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1. An experimental study of the effect of motile bacteria on the fluid displacement in porous media

   https://doi.org/10.1051/e3sconf/202020508008  

   Jeong, Boyoung; Zhao, Yumeng; Kang, Dong-Hun; Dai, Sheng (January 2020, E3S Web of Conferences)

   McCartney, J.S.; Tomac, I. (Ed.)

   Multiphase flow patterns in porous media largely depend on the properties of the fluids and interfaces such as viscosity, surface tension, and contact angle. Microorganisms in soils change the fluid and interfacial properties, and thus can alter multiphase fluid flow in porous media. This study investigates the impact of motile bacterium Escherichia coli ( E. coli ) on fluid displacement patterns in a microfluidic chip. The fluid displacement is observed during the saturation and the desaturation processes of the microfluidic chip with and without E.coli suspension. Time-lapse photography results show that the presence of E.coli alters the displacement patterns during the wetting and drying process and changes the residual saturation of the chip. Although studies of the impacts of motility on interfacial properties remain elusive, these results bring the expectation to the manipulation of multiphase transport in porous media and the adaptive control of industrial and environmental flow processes using active particles. 

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2. Growth of microorganisms in an interfacially driven space bioreactor analog

   https://doi.org/10.1038/s41526-020-0101-4  

   Adam, Joe A.; Gulati, Shreyash; Hirsa, Amir H.; Bonocora, Richard P. (December 2020, npj Microgravity)

   null (Ed.)

   Abstract Fluid bioreactors in microgravity environments may utilize alternative methods of containment and mixing. The ring-sheared drop (RSD) is a containerless mixing device which functions in microgravity using surface tension for containment and mixes through interfacially-driven flow. To assess the feasibility of using interfacially driven flow devices, such as the RSD, as bioreactors, Escherichia coli growth and recombinant protein expression were analyzed in a ground-based analog of the RSD called the knife edge surface viscometer (KEV). Results demonstrated that the KEV can facilitate the growth of E. coli and that growth rate increases logarithmically with increasing knife edge rotation rate, similar to the standard growth method on Earth (orbital shaker). Furthermore, the KEV was shown to be viable for supporting recombinant protein expression in E. coli at levels comparable to those achieved using standard growth methods. 

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3. No ordinary proteins: Adsorption and molecular orientation of monoclonal antibodies

   https://doi.org/10.1126/sciadv.abg2873  

   Kanthe, Ankit; Ilott, Andrew; Krause, Mary; Zheng, Songyan; Li, Jinjiang; Bu, Wei; Bera, Mrinal K.; Lin, Binhua; Maldarelli, Charles; Tu, Raymond S. (August 2021, Science Advances)

   The interaction of monoclonal antibodies (mAbs) with air/water interfaces plays a crucial role in their overall stability in solution. We aim to understand this behavior using pendant bubble measurements to track the dynamic tension reduction and x-ray reflectivity to obtain the electron density profiles (EDPs) at the surface. Native immunoglobulin G mAb is a rigid molecule with a flat, “Y” shape, and simulated EDPs are obtained by rotating a homology construct at the surface. Comparing simulations with experimental EDPs, we obtain surface orientation probability maps showing mAbs transition from flat-on Y-shape configurations to side-on or end-on configurations with increasing concentration. The modeling also shows the presence of β sheets at the surface. Overall, the experiments and the homology modeling elucidate the orientational phase space during different stages of adsorption of mAbs at the air/water interface. These finding will help define new strategies for the manufacture and storage of antibody-based therapeutics. 

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4. Nanobubble Formation by Flow Regime Switching Using a Tesla Valve

   https://doi.org/10.1021/acsomega.4c10246  

   Joseph, George; Binny, Bincy; Venter, Andre R (April 2025, ACS Omega)

   Nanobubbles (NBs) are very small gas cavities in solution, and when their sizes reach diameters around 200 nm, they exhibit special qualities with widespread application. We introduce a novel, cost-effective method for the generation of nanobubbles by flow regime cycling through a Tesla valve, a valvular condiut without moving parts. We compare the performance of Tesla valve flow regime cycling with other previously reported methods for laboratory-scale NB generation. NBs were created from CO2 or N2 and by flow regime swiching using the Tesla valve, ultrasonication, and pressure cycling. The comparison includes bubble diameter, bubble concentration, and zeta potential under individually optimized conditions. The average bubble diameter generated by the Tesla valve from CO2 was measured at 110 nm by NTA, which is similar to sonication but small compared to the bubbles produced by the pressure cycling method (140 nm). Additionally, the average concentration of bubbles created by the Tesla valve was 3.8 E8 bubbles/mL, more than sonication at 3.0 E8 bubbles/mL but fewer than pressure cycling at 2.6 E9 bubbles/mL. The surface charge was recorded at −33 mV, just below sonication at −36 mV but larger than pressure cycling at −21 mV. The results indicate that flow cycling through a Tesla valve generates NBs in the 100−200 nm range, which compares favorably to the alternative laboratory-scale methods while promising low energy consumption and easy scalability for future industrial applications. 

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5. Co-Expression of type 1 fimbriae and flagella in Escherichia coli : consequences for adhesion at interfaces

   https://doi.org/10.1039/D4SM00499J  

   Ramesh_Kumar, Udayanidhi; Nguyen, Nam T; Dewangan, Narendra K; Mohiuddin, Sayed Golam; Orman, Mehmet A; Cirino, Patrick C; Conrad, Jacinta C (July 2024, Soft Matter)

   Escherichia coli expresses surface appendages including fimbriae, flagella, and curli, at various levels in response to environmental conditions and external stimuli. Previous studies have revealed an interplay between expression of fimbriae and flagella in several E. coli strains, but how this regulation between fimbrial and flagellar expression affects adhesion to interfaces is incompletely understood. Here, we investigate how the concurrent expression of fimbriae and flagella by engineered strains of E. coli MG1655 affects their adhesion at liquid–solid and liquid–liquid interfaces. We tune fimbrial and flagellar expression on the cell surface through plasmid-based inducible expression of the fim operon and fliC-flhDC genes. We show that increased fimbrial expression increases interfacial adhesion as well as bacteria-driven actuation of micron-sized objects. Co-expression of flagella in fimbriated bacteria, however, does not greatly affect either of these properties. Together, these results suggest that interfacial adhesion as well as motion actuated by adherent bacteria can be altered by controlling the expression of surface appendages. 

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