar irradiation than the short-period counterparts orbiting much closer to the Sun. Here we summarize the results of our decade-long survey of the distant activity of LP comets. We found that the most important separation in the dataset is based on the dynamical nature of the objects. Dynamically new comets are characterized by a higher level of activity on average: the most active new comets in our sample can be characterized by afrho values >3--4 higher than that of our most active returning comets. New comets develop more symmetric comae, suggesting a generally isotropic outflow. Contrary to this, the coma of recurrent comets can be less symmetrical, ocassionally exhibiting negative slope parameters, suggesting sudden variations in matter production. The morphological appearance of the observed comets is rather diverse. A surprisingly large fraction of the comets have long, teniouos tails, but the presence of impressive tails does not show a clear correlation with the brightness of the comets.Comment: 21 pages, 4 figures, accepted for publication in A