Collective motion of bacteria and their dynamic assembly behavior

In recent years, active matter systems have attracted considerable attentions due to their complex dynamic behaviors in physical and material science. In particular, microorganism systems have served as model systems for observing dynamic assembly and collective motility of active particles and significant progresses have been made on in-depth understanding of how high density bacteria colony behaves in the non-equilibrium state. In this mini-review, we mainly focus on the collective motion of bacteria and their dynamic assembly from four aspects: (1) the general phenomenon and biological mechanism of bacterial collective motion; (2) the common experimental techniques for studying bacterial motility; (3) some active systems on exploring bacterial collective behavior, which include both non-restricted free suspensions and those in relative confined geometric space; (4) the phenomenological and descriptive statistical methods and physical models on the underlying laws that lead to large-scale coordinate patterns in multicellular systems. This review aims to give a general picture of the collective motion in bacterial active matter systems experimentally and theoretically in order to reflect the interplays between individuals among populations in motion. It is expected that the general regulation rules related to the boundary effects in the complex systems and materials can be elucidated to some extent.