Enterobacter Sp. SM3 Exhibits Run-and-Tumble Motility

The recent discovery of the peritrichous, swarm-competent bacterium Enterobacter sp. SM3 has offered a new opportunity to elucidate the role of swarming motility in the gut microbiome. Here we present first findings of the run-and-tumble behavior of SM3 in both a control solution of motility buffer and upon bulk exposure to the chemoattractants serine and aspartate, drawing a comparison with the well-studied behavior of E. coli. It was found that SM3 runs with an average speed of approximately 30 {micro}m/s for an average duration of 0.77 s. Tumble events occur for an average duration of 0.11 s with a 69{whitebullet} average tumble angle. Both values are similar to that of E. coli. When exposed to serine, SM3 suppresses the frequency of tumble events, which in turn increases the average run duration. In addition, the average tumble angle was found to decrease in response to serine. However, when exposed to up to a millimolar concentration of aspartate, SM3 does not demonstrate a notable change in run-and-tumble parameters. These results suggest that run-and-tumble is the characteristic swimming behavior of SM3 in its planktonic state. These findings serve as a benchmark in a quest to determine the connection among swimming, swarming, and the complex dynamics of the gut microbiome. IMPORTANCEBacteria form the largest domain of living creatures on this planet. Our interactions with bacteria influence us in many ways, not the least of which being in regards to human health. A recently identified species of gut bacteria, Enterobacter sp. SM3, has been shown to reduce intestinal inflammation, suggesting that swarming could play a physiologically beneficial role. In this report, we study the motility of individual SM3 bacteria This study is an essential step towards an overarching goal to understand the influence of bacterial motility on human health.