Comparative Studies of Nematically Aligned Bacterial Domains in Biofilms*

Pseudomonas aeruginosa and Staphylococcus aureus are biofilm forming opportunistic human pathogens which aggregate by excreting and collecting materials from the environment which protectively bind cells together. Our recent work with mucoid Pseudomonas aeruginosa grown in physiological concentrations of calcium cations revealed that calcium drives the development of protective microdomains in the biofilm. In particular, we observed large scale plates of nematically aligned bacteria dubbed “shields.” In this work, we are interested in exploring the generality of these structures across several P. aeruginosa mutant strains and S. aureus, as well as characterizing the nematic order parameter of shield structures across length scales where present. We hope that a comparative study of S. aureus, if it forms shield structures, will inform our understanding of the aggregation mechanism at play. To do this, we will perform confocal fluorescence microscopy studies to produce and analyze 3D reconstructions of biofilm architecture at various calcium cation concentrations.