The Effect of Impaired Polyamine Transport on Pneumococcal Transcriptome

Abstract

Infections due to Streptococcus pneumoniae, a commensal in the nasopharynx, still claim a significant number of lives worldwide. Genome plasticity, antibiotic resistance, and limited serotype coverage of the available polysaccharide-based conjugate vaccines confounds therapeutic interventions to limit the spread of this pathogen. Pathogenic mechanisms that allow successful adaption and persistence in the host could be potential innovative therapeutic targets. Polyamines are ubiquitous polycationic molecules that regulate many cellular processes. We previously reported that deletion of polyamine transport operon potABCD, which encodes a putrescine/spermidine transporter (∆potABCD), resulted in an unencapsulated attenuated phenotype. Here, we characterize the transcriptome, metabolome, and stress responses of polyamine transport-deficient S. pneumoniae. Compared with the wild-type strain, the expression of genes involved in oxidative stress responses and the nucleotide sugar metabolism was reduced, while expression of genes involved in the Leloir, tagatose, and pentose phosphate pathways was higher in ΔpotABCD. A metabolic shift towards the pentose phosphate pathway will limit the synthesis of precursors of capsule polysaccharides. Metabolomics results show reduced levels of glutathione and pyruvate in the mutant. Our results also show that the potABCD operon protects pneumococci against hydrogen peroxide and nitrosative stress. Our findings demonstrate the importance of polyamine transport in pneumococcal physiology that could impact in vivo fitness. Thus, polyamine transport in pneumococci represents a novel target for therapeutic interventions.

Impact of Difluoromethylornithine and AMXT 1501 on Gene Expression and Capsule Regulation in Streptococcus pneumoniae

“…Metabolomics studies support the notion that polyamines could exert control over capsule synthesis at the transcriptional level [18]. Deletion of the polyamines transport operon (∆potABCD) resulted in a noticeable decrease in intracellular polyamine levels [19] and an increase in susceptibility to oxidative and nitrosative stress [20]. Similar to the SP_0916 deletion, there was an upregulation in the expression of genes associated with the PPP and the arginine deiminase system as an adaptive mechanism to manage stress conditions in ∆potABCD [20].…”

The oxidative stress response of Streptococcus pneumoniae: its contribution to both extracellular and intracellular survival

“…The potABCD mutant exhibits heightened vulnerability to oxidative stress, akin to the cadA mutant, due to a notable decline in polyamine and trehalose levels, which serve as antioxidants. Metabolomics analysis further elucidated that the potABCD mutant displays diminished glutathione levels, providing additional evidence to support its observed phenotype ( Nakamya et al, 2021 ).…”

“…Transcriptomic and proteomic analysis determined that this mutation negatively affects the expression of various genes known to be essential for OSR, including tpxD and htrA . Additionally, the authors propose that SpeA not only regulates the synthesis of glutathione but also influences the endogenous production of H 2 O 2 ( Nakamya et al, 2021 ). The speA mutation also leads to an increase in carbon flow through the pentose phosphate pathway (PPP), which is considered a cellular response to oxidative stress.…”

Exogenous glycogen utilization effects the transcriptome and pathogenicity of Streptococcus suis serotype 2

“…Glucose is preferentially catabolized by the glycolysis pathway and to a minor extent by PPP in S. suis , which mainly provides intermediates needed for anabolic reactions ( Willenborg et al., 2015 ). The metabolic shift toward the PPP and reduced amino acid production usually represent the cellular responses to increased stresses ( Nakamya et al., 2021 ). Increased activity of the PPP will reduce the energy-consumption through the glycolysis pathway and rapidly meet the cellular demand for NADH/NADPH to combat oxidative stress ( Nakamya et al., 2021 ).…”

“…The metabolic shift toward the PPP and reduced amino acid production usually represent the cellular responses to increased stresses ( Nakamya et al., 2021 ). Increased activity of the PPP will reduce the energy-consumption through the glycolysis pathway and rapidly meet the cellular demand for NADH/NADPH to combat oxidative stress ( Nakamya et al., 2021 ). Our data showed that the central metabolism shifts from the glycolysis pathway toward the PPP in S. suis after glycogen induction ( Figure 3 ) and presents the possible stress responses of S. suis under glycogen-induced conditions.…”