Cristian studies the waterborne human pathogen Vibrio cholerae, the microbe responsible for Cholera, a devastating and often fatal disease. His work is focused on the chemical weapons that V. cholerae use against other bacteria so as to dominate their local environment. Cristian discovered that human-derived strains of V. cholerae can have anti-bacterial weapons that are in addition to those of strains isolated from environmental sources. Building on this work, Cristian showed that one of the newly discovered anti-bacterial weapons of V. cholerae acts by permeabilizing the cell membranes of other bacteria. Additionally, Cristian and his collaborators showed how other bacteria can guard against attack by V. cholerae. This fundamental research could be of great importance for understanding the virulence of pathogenic V. cholerae.