Pneumococcal carbohydrate transport: food for thought

Abstract

Streptococcus pneumoniae relies exclusively on carbohydrates as a carbon source and devotes 30% of all transport mechanisms to carbohydrate import. Pneumococci utilize at least 32 carbohydrates in vitro; yet, some proposed substrates are not human-derived making it unclear where they are encountered in the host niche while other substrates remain unidentified. The majority of transporter loci are conserved, arguing against redundancy and instead for distinct roles during pathogenesis. Despite this, expression and regulation of carbohydrate transporters in vivo remains ill-defined. Recent work has also demonstrated multiple ABC transporters share an ATPase; whether this evolved for genome minimization or for transporter regulation remains unknown. Continued efforts to understand carbohydrate import may reveal novel vaccine and therapeutic targets and increase understanding of pneumococcal pathogenesis.

Neuraminidase A-Exposed Galactose Promotes Streptococcus pneumoniae Biofilm Formation during Colonization

“…For this reason, a major part of the pneumococcus genome is dedicated toward the uptake and processing of carbohydrates, including sialic acid, galactose, and glucose (23,52). Since the initial discovery that the pneumococcus produces neuraminidase, much effort has gone toward elucidating its role in the disease process (30,34,35,53,54), determining the impact of free sialic acid on the bacterium's metabolism (31,33,55,56), and testing whether inhibition of neuraminidase activity is protective (57).…”

Dynamic Changes in the Streptococcus pneumoniae Transcriptome during Transition from Biofilm Formation to Invasive Disease upon Influenza A Virus Infection

“…Virulent S. pneumoniae upregulated genes involved in uptake and utilization of carbohydrates through glycolysis and other pathways. S. pneumoniae relies solely on carbohydrates as a carbon source (65). S. pneumoniae contains genes encoding at least 20 carbohydrate transporters in the core genome (66) and can ferment Ͼ30 different carbohydrates (67).…”

Sialic Acid-Mediated Gene Expression in Streptococcus pneumoniae and Role of NanR as a Transcriptional Activator of the nan Gene Cluster

“…Metabolic selection enables a bacterium to choose a preferred source of carbon over a nonpreferred one through a mechanism called carbon catabolite repression (CCR) (5). CcpA (carbon catabolite protein A) is a transcription factor that mediates CCR in the presence of a preferred sugar source, e.g., glucose, by binding to catabolite repression elements (cre boxes) found in the promoter regions of CcpA-targeted genes (5,(7)(8)(9). Despite the importance of carbohydrates in the pathogenesis of S. pneumoniae, research concerning metabolic pathways of S. pneumoniae still demands more attention.…”