New antimicrobial peptides from Tirmania pinoyi and Terfezia boudieri in the struggle against antibiotic resistance

Antibiotic resistance of common pathogenic microorganisms is a topic of great concern that has finally received media attention and entered into the political agenda of world leaders. Drug-resistant bacteria are cause of thousands of deaths worldwide, then there is an urgent need for new antimicrobials, otherwise we risk losing the ability to control effectively the infectious diseases. Such emergence can be faced looking also at not usual source of antimicrobial agents, for example medicinal mushrooms. With the objective to tackle Gram-positive and Gram-negative pathogens, we focused on two edible desert truffles mushrooms Tirmania pinoyi and Terfezia boudieri as origin of new antimicrobial peptides (AMPs), active not only against free-living microorganisms (planktonic), but also against complex communities of pathogens (biofilms) that are intrinsically resistant to conventional antibiotics. In particular, in vitro antibacterial activity of acid-soluble protein extracts (aqueous extracts) of the two above-mentioned species were investigated against two important human pathogenic reference strains Staphylococcus aureus ATCC 29213 and Pseudomonas aeruginosa ATCC 15442. The acid-soluble protein extracts peptide fractions (<5kDa) of T pinoyi and T. boudieri showed minimum inhibitory concentrations of 50 μg/ml against tested pathogens. In order to characterize the peptide fraction components, a nano RPHPLC/nESI-MS/MS analysis was performed using a Thermo Scientific Dionex UltiMate 3000 RSLCnano system coupled on-line with a Thermo Fisher Scientific Orbitrap Fusion Tribrid® (Q-OT-qIT) mass spec-trometer. Peptide and protein identification was obtained by searching LC/MS/MS data against the “Fungi” Swiss-Prot database using the PEAKS de novo sequencing software. From acquired in silico data, at least four of ten identified peptides, due to their similarity in the sequences with previously described peptides and ability to interact with membranes, are potential AMPs. We believe our preliminary results promising to obtain valuable AMPs to fight pathogens such as S. aureus e P. aeruginosa of a great clinical importance, very common in hospital settlement, but also in animal health and in the field of food safety.