ABSTRACT
Studies of momentum, heat, and mass transports, originally developed as independent branches of classical physics, have grown into a unified field of fundamental engineering sciences with applications ranging from biotechnology, nanotechnology to environmental fluid mechanics. Within research fields of mass transport in aqueous environment, we might distinguish diffusive substances such as salt and sugar from mobile microorganisms with self-driving ability such as bacteria and algae playing a vital role in the nature. The mobility is an essential physiological activity of microorganisms seeking out new environment to colonize for continued growth and reproduction. Complex sensing and signaling mechanisms that allow microorganisms to move in response to external or internal cues have been described under the specific terms of “taxis” or “kinesis.” The directional responses are called taxis while the nondirectional ones are kinesis. Once a signal is received and decoded, individual movement may occur via mechanical processes such as propulsion by flagella or cilia, or gliding mobility, which relies on the frictional movement of membrane proteins against a surface to propel the microorganism forward (Van Hamme et al. 2006). Generally speaking, the movement of swimming organisms may be classified according to their responses to various stimulating factors of the environment. Principal types of taxes are reported by Eisenbach (2001).
