 Hello, my name is Mikayla Tarabas and I'm a graduate student in the Enginant Lab at Cornell University. Welcome to the video abstract for our recent paper on Biotechnology and Bioengineering entitled Regulated Expression of Polysaccharide Utilization and Capsular Biosynthesis Loci in Biofilm and Planktonic Bacteroides Theta Iota Omicron during Growth and Chemostats. I'd like to tell you a little bit about the organism, which we call B Theta for short, and the findings of our study. The overall goal of this study was to use transcriptional information to better understand the physiology of bacteria that may be attached to surfaces in the human gut. B Theta is a common bacterium in the human gut where it ferments complex plant material into short chain fatty acids that are easily absorbed by its host. B Theta is found free living in the gut lumen and also as part of an attached biofilm-like community on gut surfaces and food particles. Attaching to surfaces in the gut may give B Theta an advantage by increasing accessibility of carbon sources and increasing its retention time in the gut. Whether a bacterium attaches to a surface can change its physiology dramatically, but it is difficult to study these attached communities in vivo. We took a closer look at B Theta attachment to surfaces in a bioreactor to better understand the differences between attached and free living populations of this organism. We grew B Theta in a continuously fed bioreactor or chemostat to simulate the human gut environment. We placed a piece of non-reactive graphite paper in the bioreactor as a surface for the cells to attach to. After inoculating B Theta into the reactor and allowing it to grow to a stable phase, we sampled from the surface and liquid separately, then measured whole transcriptome gene expression using aphymetrics gene chips. We compared the transcriptomes of the biofilm and planktonic samples and found widespread changes in gene expression. Nearly a quarter of all genes measured were differentially expressed between these conditions. This is visible in the graph on the left showing the difference in expression for each gene. Two of the most prominent changes were increased expression of polysaccharide utilization loci and host mucus degrading enzymes. This means that attached cells were preparing to degrade complex polysaccharides and host mucus even though they were fed with simple sugars in this study. This indicates that host mucus or complex polysaccharides may be the typical carbon sources for B Theta in attached communities. Because there were so many differences between the two populations, we put our samples in context by comparing their transcriptomes with samples from other studies performed using a wide range of growth conditions. Hierarchical clustering showed that the planktonic cells clustered with other flask-grown cultures in exponential phase as we would expect. The biofilm cells clustered with samples grown in germ-free mice. In conclusion, we found that attached populations of B Theta are primed for complex polysaccharide degradation. Higher similarity of the biofilms to mouse-grown samples also indicates that biofilms grown in chemostats may be better models of B Theta's activity in vivo than cultures grown in typical flasks. I hope that you have enjoyed this video abstract and thanks for watching.