A new study has revealed how a widely used food bacterium manages its internal chemistry to survive and thrive. The discovery could pave the way for greener, cheaper vitamin production for food and health industries.<\/p>\n
Vitamin K\u2082, or menaquinone, plays a key role in bone health, blood clotting and cardiovascular function. It is produced naturally by certain bacteria, including Lactococcus lactis, a staple of dairy fermentation.<\/p>\n
This microbe generates an unstable intermediate compound essential to all forms of vitamin K\u2082. But it makes only enough to support its own growth, preventing a toxic buildup.<\/p>\n
This natural self-limiting system poses a challenge to those trying to engineer bacteria to produce more vitamins. Microbes tend to cap production at self-sustaining levels, slowing commercial applications.<\/p>\n
Engineering them to make extra vitamins could replace energy-intensive chemical synthesis or plant extraction, but scientists must first understand the production \u201cbrakes\u201d built into their biology.<\/p>\n
\u201cVitamin-producing microbes could transform nutrition and medicine, but we must first decode their inherent checks and balances,\u201d said Caroline Ajo-Franklin, co-corresponding author of the study and director of the Rice Synthetic Biology Institute.<\/p>\n
She said their work shows how L. lactis fine-tunes its supply, creating an opening for precision genetic rewiring.<\/p>\n
Tracking hard-to-detect compound<\/p>\n
The research team combined biosensing, genetic engineering, and mathematical<\/a> modelling to study the process.<\/p>\n Because the vitamin K\u2082 precursor is difficult to measure, they built a highly sensitive biosensor in a different bacterium. The device is thousands of times more sensitive than conventional tools and requires little lab equipment.<\/p>\n Researchers then altered enzyme levels in the vitamin\u2019s biosynthetic pathway and measured output under different conditions. These results fed into a mathematical model. At first, the model assumed an unlimited supply of starting material, but the predictions did not match lab results.<\/p>\n \u201cOnce we allowed for depletion of the starting substrate, the model output matched our experimental data,\u201d said Oleg Igoshin, co-corresponding author. It became clear that production hit a ceiling when the substrate ran low, like trying to bake more cookies with extra trays but without enough flour.<\/p>\n Gene order shapes production limits<\/p>\n The team found another control layer in the order of enzyme-encoding genes on DNA<\/a>. Rearranging these genes changed how much of the intermediate compound the cells produced. <\/p>\n This suggests an evolutionary mechanism that controls production in ways not fully understood before.<\/p>\n \u201cBy tuning substrate supply, enzyme expression and gene order simultaneously, we can push production above the natural ceiling,\u201d said first author Siliang Li, now a postdoctoral fellow at Rice.<\/p>\n Boosting L. lactis output could enable more efficient fermentation<\/a> processes and even probiotic supplements that deliver higher vitamin K\u2082 doses. <\/p>\n Co-first author Jiangguo Zhang said greater efficiency could reduce feedstock needs and lab space, lowering costs for fortified foods and supplements.<\/p>\n