Control of competence in Vibrio fischeri

Vibrio species, including the squid symbiont Vibrio fischeri, become competent to take up DNA under specific conditions. For example, V. fischeri becomes competent when grown in the presence of chitin oligosaccharides or upon overproduction of the competence regulatory factor TfoX. While little is known about the regulatory pathway(s) that control V. fischeri competence, this microbe encodes homologs of factors that control competence in the well-studied V. cholerae. To further develop V. fischeri as a genetically-tractable organism, we evaluated the roles of some of these competence homologs. Using TfoX-overproducing cells, we found that competence depends upon LitR, the homolog of V. cholerae master quorum sensing and competence regulator HapR, and on homologs of putative pili genes that in V. cholerae facilitate DNA uptake. Disruption of genes for negative regulators upstream of LitR, namely the LuxO protein and the sRNA Qrr1, resulted in increased transformation frequencies. Unlike LitR-controlled light production, however, competence did not vary with cell density under tfoX-overexpressing conditions. Analogous to V. cholerae, the requirement for LitR could be suppressed by loss of the Dns nuclease. We also found a role for the putative competence regulator CytR. Finally, we determined that transformation frequencies varied depending on the TfoX-encoding plasmid, and developed a new dual tfoX- and litR-overexpression construct that substantially increased the transformation frequency of a less genetically-tractable strain. By advancing the ease of genetic manipulation of V. fischeri, these findings will facilitate the rapid discovery of genes involved in physiologically-relevant processes, such as biofilm formation and host colonization. Importance The ability of bacteria to take up DNA (competence) and incorporate foreign DNA into their genomes (transformation) permits them to rapidly evolve and gain new traits and/or acquire antibiotic resistances. It also facilitates laboratory-based investigations into mechanisms of specific phenotypes, such as those involved in host colonization. Vibrio fischeri has long been a model for symbiotic bacteria-host interactions as well as for other aspects of its physiology such as bioluminescence and biofilm formation. Competence of V. fischeri can be readily induced upon overexpression of the competence factor TfoX. Relatively little is known about the V. fischeri competence pathway, although homologs of factors known to be important in V. cholerae competence exist. By probing the importance of putative competence factors that control transformation of V. fischeri, this work deepens our understanding of the competence process and advances our ability to genetically manipulate this important model organism.

Mitigation of Voltage Flicker at Smart Loads with Renewable (Wind) Energy in Distribution Systems

This activity handles displaying and furthermore control of astute tons for request reaction organization under improved invasion of reasonable power ages (RPGs) at desperate degree. The raised penetration of RPGs, particularly twist control at particular degree, is defined with harming impact on voltage impact. An irreversible magnet synchronous machine based volatile rate wind control transformation structure is planned with a breeze rate considering stochastic and furthermore routine effects. The recreated wind control directly into the flow structure produces stochastic and additionally consistent power fluctuations. For the tons require criticism organization, fullconnected self-commutated catches based converters are utilize to control sharp tons (SLs). These SLs are over seen for partaking in structure transports voltage strategy and in addition glints decrease. From disperate calculations, it is observed that SLs work in improving the voltage measurements of the examination feeder.

Integrated speed/synchrophasing control of turboprop engine

ABSTRACTPropeller synchrophasing control is an active method to reduce the noise and vibration of turboprop aircraft without additional weight and power. Phase control accuracy has a great influence on the noise reduction effect of synchrophasing. An integrated power/speed/synchrophasing control strategy is proposed to improve the control precision. Speed/phase control transformation logic based on a multi-blade phase plane is adopted which can take both the rapidity of speed response and phase control precision into account, but there exists switching oscillation during the mode transform process. In order to suppress the phase fluctuation due to exterior disturbance, a slave-slave control scheme is provided to take place of a master-slave scheme. Simulation results based on an integrated turboprop engine/propeller real-time non-linear model show that speed/phase integration logic can improve the response rapidity of both the speed and phase. The precision of the control system is verified to be in acceptable range.