Abstract:
Microorganisms have developed a unique set of strategies for overcoming the challenges posed by the need to navigate through their microscopic fluid environments. They have also developed morphologies that exploit the ambient forces in their surroundings, in order to orient themselves towards a desirable destination. In their tactics we can witness rudimentary forms of the types of sensing methods used by much larger organisms. In this chapter we shall firstly discuss what constitutes a desirable destination for different types of microorganisms, before describing the variety of navigation and transport mechanisms developed by these smallest of life forms in the pursuit of their destinations. What we shall see is that the mass movement of these tiny microorganisms can actually lead to considerable and complex changes on the macroscale. Accordingly, we will describe the mathematical models that have been developed to predict the dynamics of microorganism suspensions at the macroscopic level, and how these have been tailored to incorporate the various sources of microorganism stimuli. It will be seen that these models give us some valuable insights into how such small organisms can generate such large scale influences upon their environment at large.