Antibacterial effectors in Dictyostelium discoideum: specific activity against different bacterial species

Dictyostelium discoideum is a phagocytic amoeba continuously eating, killing and digesting bacteria. Previous studies have detected in D. discoideum cell extracts a bacteriolytic activity effective against Klebsiella pneumoniae bacteria. In this study we characterized bacteriolytic activities found in D. discoideum cell extracts against five different bacteria (K. pneumoniae, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus subtilis). We first analyzed the bacteriolytic activity against these five bacteria in parallel over a range of pH values. We then measured the remaining bacteriolytic activity in D. discoideum kil1 and modA KO mutants. We also performed partial fractionation of D. discoideum extracts and assessed activity against different bacteria. Together our results indicate that optimal bacteriolytic activity against different bacteria results from the action of different effectors. Proteomic analysis allowed us to propose a list of potential bacteriolytic effectors. IMPORTANCEMany antibacterial effectors have been characterized over the last decades, and their biological importance, mode of action and specificity is often still under study. Here we characterized in vitro bacteriolytic activity in D. discoideum extracts against five species of gram-negative and gram-positive bacteria. Our results reveal that optimal lysis of different bacteria mobilizes different effectors. Proteomic analysis generated a list of potential bacteriolytic effectors. This work opens the way for future analysis of the role of individual effectors in living D. discoideum cells.