Elucidating the Capacity and Mechanism of <i>Lactiplantibacillus plantarum</i> in Synthesizing Essential Amino Acids from Non-Essential Amino Acids in a Novel Severely Deficient Medium
2025
Tran Quang Duc | Takashi Uebanso | Kazuaki Mawatari | Akira Takahashi
The gut microbiota plays a vital role in human physiology and nutrient metabolism. However, its capacity to synthesize essential amino acids (EAAs) as a nutrient source remains insufficiently characterized, with genomic evidence suggesting this potential but lacking direct in vitro validation. To address this, we developed an artificial medium comprising 78 components, enabling <i>Lactiplantibacillus plantarum</i> (ATCC 8014) to achieve growth comparable to that in conventional MRS broth. Through systematic depletion of individual and multiple EAAs, leucine, isoleucine, phenylalanine, tryptophan, and valine were identified as critical for the survival and proliferation of this strain. Subsequent analysis revealed that lysine and threonine were synthesized and secreted into the medium after 48 h of culturing in medium lacking these EAAs, using aspartic acid as a major precursor. Notably, in response to methionine deficiency, cysteine seemed to be converted to methionine via the transsulfuration pathway, with vitamin B6 serving as an essential cofactor. Collectively, our findings demonstrated the ability of <i>L. plantarum</i> to synthesize and provide lysine and threonine in these EAA-restricted conditions. This ability to serve EAAs to the environment provides a basis for future studies to further investigate the role of intestinal microbiota as a potential source of EAAs in host animals.
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