It can be useful to regulate the growth of microbial cells. Some embodiments herein provide genetically engineered microbial cells that can produce bacteriocins to control the growth of microbial cells. In some embodiments microbial cells are contained within a desired environment. In some embodiments contaminating microbial cells are neutralized. In some embodiments a first microbial cell type regulates the growth of a second microbial cell type so as to maintain a desired ratio of the two cell types.
