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Microbiological drinking water parameters
Published in Frank R. Spellman, The Drinking Water Handbook, 2017
Many bacteria are motile, and this ability to move independently is usually attributed to a special structure, the flagella (singular: flagellum). Depending on species, a cell may have a single flagellum (see Figure 6.2) (monotrichous bacteria; trichous means “hair”), one flagellum at each end (amphitrichous bacteria; amphi means “on both sides”), a tuft of flagella at one or both ends (lophotrichous bacteria; lopho means “tuft”), or flagella that arise all over the cell surface (peritrichous bacteria; peri means “around”). A flagellum is a threadlike appendage extending outward from the plasma membrane and cell wall. Flagella are slender, rigid locomotor structures, about 20 μm across and up to 15 or 20 μm long. Flagellation patterns are very useful in identifying bacteria and can be seen by light microscopy, but only after the flagella have been stained with special techniques designed to increase their thickness. The detailed structure of flagella can be seen only in an electron microscope. Bacterial cells benefit from flagella in several ways. Flagella can increase the concentration of nutrients or decrease the concentration of toxic materials near the bacterial surfaces by causing a change in the flow rate of fluids. They can also disperse flagellated organisms to areas where colony formation can take place. The main benefit of flagella to organisms is the improved ability to flee from areas that might be harmful.
Classical Biodynamics and Biomechanics
Published in Thomas M. Nordlund, Peter M. Hoffmann, Quantitative Understanding of Biosystems, 2019
Thomas M. Nordlund, Peter M. Hoffmann
Cilia and flagella, made from bundles of microtubules and molecular motors that travel on them, provide the motile force for some bacteria as well as for eukaryotic cells. Cilia occur in single-celled eukaryotic ciliates, a group of protists characterized by the presence of hairlike cilia, similar in structure to flagella but typically shorter and present in much larger numbers. The difference between cilia and flagella is usually understood to be the sort of motion: cilia wave back and forth while flagella rotate. Cilia are also sometimes considered to be shorter than flagella. Many of these short cilia undulate in synchronism to generate forces used in swimming, crawling, attachment, and feeding. Upon stimulation by an external force, cilia may also transmit signals to the interior of the ciliate. In larger organisms such as humans, cilia are generally attached to cells that are fixed in place, and have the job of moving fluid and particles by the cells. Prokaryotic bacteria, including Escherichia coli also employ cilia and flagella for movement, though usually in smaller numbers. The multiple flagella of E. coli and other bacteria sometimes form bundles that intertwine and rotate together. As they drive the bacterium forward, they also may induce rotation. Some examples of these cilia and flagella are shown in Figure 12.13. Many others can easily be found by a Web search, including the famous example of paramecium’s large number of cilia. The terms cilia and flagella are occasionally used interchangeably (en.wikipedia.org/wiki/Flagella), so it is important to know the features of the cilium/flagellum of interest.
Numerical investigation of hybrid nanofluid with gyrotactic microorganism and multiple slip conditions through a porous rotating disk
Published in Waves in Random and Complex Media, 2022
Muhammad Naveed Khan, Shafiq Ahmad, N. Ameer Ahammad, Talal Alqahtani, Salem Algarni
In this paper a mathematical model is developed of nonlinear mixed bioconvection viscous hybrid nanofluid flow with multiple slips, chemical reactions, and joule heating impact. The following is an illustration of the paper’s primary results: The higher the values of , , and the greater the decrement impact, which lowers fluid velocity and improves temperature distribution.The temperature and mass concentration decline with the improvement of and .The fluid velocity diminishes, while the temperature increases with increasing particle solid volume fraction.Peclet number reduces the motile microorganism field, and bioconvection Lewis number boosts the motile microorganism distribution.By the enrichment of and the drag force enhances, while the opposite pattern is shown for , , ., , and decrease the motile microorganism number, while enhancing for and .