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 counter-clockwise 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.
@article{arxiv.1504.04089,
title = {Dynamic Clustering in Suspension of Motile Bacteria},
author = {Xiao Chen and Xiang Yang and Mingcheng Yang and Hepeng Zhang},
journal= {arXiv preprint arXiv:1504.04089},
year = {2015}
}