Visualization of Biosurfactant Film Flow in a Bacillus subtilis Swarm Colony on an Agar Plate.
Collective bacterial dynamics plays a crucial role in colony development. Although many research groups have studied the behavior of fluidic swarm colonies, the detailed mechanics of its motion remains elusive. Here, we developed a visualization method using submicron fluorescent beads for investigating the flow field in a thin layer of fluid that covers a Bacillus subtilis swarm colony growing on an agar plate. The beads were initially embedded in the agar plate and subsequently distributed spontaneously at the upper surface of the expanding colony. We conducted long-term live cell imaging of the B. subtilis colony using the fluorescent tracers, and obtained high-resolution velocity maps of microscale vortices in the swarm colony using particle image velocimetry. A distinct periodic fluctuation in the average speed and vorticity of flow in swarm colony was observed at the inner region of the colony, and correlated with the switch between bacterial swarming and growth phases. At the advancing edge of the colony, both the magnitudes of velocity and vorticity of flow in swarm colony were inversely correlated with the spreading speed of the swarm edge. The advanced imaging tool developed in this study would facilitate further understanding of the effect of micro vortices in swarm colony on the collective dynamics of bacteria.
Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC 27695, USA. kkim15@ncsu.edu.|Department of Mechanical Engineering, Kookmin University, Seoul 02707, Korea. kkim15@ncsu.edu.
Kyunghoon
K
Kim
Department of Mechanical Engineering, Kookmin University, Seoul 02707, Korea. jkkim@kookmin.ac.kr.|Department of Integrative Biomedical Science and Engineering, Kookmin University, Seoul 02707, Korea. jkkim@kookmin.ac.kr.
Jung Kyung
JK
Kim
D000362:Agar; D001412:Bacillus subtilis / Q000254:growth & development*; D003470:Culture Media
D003470:Culture Media; D000362:Agar
Bacillus subtilis; bacterial swarming; flow; fluorescent microbeads; particle image velocimetry; swarm colony