Honors College

Document Type

Honors Thesis




Melody Neely

Committee Members

Edward Bernard, Robert Gundersen, Jordan LaBouff, Sally Molloy

Graduation Year

May 2021

Publication Date

Spring 5-2021


Group B Streptococcus (GBS) can be found in the vaginal and genitourinary tract of females, as well as the genitourinary tract of males, where it behaves as a commensal organism. However, as an opportunistic pathogen, GBS has the capability to infect the immunocompromised, making it a major threat to neonates and fetuses. The pathogen can be passed from mother to baby either in utero or during birth. The capsule, which is a polysaccharide coating on the outside of the cell, is considered the most important virulence factor in GBS.Expression of capsule plays a role in evasion of the host immune response to GBS infection. The presence of capsule on GBS depends on the CpsA protein, which is involved in the attachment of capsule to the cell wall. CpsA is a multi-functional protein containing an intracellular domain and two extracellular domains including the accessory and the LytR domains. Previous data demonstrates a small region within the accessory domain of CpsA that, when expressed separately, can have a negative effect on the amount of capsule on the cell. In this study, cell morphology analysis and capsule assays were used to determine the role of the accessory domain on CpsA function and capsule production. The data collected in this study suggest that the accessory domain is important in capsule expression, and without the accessory domain capsule expression cannot be complemented back to WT CpsA levels. In addition, this data shows that the intradomain region plays an important, but unknown role in CpsA function. Finally, for the first time, short chain morphologies were associated with decreased capsule expression.