Research Mentor(s): Mark Anderson, Research Assistant Professor
Research Mentor School/College/Department: Microbiology and Immunology, Michigan Medicine
Presentation Date: Thursday, April 22, 2021
Session: Session 5 (3pm-3:50pm)
Breakout Room: Room 11
The Gram-negative bacterial species Serraita marcescens is an opportunistic pathogen capable of causing a variety of infections in humans, including bloodstream infections. S. marcescens produces multiple surface polysaccharides, macromolecules vital for mediating interactions between a bacterium and its environment. Three surface polysaccharides of interest are capsular polysaccharides (CPS), exopolysaccharides (EPS), and the O-antigen of lipopolysaccharide. Each of these surface polysaccharides plays a different role in mediating interactions with the infection environment. Previous work has identified two CPS genetic types highly associated with bloodstream infections. The goal of this study is to determine the level of genetic diversity within the EPS and O-antigen loci and correlate genetic types to sources of S. marcescens isolates. The EPS locus of 89 S. marcescens strains from infection and environmental sources were characterized using the NCBI Genome database and compared by multisequence alignment using MAFFT. The same process was repeated with the O-antigen locus of 90 S. marcescens strains. MAFFT alignments were used to construct a phylogenetic tree of the EPS, O-antigen, and CPS loci. The genetic clades established with the previous CPS analysis were only partially maintained in the EPS and O-antigen loci, suggesting that each surface polysaccharide locus is subjected to different selective pressures and that the three loci vary independently from each other. Strong correlations were also observed between clade structure and strain isolation source for all three loci. Understanding the level of genetic diversity within the CPS, EPS, and O-antigen loci has provided insight into the evolutionary relationships of these loci and may have implications for the interactions of S. marcescens with host cells during infection.