Complex microbial communities that populate surfaces of higher organisms such as plants critically impact health of their host by either fighting disease, promoting it or even causing disease. How, why and when communities shift from one state to the other is crucial to develop synthetic microbial communities that can be used as plant protective agents. The goal of DeCoCt is therefore to dissect, design and reconstitute microbial communities form natural field data that are competitive to natural communities and capable of reverting a disease causing community into a protective.