Location: Bioenergy ResearchTitle: Regulated expression of polysaccharide utilization and capsular biosynthesis loci in biofilm and planktonic Bacteroides thetaiotaomicron during growth in chemostats Author
Submitted to: Biotechnology and Bioengineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2013
Publication Date: 7/30/2013
Citation: TerAvest, M.A., He, Z., Rosenbaum, M.A., Martens, E.C., Cotta, M.A., Gordon, J.I., Angenent, L.T. 2014. Regulated expression of polysaccharide utilization and capsular biosynthesis loci in biofilm and planktonic Bacteroides thetaiotaomicron during growth in chemostats. Biotechnology and Bioengineering. 111(1):165-173. Interpretive Summary: The mammalian gut, especially the colon, is inhabited by a dense and diverse population of microorganisms which significantly impact the health, nutrition, and well being of the host animal including humans and important livestock species such as cattle and swine. The predominant organisms present are anaerobic bacteria and they are involved in a variety of biodegradation activities occurring in the gut including breakdown of dietary fibers and proteins as well as host derived polymers (e.g. polysaccharides). While much is known about the activities of individual microorganisms, little is known about how they attach to the surface of the gut and how this impacts them. In the current research we studied gene expression of an important gut bacterium, Bacteroides thetaiotaomicron, living either as freely suspended or attached populations. It was discovered that attachment produced changes in the expression of genes involved in carbohydrate utilization and the synthesis cell surface carbohydrates. The results of this research were compared to those obtained with (gnotobiotic) mice colonized with known strains of gut microbes and validated this experimental approach as a way of studying such phenomena. This research will be of value to researchers studying the interaction of gut microbes and their hosts including animal physiologies and nutritionists.
Technical Abstract: Bacteroides thetaiotaomicron is a prominent member of the human distal gut microbiota that specializes in breaking down diet and host-derived polysaccharides. While polysaccharide utilization has been well studied in B. thetaiotaomicron, other aspects of its behavior are less well characterized, including the factors that allow it to maintain itself in the gut. Biofilm formation may be a mechanism for bacterial retention in the gut. Therefore, we used custom GeneChips to compare the transcriptomes of biofilm and planktonic B. thetaiotaomicron during growth in mono-colonized chemostats. We identified 1154 genes with a fold-change greater than 2, with confidence greater than or equal to 95%. Among the prominent changes observed in biofilm populations were: (i) greater expression of genes in polysaccharide utilization loci that are involved in foraging of O-glycans normally found in the gut mucosa; and (ii) regulated expression of capsular polysaccharide biosynthesis loci. Hierarchical clustering of the data with different datasets, which were obtained during growth under a range of conditions in minimal media and in intestinal tracts of gnotobiotic mice, revealed that within this group of differentially expressed genes, biofilm communities were more similar to the in vivo samples than to planktonic cells and exhibited features of substrate limitation. The current study also validates the use of chemostats as an in vitro 'gnotobiotic' model to study gene expression of attached populations of this bacterium. This is important to gut microbiota research, because bacterial attachment and the consequences of disruptions in attachment are difficult to study in vivo.