Microcins are small antibacterial peptides whose narrow spectrum allows only target pathogens to be killed within a microbiome, reducing the chances that resistance will arise. Due to this specific activity, microcins make ideal candidates for defense against bacterial diseases that infect hosts with essential, diverse microbiomes. However, most of the known and characterized microcins target E. coli and its close relatives leaving a large realm left to be explored for microcins that kill pathologically relevant bacteria. Here I screen for putative microcin sequences in plant pathogens (Pantoea, Erwinia, and Xanthomonas species) using a bioinformatics pipeline, clone these sequences into a modular secretion system, and test their efficacy against E. coli and Pantoea strains. Five novel microcin sequences were found within the Pantoea genus and two microcins within the Erwinia genus that inhibited E. coli growth. My work establishing an effective pipeline to discover and test novel microcins can help further studies that seek to understand microbiome dynamics and develop therapeutics.