Cyclo(L-Phe-L-Val) is a diketopiperazine metabolite first isolated from a marine bacteria, Pseudoalteromonas sp. in 2011. Cyclo(L-Phe-L-Val) is also produced as a secondary metabolite of Streptomyces rutgerensis and Bacillus subtilis. Limited bioassay data suggests cyclo(L-Phe-L-Val) acts as a quorum sensing regulator but does not itself exhibit antimicrobial activity. Exogenously added cyclo(L-Phe-L-Val) may induce Pseudoalteromonas sp. to produce antibacterial products under low cell density conditions. It appears to act by stimulating the bacteria to induce metabolite production.