While vital to our quality of life, traditional antibiotics face the serious problems of widespread bacterial resistance and destruction of natural gut flora - problems which call for improved twenty-first century antibiotics. Using synthetic biology tools, we designed, built, and tested two new systems to fight infections by both broad types of bacteria - Gram-positive and Gram-negative. Our first project targets Bacillus anthracis, the Gram-positive pathogen that causes anthrax. We re-engineered an enzyme to remove the pathogen's protective coating, rendering it defenseless against the immune system. In our second project, we re-engineered and transplanted a protein secretion system capable of combating Gram-negative bacteria into E. coli. This system was designed to target Gram-negative pathogens in a modular and controllable fashion. These two systems are the vanguard of a new era of antibiotics using the power of nature harnessed with the tools of synthetic biology.