Pseudomonas aeruginosa kill the host Drosophila melanogasger very rapidly due to bacteria fitness in vivo. However, mutant of antitoxin HigA has impaired virulence accompanying with loss of fitness. We suppose the free toxin HigB in higA mutant inhibits some proteins production as to be an RNase. To explore the mechanism of antitoxin HigA leading to bacteria fitness in Drosophila, we performed proteomics to analyze the differential proteins in higA mutant in vitro.