The capsular polysaccharide (CPS) of Streptococcus pneumoniae is largely diverse, and a major contributor to this, is the plethora of glycosyltransferases (GTs) that are present in the CPS synthesis pathway. GTs are enzymes that transfer sugars from an activated sugar donor to a wide range of acceptors. My work mainly focuses on studying the GT specificity, by using S. pneumoniae as our model organism, and aim to assist glycoengineering efforts to generate molecules with desired sugar composition and linkages.