Relationship between surface chemistry, biofilm structure, and electron transfer in Shewanella anodes

A better understanding of how anode surface properties affect growth, development, and activity of electrogenic biofilms has great potential to improve the performance of bioelectrochemical systems such as microbial fuel cells. The aim of this paper was to determine how anodes with specific exposed functional groups (–N(CH3)3þ, –COOH, –OH, and –CH3), created using x-substituted alkanethiolates self-assembled monolayers attached to gold, affect the surface properties and func- tional performance of electrogenic Shewanella oneidensis MR-1 biofilms. A combination of spec- troscopic, microscopic, and electrochemical techniques was used to evaluate how electrode surface chemistry influences morphological, chemical, and functional properties of S. oneidensis MR-1 bio- films, in an effort to develop improved electrode materials and structures. Positively charged, highly functionalized, hydrophilic surfaces were beneficial for growth of uniform biofilms with the smallest cluster sizes and intercluster diffusion distances, and yielding the most efficient electron transfer. The authors derived these parameters based on 3D morphological features of biofilms that were directly linked to functional properties of the biofilm during growth and that, during polariza- tion, were directly connected to the efficiency of electron transfer to the anode. Our results indicate that substratum chemistry affects not only primary attachment, but subsequent biofilm development andbacterialphysiology.