Fragments of -thymosin from the sea urchinParacentrotus lividus as potential antimicrobial peptidesagainst staphylococcal biofilms

The immune mediators in echinoderms can be a potential source of novel antimicrobial peptides (AMPs) appliedtoward controlling pathogenic staphylococcal biofilms that are intrinsically resistant to conventional antibiotics.The peptide fraction <5 kDa from the cytosol of coelomocytes of the sea urchin Paracentrotus lividus (5-CC)was tested against a group of Gram-positive and Gram-negative pathogen reference strains. The 5-CC of P. lividuswas active against all planktonic-tested strains but also showed antibiofilm properties against staphylococcal strains.Additionally,wedemonstrated the presenceof three smallpeptides in the5-CCbelonging tosegment 9-41of aP. lividus -thymosin. The smallest of these peptides in particular, showed the common chemical–physical characteristics ofAMPs. This novel AMP from -thymosin has high potential activity as an antibiofilm agent, acting on slow-growingbacterial cells that exhibit a reduced susceptibility to conventional antibiotics and represent a reservoir for recurrentbiofilm-associated infections.