Effect of CSLM imaging rate on biofilms of P. aeruginosa and S. aureus

Biofilms are sessile communities of bacteria that can be found in an wide range of environments. Their inhabitants are phenotypically distinct from plank- tonic bacteria and are capable of forming complex, three-dimensional structures. Biofilms are studied using confocal scanning laser microscopy, or CSLM. This technique uses lasers and Novel Fluorescent Proteins (NFPs) to measure growth and structure formation of single- and multi-species biofilms in situ in three dimensions. We investigate the effects of slow and fast rates of image acquisition on mono- and co-cultures of biofilm forming bacteria: Pseudomonas aeruginosa and Staphylococcus aureus. After calculating growth rates and lag times, we find that fast scanning rates reduce the growth rate of P. aeruginosa in co-culture. Additionally, co-culture speeds up P. aeruginosa growth relative to monoculture when imaged at a slow rate, and fast scanning reverts co-culture growth to monoculture-like behavior. Additionally, a significant lag time is observed for P. aeruginosa grown in co-culture. The observed influence of confocal imaging rate on population dynamics should be considered in future studies to ensure accurate measurement of bacterial phenomena.