Lactate Dehydrogenase Is the Key Enzyme for Pneumococcal Pyruvate Metabolism and Pneumococcal Survival in Blood

Abstract

Streptococcus pneumoniae is a fermentative microorganism and causes serious diseases in humans, including otitis media, bacteremia, meningitis, and pneumonia. However, the mechanisms enabling pneumococcal survival in the host and causing disease in different tissues are incompletely understood. The available evidence indicates a strong link between the central metabolism and pneumococcal virulence. To further our knowledge on pneumococcal virulence, we investigated the role of lactate dehydrogenase (LDH), which converts pyruvate to lactate and is an essential enzyme for redox balance, in the pneumococcal central metabolism and virulence using an isogenic ldh mutant. Loss of LDH led to a dramatic reduction of the growth rate, pinpointing the key role of this enzyme in fermentative metabolism. The pattern of end products was altered, and lactate production was totally blocked. The fermentation profile was confirmed by in vivo nuclear magnetic resonance (NMR) measurements of glucose metabolism in nongrowing cell suspensions of the ldh mutant. In this strain, a bottleneck in the fermentative steps is evident from the accumulation of pyruvate, revealing LDH as the most efficient enzyme in pyruvate conversion. An increase in ethanol production was also observed, indicating that in the absence of LDH the redox balance is maintained through alcohol dehydrogenase activity. We also found that the absence of LDH renders the pneumococci avirulent after intravenous infection and leads to a significant reduction in virulence in a model of pneumonia that develops after intranasal infection, likely due to a decrease in energy generation and virulence gene expression.

Molecular Characterization of N-glycan Degradation and Transport in Streptococcus pneumoniae and Its Contribution to Virulence

“…To assess the virulence of pneumococcal strains, mice were lightly anesthetized with 3% (v/v) isoflurane over oxygen and an inoculum of 50 μL containing approximately 1 × 10 6 CFU in PBS was given drop-wise into the nostrils as described previously [81, 82]. After infection, the inoculum dose was confirmed by viable counting on blood agar plates to determine the actual administered dose.…”

Biological and Chemical Adaptation to Endogenous Hydrogen Peroxide Production in Streptococcus pneumoniae D39

“…Pyruvate, the end product of glycolysis, is used as a precursor to make acetyl coenzyme A (acetyl-CoA) and acetyl-phosphate (and ultimately ATP), while l -lactate is used to regenerate NAD + via lactate dehydrogenase (Ldh) (Fig. 1) (6). In the presence of molecular oxygen, lactate oxidase (LctO) converts l -lactate to pyruvate and hydrogen peroxide (H 2 O 2 ).…”

The Pneumococcal Surface Proteins PspA and PspC Sequester Host C4-Binding Protein To Inactivate Complement C4b on the Bacterial Surface

“…For this, 200 ng of PCR fragment was mixed with 200 to 400 ng of donor mariner plasmid pR412, conferring resistance to spectinomycin. The mixture was incubated in the presence of Himar1 transposase, as described previously (46,47). Gaps in transposition products were repaired with T4 DNA polymerase (New England BioLabs, Hitchin, UK) and subsequently by E. coli ligase (New England Biolabs).…”