Optimizing a human fecal assay that elicits bacterial swarming

Abstract A distinct property of many bacteria is swarming: swift movement across a surface through flagella propulsion. Early research indicates that bacterial swarming can be a protective host response to intestinal inflammation. Central to the further study of bacterial swarming in human health is an effective and replicable assay for swarming that can accommodate complex material, such as fecal matter. To date, nearly all swarming assays described in the literature are specific for bacteria grown in culture, most often Pseudomonas . In this paper, we describe a protocol for discerning swarming of bacteria from frozen human fecal samples. Moreover, we tested 4 variables that may influence the effectiveness of the assay: the method by which frozen samples were thawed, the concentration of agar used in the Lysogenic broth (LB) agar plate, the volume of LB agar poured in the plate, and the volume of sample inoculated. We found that while the type of thaw and volume of LB agar had little to no effect on swarming, greater concentrations of agar were negatively correlated with swarming and greater volumes of the sample were positively correlated with swarming.