Regulation and Characterization of Mutants of in .

Symbiosis between and requires tight control of redox balance in order to maintain respiration under the microaerobic conditions required for nitrogenase while still producing the eight electrons and sixteen molecules of ATP needed for nitrogen fixation. FixABCX, a cluster of electron transfer flavoproteins essential for nitrogen fixation, is encoded on the Sym plasmid (pRL10), immediately upstream of , which encodes the general transcriptional regulator of nitrogen fixation. There is a symbiotically regulated NifA-dependent promoter upstream of (P), as well as an additional basal constitutive promoter driving background expression of (P).

Multiple sensors provide spatiotemporal oxygen regulation of gene expression in a Rhizobium-legume symbiosis.

Regulation by oxygen (O2) in rhizobia is essential for their symbioses with plants and involves multiple O2 sensing proteins. Three sensors exist in the pea microsymbiont Rhizobium leguminosarum Rlv3841: hFixL, FnrN and NifA. At low O2 concentrations (1%) hFixL signals via FxkR to induce expression of the FixK transcription factor, which activates transcription of downstream genes.

COVID-19, SARS-CoV-2, and Export Controls.

Export controls are intended to prevent the proliferation of materials that could be misused to make biological weapons. They are not intended to stifle critical research and development in the midst of a pandemic. This article explores how and why export controls might apply to severe acute respiratory syndrome coronavirus 2, the virus that causes coronavirus disease 2019.

Global control of bacterial nitrogen and carbon metabolism by a PTS-regulated switch.

The nitrogen-related phosphotransferase system (PTS) of bv. 3841 transfers phosphate from PEP via PtsP and NPr to two output regulators, ManX and PtsN. ManX controls central carbon metabolism via the tricarboxylic acid (TCA) cycle, while PtsN controls nitrogen uptake, exopolysaccharide production, and potassium homeostasis, each of which is critical for cellular adaptation and survival.

Oxygen regulatory mechanisms of nitrogen fixation in rhizobia.

Rhizobia are α- and β-proteobacteria that form a symbiotic partnership with legumes, fixing atmospheric dinitrogen to ammonia and providing it to the plant. Oxygen regulation is key in this symbiosis. Fixation is performed by an oxygen-intolerant nitrogenase enzyme but requires respiration to meet its high energy demands.

High speed two-dimensional optical beam position detector.

Disclosed is the design of a high speed two-dimensional optical beam position detector which outputs the X and Y displacement and total intensity linearly. The experimental detector measures the displacement from DC to 123 MHz and the intensity of an optical spot in a similar way as a conventional quadrant photodiode detector. The design uses four discrete photodiodes and simple dedicated optics for the position decomposition which enables higher spatial accuracy and faster electronic processing than conventional detectors.