Navigating bacterial motility through chemotaxis: from molecular mechanisms to physiological perspectives

A ubiquitous property of bacteria is their ability to move toward more suitable environments, which can also facilitate host-associated activities like colonization and offer the cell several benefits such as bacteria moving towards a favorable gradient or away from a harmful gradient is known as chemotaxis. Bacteria achieve this by rotating flagella in clockwise and anticlockwise directions resulting in "run" and "tumble." This ability of bacteria to sense and respond to any type of change in the environmental factors like pH, osmolarity, redox potential, and temperature is a standard signal transduction system that depends on coupling proteins, which is the bacterial chemotaxis system. There are two architectures for the coupling proteins in the chemotaxis system: CheW and CheV. Typically, a signal transduction system for chemotaxis to form a core signaling complex couples CheA activity to chemoreceptor control: two CheW coupling protein molecules span a histidine kinase CheA dimer and two chemoreceptors (also known as methyl-accepting chemotaxis protein, MCP) trimers of dimers which further transfer the signal to the flagellar motor through CheY. The current review summarizes and highlights the molecular mechanism involved in bacterial chemotaxis, its physiological benefits such as locating suitable nutrients and niches for bacterial growth, and various assay techniques used for the detection of chemotactic motility.