Impact of Modified Lactoperoxidase Systems on Glycolytic Metabolism and Virulence Factors in Streptococcus mutans

TL;DR

This study shows that iodide-based lactoperoxidase systems can reduce harmful bacterial metabolism and virulence in Streptococcus mutans, a key contributor to tooth decay.

Contribution

The study reveals that iodide-based LpoS systems uniquely disrupt S. mutans metabolism and virulence compared to other variants.

Findings

LpoS-I− significantly reduced atpD and ldh gene expression and impaired acid tolerance in S. mutans.

LpoS-I− inhibited pyruvate accumulation, indicating altered glycolytic flux.

LpoS-SCN− and LpoS-SeCN− also downregulated virulence genes but had less impact on acid production.

Abstract

The lactoperoxidase system (LpoS) is an enzymatic antimicrobial mechanism of saliva that oxidizes (pseudo)halide substrates to reactive compounds capable of limiting microbial growth. This study evaluated how different LpoS variants—utilizing iodide (LpoS-I−), thiocyanate (LpoS-SCN−), selenocyanate (LpoS-SeCN−), and a thiocyanate–iodide mixture (LpoS-SCN− + I−)—affect virulence, metabolism, and biofilm structure in Streptococcus mutans. Using qRT-PCR, pyruvate assays, MTT reduction, and confocal microscopy, we found that LpoS-I− most effectively reduced atpD and ldh expression, impaired acid tolerance, and decreased lactate and pyruvate production. LpoS-SCN− and LpoS-SeCN− also downregulated atpD and gtfB, although LpoS-SeCN− upregulated ldh. Despite minimal structural biofilm disruption, LpoS-I− markedly inhibited intracellular and extracellular pyruvate accumulation, suggesting altered glycolytic flux. These findings indicate that iodide-based LPO systems modulate key metabolic and regulatory pathways in S. mutans and may hold potential for inclusion in anticaries oral formulations.

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