The Acid Response in Helicobacter pylori via the Two Component System ArsRS

Helicobacter pylori is a gram-negative bacterium that colonizes the mucosal layer of the human stomach. Today, nearly half of the world population is infected with H. pylori. This infection leads to chronic inflammation, and potentially peptic ulcer disease, or gastric cancer. Developing therapeutics based on the colonization mechanism of this bacterium holds great promise as a therapeutic paradigm to promote human gastric health. To adapt to the hostile acidic environment in human stomach, H. pylori utilizes a Two-Component Signal Transduction system (TCS), ArsRS, to mediate the expression of acid response genes, such as the adhesin gene sabA and the urease component gene ureA. Here, with Electrophoretic Mobility Shift Assays (EMSA), we further demonstrated the importance of ArsR in adaptation and adherence by showing its binding activities in the promoter regions of other adhesin genes such as labA, hopZ, and sabB. Our lab has previously shown that the substitution with a phosphomimetic amino acid, such as glutamic acid (ArsR D52E) and asparagine (ArsR D52N), in the highly conserved 52nd position in ArsR preserves its acid response function, despite its inability to serve as a phosphoacceptor. Here, through site-directed mutagenesis and real-time qPCR, we discovered that the alanine substitution for adjacent aspartic acids at the 47th and 59th positions of mutant D52E retained normal sabA repression under pH5, but showed an increase in ureA induction under pH5. This study also demonstrates that ArsRS TCS failed to regulate sabA and ureA in response to pH 5 exposure when the phophoacepting histidine (H214) in ArsS was substituted with alanine (ArsS H214A), which disabled its enzymatic function. Furthermore, a kinetics experiment under constant acidity revealed that in ArsR D52E mutant, the repression of sabA occurred immediately upon exposure to acidity (time 0 min), peaked at time 150 min, and disappeared at time 210 min. The induction of ureA started at time 60 min, maximized at time 120 min, and stopped at 210 min. Together, our results demonstrate the complex nature of this TCS system. We speculate that this complex acclimation to the acid regimen of the stomach helps facilitate the decades long infection of arguably the most extreme environment associated with the human condition

Modeling and Minimizing Spontaneous Raman Scattering for QKD Secured DWDM Networks

Quantum key distribution (QKD) provides\ua0information-theoretic security based on quantum mechanics. Integrating QKD with classical data traffic by using wavelength division multiplexing (WDM) techniques in a single fibre is a cost-efficient way to improve security in legacy infrastructure. In such a system, the main noise source to the quantum channel is spontaneous Raman scattering (SRS) caused by the classical channels. In this letter we introduce a channel allocation strategy for both quantum and classical signals to minimize the SRS noise. A use case that quantum and classical channels co-exist in a dense WDM system is investigated. The results show >26% increase of achievable transmission distance for the QKD system when implementing the introduced channel allocation strategy. Moreover, a network updating plan is proposed, which provides a guideline to light the new wavelengths for classical communications while minimizing the SRS noise to quantum channels

Scalable Federated Learning over Passive Optical Networks

Two-step aggregation is introduced to facilitate scalable federated learning (SFL) over passive optical networks (PONs). Results reveal that the SFL keeps the required PON upstream bandwidth constant regardless of the number of involved clients, while bringing ~10% learning accuracy improvement.Comment: 3 pages, 5 figure

A portable device for studying the effects of fluid flow on degradation properties of biomaterials inside cell incubators.

A portable device was designed and constructed for studying the properties of biomaterials in physiologically relevant fluids under controllable flow conditions that closely simulate fluid flow inside the body. The device can fit entirely inside a cell incubator; and, thus, it can be used directly under standard cell culture conditions. An impedance-driven pump was built in the sterile flow loop to control the flow rates of fluids, which made the device small and portable for easy deployment in the incubator. To demonstrate the device functions, magnesium (Mg) as a representative biodegradable material was tested in the flow device for immersion degradation under flow versus static conditions, while the flow module was placed inside a standard cell incubator. The flow rate was controlled at 0.17 ± 0.06 ml/s for this study; and, the flow rate is adjustable through the controller module outside of incubators for simulating the flow rates in the ranges of blood flow in human artery (0.05 ∼0.43 ml/s) and vein (0.02 ∼0.08 ml/s). Degradation of Mg under flow versus static conditions was characterized by measuring the changes of sample mass and thickness, and Mg2+ ion concentrations in the immersion media. Surface chemistry and morphology of Mg after immersion under flow versus static conditions were compared. The portable impedance-driven flow device is easy to fit inside an incubator and much smaller than a peristaltic pump, providing a valuable solution for studying biomaterials and implants (e.g. vascular or ureteral stents) in body fluids under flow versus static conditions with or without cells

Efficient protection schemes for hybrid WDM/TDM passive optical networks

Hybrid WDM/TDM Passive Optical Network (PON) is a promising candidate for next-generation optical access (NGOA) solutions as it is able to offer a high splitting ratio and consequently achieves a relatively low cost and power consumption on a per-user basis compared with other NGOA architectures. On the other hand, the end users require a certain level of connection availability while the operators need to reduce the failure impact (i.e. to avoid a huge number of end users being affected by any single failure). Therefore, by evaluating the connection availability and failure impact robustness we identify the most efficient parts to provide resilience in a hybrid WDM/TDM PON from an operator and an end-user perspective. Then, we select the appropriate protection schemes to construct some novel reliable architectures and analyze their reliability performance in urban and rural scenarios. In this way, this paper provides a comprehensive insight into the most relevant protection mechanisms for hybrid WDM/TDM PONs