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  • The growth benefits and toxicity of quinone biosynthesis are balanced by a dual regulatory mechanism and substrate limitations
Title: The growth benefits and toxicity of quinone biosynthesis are balanced by a dual regulatory mechanism and substrate limitations
ABSTRACT Quinones play a central role in maintaining redox balance and conserving energy but can trigger oxidative stress at high levels. However, the mechanisms by which microbes regulate quinone levels remain poorly understood, hindering effective metabolic engineering to modulate microbes for quinone production. Here, we show that the biosynthesis of the menaquinone precursor 1,4-dihydroxy-2-naphthoic acid (DHNA) in the lactic acid bacteriumLactococcus lactisis regulated by a combined genetic, enzymatic, and metabolic mechanism. Using synthetic biology approaches, we found that enzymes MenF and MenD both contribute to DHNA regulation, with MenD playing a more prominent role in controlling DHNA concentrations. A mathematical model elucidates a two-phase regulatory pattern resulting from the interplay of reversible flux and allosteric feedback inhibition, where either MenF or MenD can serve as the regulatory enzyme, depending on their relative expression ratio. In addition, the overproduction of DHNA is constrained by substrate availability, ensuring a sufficient but not excessive DHNA level to benefit cell growth while mitigating cytotoxicity. Collectively, these mechanisms maintain a fine-tuned physiological quinone level and suggest that modulating substrate supplement and MenF-to-MenD ratio could be keys for engineering DHNA production. IMPORTANCEQuinones are crucial molecules in cellular respiration, helping cells produce energy and maintain balance in their redox state. However, excessive quinone levels can be toxic, making it vital for microbes to tightly regulate their production. Our study uncovers howLactococcus lactis, a key food fermenting bacterium, uses a multi-layer mechanism to maintain optimal levels of the menaquinone precursor 1,4-dihydroxy-2-naphthoic acid (DHNA). By combining biosensors, genetic perturbations, and modeling, we show how cells balance the benefits and toxicity of quinones. These findings not only reveal fundamental microbial physiology but also provide strategies to engineer microbes for improved quinone production.  more » « less
Award ID(s):
1856742 2019745
PAR ID:
10660855
Author(s) / Creator(s):
; ; ;
Editor(s):
Newman, Dianne K
Publisher / Repository:
ASM
Date Published:
Journal Name:
mBio
Volume:
16
Issue:
9
ISSN:
2150-7511
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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