Shaping the Growth Behaviour of Biofilms Initiated from Bacterial Aggregates

Bacterial biofilms are usually assumed to originate from individual cells deposited on a surface. However, many biofilm-forming bacteria tend to aggregate in the planktonic phase so that it is possible that many natural and infectious biofilms originate wholly or partially from pre-formed cell aggregates. Here, we use agent-based computer simulations to investigate the role of pre-formed aggregates in biofilm development. Focusing on the initial shape the aggregate forms on the surface, we find that the degree of spreading of an aggregate on a surface can play an important role in determining its eventual fate during biofilm development. Specifically, initially spread aggregates perform better when competition with surrounding unaggregated bacterial cells is low, while initially rounded aggregates perform better when competition with surrounding unaggregated cells is high. These contrasting outcomes are governed by a trade-off between aggregate surface area and height. Our results provide new insight into biofilm formation and development, and reveal new factors that may be at play in the social evolution of biofilm communities.GM would like to thank Diarmuid Lloyd and Bartek Waclaw for helpful discussions, and Jan Ulrich Kreft, Robert Clegg, and Kieran Alden for technical advice throughout the duration of this study. All authors wish to thank The Human Frontiers Science Program for financial support under Grant Number RGY 0081/2012. In addition GM and RA would also like to thank the EPSRC EP/J007404. Also, KK and TB were supported by the Lundbeck Foundation. KK was supported by Oticon Fonden and Knud Højgaards Fond. RJA was supported by a Royal Society University Research Fellowship.Center for Nonlinear Dynamic