Antibacterial effectors in <i>Dictyostelium discoideum</i> : specific activity against different bacterial species

<i>Dictyostelium discoideum</i> is a phagocytic amoeba continuously eating, killing, and digesting bacteria. Previous studies have detected in <i>D. discoideum</i> cell extracts a bacteriolytic activity effective against <i>Klebsiella pneumoniae</i> bacteria. In this study, we characterized bacteriolytic activities found in <i>D. discoideum</i> cell extracts against five different bacteria (<i>K. pneumoniae</i>, <i>Escherichia coli</i>, <i>Pseudomonas aeruginosa</i>, <i>Staphylococcus aureus</i>, and <i>Bacillus subtilis</i>). 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 <i>D. discoideum kil1</i> and <i>modA</i> knockout mutants. We also performed partial fractionation of <i>D. discoideum</i> 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 past decades, and their biological importance, mode of action, and specificity are often still under study. Here we characterized <i>in vitro</i> bacteriolytic activity in <i>D. discoideum</i> 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 <i>D. discoideum</i> cells.