Fuente: WIPO "tomato" Tumor-selective expression of therapeutic molecules by bacteria is achieved by one or more AND, NOR, OR, NOT and/or NAND gate genetic circuits. The therapeutic molecules can be proteins, metabolites or catabolites, and may also be immunotherapeutics or immunotherapeutic cytotoxins. Single or multiple expression components may be used. Tumor selective expression of multimeric proteins utilizes multimerization as to complete the genetic circuit. Genetic circuits that are unlinked, function to achieve a combined effect on specificity of delivery of antitumor therapeutic molecules. Compositions and methods to generate silica, PEG and Poly-HPMA coated bacteria are also provided. Compositions and methods for selectively sensing or imaging tumors are also described.