Light-based patterning of bacterial cells through induction of biofilm formation processes

Microbes live in communities known as biofilm on many surfaces. Thus, understanding the spatially-resolved intercellular communication and signalling link would be important to elucidate the fundamental mechanisms that govern the division of labour within biofilm as well as the differentiated roles of different species within the community. To this end, different cell patterning approaches ranging from streak plate inoculation to more spatially-defined methods utilizing microfluidics have been shown to be useful for patterning different types of cells on the same surface. However, these approaches suffer from one major limitation: the inability to control the cellular state of the cells patterned on the surface. For example, it was not possible to control the cellular differentiation pathways activated in cells patterned on a surface by the streak plate inoculation approach. A recent article in PNAS described the approach of biofilm lithography that utilized light illumination to control biofilm formation and thus patterning of cells on a surface. Specifically, a light-sensitive promoter, pDawn, was coupled to a biofilm formation gene, Ag43 that enabled the induction of biofilm formation and deposition of cells on a surface upon activation of a specific wavelength of light. The approach is amenable to the use of photomask common in photolithography and enables the formation of patterns with high spatial resolution of 25 µm. However, the method suffers from unexplained degradation of the patterned biofilm after a few days and this limits its utility in long duration experiments seeking to understand cellular behaviour due to intercellular signalling. In addition, the maximal spatial resolution achieved is still multiple cell lengths away from that necessary to understand intercellular communications of cells in close contact in a biofilm. However, by coupling the light sensitive promoter to other genes important to biofilm formation processes in other microbial species, the approach could be extended in future work to the formation of different patterns of multiple microbial species to understand how different localization of different microbial species impact on the ecology and functioning of biofilms. Collectively, the approach of biofilm lithography represents an important advance in the biologist’s toolkit for patterning spatially-resolved patterns of cells for understanding how spatial location influences cell-cell communications within the same community of cells.