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

The guanine nucleotide exchange factor RIC8 regulates conidial germination through Gα proteins in Neurospora crassa.

Heterotrimeric G protein signaling is essential for normal hyphal growth in the filamentous fungus Neurospora crassa. We have previously demonstrated that the non-receptor guanine nucleotide exchange factor RIC8 acts upstream of the Gα proteins GNA-1 and GNA-3 to regulate hyphal extension. Here we demonstrate that regulation of hyphal extension results at least in part, from an important role in control of asexual spore (conidia) germination. Loss of GNA-3 leads to a drastic reduction in conidial germination, which is exacerbated in the absence of GNA-1. Mutation of RIC8 leads to a reduction in germination similar to that in the Δgna-1, Δgna-3 double mutant, suggesting that RIC8 regulates conidial germination through both GNA-1 and GNA-3. Support for a more significant role for GNA-3 is indicated by the observation that expression of a GTPase-deficient, constitutively active gna-3 allele in the Δric8 mutant leads to a significant increase in conidial germination. Localization of the three Gα proteins during conidial germination was probed through analysis of cells expressing fluorescently tagged proteins. Functional TagRFP fusions of each of the three Gα subunits were constructed through insertion of TagRFP in a conserved loop region of the Gα subunits. The results demonstrated that GNA-1 localizes to the plasma membrane and vacuoles, and also to septa throughout conidial germination. GNA-2 and GNA-3 localize to both the plasma membrane and vacuoles during early germination, but are then found in intracellular vacuoles later during hyphal outgrowth

Nonlinear coupled Alfv\'{e}n and gravitational waves

In this paper we consider nonlinear interaction between gravitational and electromagnetic waves in a strongly magnetized plasma. More specifically, we investigate the propagation of gravitational waves with the direction of propagation perpendicular to a background magnetic field, and the coupling to compressional Alfv\'{e}n waves. The gravitational waves are considered in the high frequency limit and the plasma is modelled by a multifluid description. We make a self-consistent, weakly nonlinear analysis of the Einstein-Maxwell system and derive a wave equation for the coupled gravitational and electromagnetic wave modes. A WKB-approximation is then applied and as a result we obtain the nonlinear Schr\"{o}dinger equation for the slowly varying wave amplitudes. The analysis is extended to 3D wave pulses, and we discuss the applications to radiation generated from pulsar binary mergers. It turns out that the electromagnetic radiation from a binary merger should experience a focusing effect, that in principle could be detected.Comment: 20 pages, revtex4, accepted in PR

Fast Magnetosonic Waves Driven by Gravitational Waves

The propagation of a gravitational wave (GW) through a magnetized plasma is considered. In particular, we study the excitation of fast magnetosonic waves (MSW) by a gravitational wave, using the linearized general-relativistic hydromagnetic equations. We derive the dispersion relation for the plasma, treating the gravitational wave as a perturbation in a Minkowski background space-time. We show that the presence of gravitational waves will drive magnetosonic waves in the plasma and discuss the potential astrophysical implications.Comment: 12 pages, 2 figures, Astronomy and Astrophysics in pres

FEASIBILITY STUDY OF PRESSURE PULSING PIPELINE UNPLUGGING TECHNOLOGIES FOR HANFORD

The ability to unplug key waste transfer routes is generally essential for successful tank farms operations. All transfer lines run the risk of plugging but the cross site transfer line poses increased risk due to its longer length. The loss of a transfer route needed to support the waste feed delivery mission impacts the cost and schedule of the Hanford clean up mission. This report addresses the engineering feasibility for two pressure pulse technologies, which are similar in concept, for pipeline unplugging

Third-order nonlinear optical response and photoluminescence characterization of tellurite glasses with different alkali metal oxides as network modifiers

Studies of the third-order nonlinear optical properties in TeO(2)-MO-R(2)O glasses with three different alkali metal oxides R(2)O (R - Li, Na, K) as network modifiers and two network intermediates MO (M - Zn, Mg) are reported. The influence of such modifiers and intermediates on the nonlinear optical properties of these glasses was investigated using the standard Z-scan and the thermally managed Z-scan techniques under femtosecond pulse excitation at 800 nm. For different modifiers and intermediates, the nonlinear refraction indices n(2) of these glasses varied in the range 1.31-2.81 (x10(-15) cm(2)/W). It was found that n(2) increases as the ionic radius of both network modifiers and intermediates decreases. Furthermore, the measurements show that the contribution from thermo-optical effects to the nonlinear refraction index is negligible for all of the studied glass compositions. In addition, the effect of modifiers and intermediates in the formation of localized states in the vicinity of the optical bandgap was also studied through photoluminescence experiments. These experiments revealed the presence of two emission bands (red and blue) originating from these localized states that can be populated after optical excitation and subsequent relaxation