Reutericyclin is a tetramic acid antibiotic produced by the bacterium Limosilactobacillus reuteri (formerly Lactobacillus reuteri) that has potential use as a food preservative. Reutericyclin is a hydrophobic, negatively charged molecule with the molecular formula C<sub>20</sub>H<sub>31</sub>NO<sub>4</sub>.
Reutericyclin disrupts the cell membrane of sensitive bacteria by acting as a proton ionophore. Reutericyclin has a broad spectrum of activity against Gram-positive bacteria, but has no effect on Gram-negative bacteria because the lipopolysaccharide (LPS) in the outer membrane of Gram-negative bacteria prevents access by hydrophobic compounds.
Reutericyclin is synthesized by some strains of L. reuteri by a 9-gene cluster, containing a polyketide synthase (PKSs) and a non-ribosomal peptide synthetase (NRPS).