Streptococcus agalactiae MprF synthesizes a novel cationic glycolipid and contributes to brain entry and meningitis

Group B Streptococcus (GBS) is a major human pathogen, causing meningitis and severe infection in newborns, yet little is known about its lipid membrane. Here, we investigated the GBS lipid membrane and identify a novel cationic glycolipid, lysyl-glucosyl-diacylglycerol (Lys-Glc-DAG). Multiple peptide resistance factor (MprF) is highly conserved in many bacterial pathogens and plays a critical role in resistance against cationic antimicrobial peptides, cationic bacteriocins, and antibiotics. The MprF protein has been shown to catalyze the amino-acylation of the anionic phospholipid phosphatidylglycerol (PG). Most notably, MprF uses L-lysyl-tRNA to esterify PG with a positively charged lysine to produce lysyl-phosphatidylglycerol (Lys-PG). We demonstrate through heterologous host expression and gene deletion that the GBS MprF has an expanded substrate repertoire and is the biosynthetic enzyme responsible for both Lys-Glc-DAG and Lys-PG biosynthesis in GBS. Furthermore, we demonstrate that MprF contributes specifically to meningitis pathogenesis at the blood-brain barrier both in vitro and in an in vivo hematogenous murine infection model but does not contribute to bloodstream survival. These results greatly expand our knowledge of MprF functions and reveal insights into the survival mechanisms and pathogenesis of meningitis caused by GBS.