Dynamic clustering in suspension of motile bacteria

¹ Department of Physics and Astronomy and Institute of Natural Sciences, Shanghai Jiao Tong University Shanghai, China
² Beijing National Laboratory for Condensed Matter Physics and Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences - Beijing, China
³ Collaborative Innovation Center of Advanced Microstructures - Nanjing, China

^(a) hepeng_zhang@sjtu.edu.cn

Received: 11 June 2015
Accepted: 24 August 2015

Abstract

Bacteria suspension exhibits a wide range of collective phenomena, arising from interactions between individual cells. Here we show Serratia marcescens cells near an air-liquid interface spontaneously aggregate into dynamic clusters through surface-mediated hydrodynamic interactions. These long-lived clusters translate randomly and rotate in the counterclockwise direction; they continuously evolve, merge with others and split into smaller ones. Measurements indicate that long-ranged hydrodynamic interactions have strong influences on cluster properties. Bacterial clusters change material and fluid transport near the interface and hence may have environmental and biological consequences.