The expansive effects of polyamines on the metabolism and virulence of Streptococcus pneumoniae

Abstract

Polyamines are common intracellular metabolites of nearly all cells, and their conservation across a vast diversity of cells suggests critical roles for these compounds in cellular physiology. Most intracellular polyamines are associated with RNA and, subsequently, polyamines have significant effects on transcription and translation. Putrescine and spermidine are the most common polyamines in bacteria. Intracellular polyamine pools in bacteria are tightly controlled by both de novo synthesis and transport. Polyamine homeostasis is emerging as a critical parameter of multiple pathways and physiology with substantial impact on bacterial pathogenesis, including the important human pathogen Streptococcus pneumoniae. Modulation of polyamine metabolism in pneumococci is an important regulator of central metabolism. It has broad effects on virulence factors such as capsule as well as stress responses that ultimately impact the survival of pneumococcus in a host. Polyamine transport protein as a single antigen or in combination with other pneumococcal proteins is shown to be an efficacious immunogen that protects against nasopharyngeal colonization, and invasive disease. A comprehensive description of polyamine metabolic pathways and their intersection with pneumococcal pathogenesis will undoubtedly point to novel approaches for treatment and prevention of pneumococcal disease.

Keywords: Autolysis; Capsule; Immunization; Pneumococci; Polyamine; PotD; Stress response; Virulence.

Fig. 1

Structures of polyamines most commonly found in prokaryotes

Fig. 2

Central common polyamine synthesis pathways in prokaryotes. ADC – arginine decarboxylase, ARG – arginase, ODC – ornithine decarboxylase, AGM – agmatinase, ADI – agmatine deiminase, NCPAH – N-carbamoylputrescine amidohydrolase, CASDH – carboxyspermidine dehydrogenase, CASDC – carboxyspermidine decarboxylase, PAPT – polyamine aminopropyltransferase, MAT – methionine adenosyltransferase, SAMDC – S-adenosylmethionine decarboxylase, LDC – lysine decarboxylase; AdoMet – S-adenosylmethionine, AdoMetDC – decarboxylated S-adenosylmethionine