Microbial Swimming Term Paper PDF

Jade Duroshola Microbial Swimming December 7, 2023 Mars 3550 Microscopic Dancers: Unraveling the Science Behind Microbial Swimming Embarking on a microscopic journey, these three articles open the portal to an intriguing universe where bacteria, often underrated, showcase their motile capabilities...

Jade Duroshola Microbial Swimming December 7, 2023 Mars 3550 Microscopic Dancers: Unraveling the Science Behind Microbial Swimming Embarking on a microscopic journey, these three articles open the portal to an intriguing universe where bacteria, often underrated, showcase their motile capabilities, importance in the ecosystem, and mechanisms. Bacteria are the world’s smallest cells and represent the majority of the world’s biomass. They have successfully colonized many diverse habitats including nonNewtonian fluids and can transform into sources of pathogens and cause infectious diseases. Bacteria play a vital role in oxygen, carbon, and nitrogen cycles and their behavior is dependent upon physical constraints of their habitat. Most bacteria can move on their own in the most common form, swimming, by flagella that evolved from a secretory system that consists of helical appendages rotated by specialized motors. These motors are driven by electrochemical ion gradients across the cytoplasmic membrane which can be sodium or protons depending on the species. Understanding how the flagellum operates and its mechanism, how each bacterium propels itself, and the interactions of bacteria and the environment allow readers to grasp the importance of bacteria mobility and hydrodynamics. “Bacterial Hydrodynamics” composed by Eric Lauga analyzes the biological makeup, role, and hydrodynamics of bacterial flagellum. The main form of bacterial motility is swimming and to do so, bacteria have evolved flagella which consists of slender helical appendages rotated by specialized motors. Bacteria that can swim in fluids are divided into two categories: those with a spiral-like body undergoing time-varying deformation and those whose propulsion is driven by helical flagellar filaments. Low-Reynolds number hydrodynamics is the root of the ability of flagella to initiate propulsion. As they self-propel bacteria are subject to face external constraints set by the physical world and hydrodynamics. The fundamental aspect of bacteria hydrodynamics is the ability to rotate flagella to generate propulsive forces. Fluid dynamics was used by researchers to conclude the torque-frequency relationship for the rotary motor by binding tethered bacterial flagella to beads of various sizes in fluids of different viscosities. In the counterclockwise direction, the torque is at a higher frequency while in the counterclockwise direction, the torque decreases linearly with frequency. For a bacterium to remain torque-free, the Jade Duroshola Microbial Swimming December 7, 2023 Mars 3550 cell body must counter-rotate. Although most of swimming bacteria are powered by flagella rotating in the fluid external to the cells, there are other distinctive modes of locomotion. For example, bacteria of the spirochete family have a spiral shape and undergo whole-body undulations powered by flagella. Another mode of locomotion is swimming without flagella can be seen in Spiroplasma, a type of helical bacterium whose body lacks a cell wall. Different shapes exist for bacterium locomotion because when a bacterium turns, the direction of rotation of a bacterial motor change which induces rapid polymorphic transformation. “Assembly of Dynamics of the Bacterium Flagellum” written by Armitage and Berry conveys the flagellar structure of bacteria, motor protein dynamics, and the function of stator exchanges. The bacterial flagellar motor drives the ion-driven rotation of the helical flagellum. The bacterial filament is composed of multiple copies of flagellin, a surface filament devoted to bacterial motility. Most bacteria are extremely small and cannot sense a gradient along their length, activating them to use temporal sensing. The flagellar motor structure varies amongst species, as the core of the motor consists of protein rings in the inner and in-gram negative species in the outer membrane. The rotor is connected to the hook via the periplasmic rod L and P rings (a part of the bushing) and the assembly platform for the motor is the FliF ring. This ring interfaces with FliG and FliM rings, and export proteins. FliG is a part of the C-ring, which is the torquegenerating and switching component of the rotor. FliM and FliN serve as the interface with the chemosensory system. Another imperative component of the movement of bacteria is the stator exchange. Early studies indicated that stators create ion channels coupling ion flow to rotation and mechanical work. In 2006, the stator exchange was initially directly observed. The motB gene in E.coli was substituted with motB-gfp allowing natural expression of functional motors with GFP-labeled stator proteins. For E. coli, cells deleted for Mot proteins are tethered by flagella, which means stators can function independently, and motors can operate as new stators are added. Although the stators are a complex bound to the membrane, the rotating elements of the flagellum are comprised of many protein rings resulting from the intricate folding of various proteins connected by flexible linkers. Several experiments were conducted to decipher the mechanosensing of the stator, and the rotor protein exchange. About the dependence of the stator Jade Duroshola Microbial Swimming December 7, 2023 Mars 3550 on ion motive force, an increase in load and ion motive force enhances the stability of the stator interacting with the rotor. Researchers used fluorescence intensity as a measure of MotB-GFP molecules associated with the rotor which showed that the number increased as the external viscous load increased. An advantage mechanosensing provides bacteria is the regulation of the ratio of dual-stator systems. For example, Pseudomonas aeruginosa, has two sets of stators MotAB and MotCD. Both stators are driven by PMF but are used for different functions. MotAB is used for swimming in liquid environments, while MOtCD is used at high loads to enable swarming over surfaces. A small signaling molecule, cyclic-di-GMP (c-di-GMP) controls the switch of P. aeruginosa amongst other bacteria species. Elevated levels of c-di-GMP indicate stress and support the changes connected to biofilm formation. On a surface, P. aeruginosa can swarm over a surface or develop a biofilm depending on its surroundings. Evolution has permitted different bacterial species to adapt to their environment using the dynamic exchange of stators to flourish and multiply in quality under changing conditions. By having more than one stator, bacteria can optimize their motility mechanisms. . “Bacterial active matter” by Igor S. Aranson addresses the schematics of bacterial flagella arrangements, the mechanisms of bacterial turbulence, and the collective behavior of bacteria. Bacteria are unicellular microorganisms that perform random walks called run-and-tumble behavior which assists bacteria to swim up spatial gradients. Environmental conditions and the strain upon the bacteria dictate the time between successive tumbles. Bacterial turbulence is the flow induced by collective swimming due to the combined effects of energy injection and longrange hydrodynamic interactions. Propulsion forces developed by the rotation of flagella are balanced by the viscous drag that is exerted on the bacterial body by liquids. Based on the type of propulsion mechanism, the force dipole can be negative if they are propelled from the rear or positive for swimmers that are propelled from the front. An additional factor to consider when trying to digest the collective behavior of bacteria is confinement. The effect is heightened most when the characteristic scale of the geometrical constraint is equivalent to the scale of bacterial collective motion. Jade Duroshola Microbial Swimming December 7, 2023 Mars 3550 Concerning the environment, many motile bacteria dwell in non-Newtonian environments that are exemplified by viscoelastic media and liquid crystals. In comparison to Newtonian fluids, non-Newtonian fluids result in reduced swimming speeds causing the run-and-tumble behavior of bacteria to rely on unbundling of the flagella. However, when bacteria are present in a polymer-rich solution, the unbundling is suppressed. Bacteria’s memory plays a distinct role in their speed and their track of direction. Rheotaxis is the reorientation of an organism’s body and swims motion against the direction of flow. As rheotaxis mechanisms may vary, the most natural of rheotaxis is near the walls and within the corners of a channel where the shear stress and flow of velocity are minimal. The flexibility of bacterial flagella plays a role in rheotaxis and expulsion. It is believed by the researchers of this article, that swarming has many evolutionary strengths and raises colony survival rates. Long-range hydrodynamic interactions may affect collective behavior, motility assay, and microtubule assimilation. For example, Thiovulum majus resides at the bottom of salt marshes. In comparison to E. coli, they swim faster and do not exhibit run-and-tumble behavior. Once T. majus reaches the bottom, they instinctively selforganize into a two-dimensional hexagonal lattice resulting in their direction being perpendicular to the surface. The observed behavior is ascribed to the interaction between stress and bacterial activity. Overall, the technical complexity of bacteria, their behavior changes in various environments and conditions, and flagella arrangement vary depending on species, force dipole, and habitat. In summation, the exploration of bacterial dynamics and hydrodynamics unveils a multifaceted understanding of bacterial behavior and propulsion mechanisms. The mechanosensing capabilities of stator exchanges enable bacteria to develop their motility mechanisms, showcasing evolutionary adaptations for survival. The studies conducted by the three researchers for each article display the importance of flagellum structure, bacterium’s response to Newtonian and non-Newtonian fluids, and stator exchange to aid with expression of motion. Jade Duroshola Microbial Swimming December 7, 2023 Mars 3550 Works Cited Aranson I. S. (2022). Bacterial active matter. Reports on progress in physics. Physical Society (Great Britain), 85(7), 10.1088/1361-6633/ac723d. https://doi.org/10.1088/1361-6633/ac723d Armitage, J. P., & Berry, R. M. (2020). Assembly and Dynamics of the Bacterial Flagellum. Annual review of microbiology, 74, 181–200. https://doi.org/10.1146/annurev-micro090816-093411 Lauga, E. (2016). Bacterial hydrodynamics. Annual Review of Fluid Mechanics, 48, 105-130. Mavridou, D. A. I., Gonzalez, D., Kim, W., West, S. A., & Foster, K. R. (2018). Bacteria Use Collective Behavior to Generate Diverse Combat Strategies. Current biology : CB, 28(3), 345– 355.e4. https://doi.org/10.1016/j.cub.2017.12.030 Valentini, M., & Filloux, A. (2016). Biofilms and Cyclic di-GMP (c-di-GMP) Signaling: Lessons from Pseudomonas aeruginosa and Other Bacteria. The Journal of biological chemistry, 291(24), 12547–12555. https://doi.org/10.1074/jbc.R115.711507