Butyrate kinase (Buk) links branched-chain fatty acid biosynthesis, cold adaptation, and pathogenesis in Listeria monocytogenes

We constructed in-frame deletion mutants of ptb and buk in L. monocytogenes F2365 and found that Buk, but not Ptb, is required for anteiso-BCFA biosynthesis and cold tolerance. The buk mutant displayed reduced anteiso-BCFAs and a shift in phosphatidylglycerol (PG) composition, indicating substantial membrane remodeling.

Functionally, the buk mutant exhibited defects in cell-to-cell spread, intracellular replication, phospholipase activity, LLO production, and in vivo virulence, whereas ptb retained wild-type phenotypes. Transcriptomic profiling revealed coordinated metabolic reprogramming in the buk mutant, characterized by downregulation of branched-chain amino acid (BCAA) biosynthesis and phosphotransferase (PTS) systems, indicating impaired precursor supply and nutrient acquisition, along with compensatory upregulation of central metabolism and redox processes.