Nucleic acid systems that enable bacteria to specifically target solid tumors via glucose-dependent viability

A method of constructing a bacterial strain that is genetically engineered, the method comprising:

• generating a random library of a nucleic acid system by inserting a random sequence that consists of 5-6 nucleotides to replace original or native nucleotides of the bacterial strain that are located immediately upstream of a second DNA fragment;
• inserting, into the bacterial strain, the nucleic acid system that includes:
• a first DNA fragment that encodes a toxin gene that expresses a toxin that kills the bacterial strain;
• the second DNA fragment that encodes an antidote gene that expresses an antidote that negates the toxin;
• a first promoter that controls transcription of the antidote gene, such that glucose represses the transcription of the antidote gene;
• and
• a first constitutive promoter that causes constitutive expression of the toxin gene;
• and
• the random sequence that consists of 5-6 nucleotides and that replaces the original or native 5-6 nucleotides of the bacterial strain located immediately upstream of the second DNA fragment;
• culturing clones of the bacterial strain that includes the nucleic acid system;
• and
• selecting the clones that grow in the absence of glucose but do not grow in the presence of glucose at a concentration equal or higher than 1 mM, thereby obtaining the bacteria strain that is genetically engineered and targets solid tumors;
• and
• wherein a pair of the toxin and the antidote is selected from a group consisting of a CcdB-CcdA pair, an AvrRxo1-Arc1 pair, an Hha-TomB pair, and a PaaA2-ParE2 pair.