Multistrain population control systems and methods

1. A method of maintaining a bacterial co-culture, the method comprising:

culturing a first bacterial strain for a first period of time in a growth environment;

adding a second bacterial strain to the growth environment and culturing the second bacterial strain for a second period of time;

adding a third bacterial strain to the growth environment and culturing the third bacterial strain for a third period of time,

wherein each of the first, second, and third bacterial strains comprises a toxin system;

wherein the toxin system of the first bacterial strain produces a first toxin/first antitoxin pair and a third antitoxin from a third toxin/third antitoxin pair wherein the first bacterial strain does not produce the third toxin;

wherein the toxin system of the second bacterial strain produces a second toxin/second antitoxin pair and the first antitoxin from the first toxin/first antitoxin pair wherein the second bacterial strain does not produce the first toxin; and

wherein the toxin system of the third bacterial strain produces a third toxin/third antitoxin pair and the second antitoxin from the second toxin/second antitoxin pair wherein the third bacterial strain does not produce the second toxin, and

wherein each of the first, second, and third bacterial strains comprises

a lysis plasmid having a lysis gene under the control of an activatable promoter; and

an activator plasmid having an activator gene, the expression of which promotes the accumulation of a quorum-sensing molecule,

wherein both the activatable promoter of the lysis gene and the expression of the activator gene is activated by the quorum-sensing molecule.

2. The method of claim 1 , wherein the quorum-sensing molecule is the same in each of the first, second, and third bacterial strains.

3. The method of claim 1 , wherein the toxin system of the first bacterial strain, the second bacterial strain, and the third bacterial strain is independently encoded in a genome of at least one of the first, second, and third bacterial strains, on a plasmid integrated into the genome of at least one of the first, second, and third bacterial strains, on multiple plasmids integrated into the genome of at least one of the first, second, and third bacterial strains, or a combination thereof.

4. The method claim 1 , wherein in each of the at least the first, second, and third bacterial strains the lysis plasmid comprises a lysis gene, an activatable promoter, and a reporter gene; and the activator plasmid comprises an activator gene, a degradation tag, and a reporter gene.

5. The method claim 1 , wherein the lysis gene in each of the at least the first, second, and third bacterial strains is E from a bacteriophage ΦX174.

6. The method claim 1 , wherein the activatable promoter in each of the at least the first, second, and third bacterial strains is a LuxR-AHL activatable luxI promoter and the activator gene is a LuxI.

7. The method claim 1 , wherein one or more of the first, second, and third bacterial strains encodes a heterologous nucleic acid and/or a heterologous protein operably linked to a promoter.

8. The method of claim 7 , wherein the heterologous nucleic acid and/or heterologous protein is a therapeutic agent.

9. The method of claim 8 , wherein the therapeutic agent is selected from the group consisting of: an inhibitory nucleic acid, a cytokine, an enzyme, a peptide hormone, a fusion protein, a clotting factor, a toxin, an antimicrobial peptide, and an antibody or antigen-binding fragment thereof.

10. A method of maintaining a bacterial co-culture, the method comprising:

providing n bacterial strains comprising at least a first bacterial strain, a second bacterial strain, and an n th bacterial strain that are distinct from each other;

co-culturing each of the bacterial strains sequentially for one or more independent periods of time in a growth environment;

wherein n is at least 3;

wherein each of the n bacterial strains comprises a toxin system;

wherein the toxin system of the first bacterial strain produces a first toxin/first antitoxin pair and an n th antitoxin from an n th toxin/n th antitoxin pair, wherein the first toxin is effective against the n th bacterial strain;

wherein the toxin system of the second bacterial strain produces a second toxin/second antitoxin pair and the first antitoxin from the first toxin/first antitoxin pair, wherein the second toxin is effective against the first bacterial strain; and

wherein the toxin system of the first bacterial strain produces an n th toxin/n th antitoxin pair and an n−1 th antitoxin from an n−1 th toxin/n−1 th antitoxin pair, wherein the n th toxin is effective against the n−1 th bacterial strain.

11. The method of claim 10 , wherein the toxin system of the n bacterial strains is independently encoded in a genome of at least one of the first, second, and n th bacterial strains, on a plasmid integrated into the genome of at least one of the first, second, and n th bacterial strains, on multiple plasmids integrated into the genome of at least one of the first, second, and n th bacterial strains, or a combination thereof.

12. The method claim 10 , wherein one or more of the periods of time partially or completely overlap.

13. The method claim 10 , wherein one or more of the n bacterial strains encodes a heterologous nucleic acid and/or a heterologous protein operably linked to a promoter.

14. The method of claim 13 , wherein the heterologous nucleic acid and/or heterologous protein is a therapeutic agent.

15. The method of claim 14 , wherein the therapeutic agent is selected from the group consisting of: an inhibitory nucleic acid, a cytokine, an enzyme, a peptide hormone, a fusion protein, a clotting factor, a toxin, an antimicrobial peptide, and an antibody or antigen-binding fragment thereof.

16. The method claim 10 , wherein each of the second bacterial strain through the nth bacterial strain does not produce the second toxin of the toxin system of the n−1 th strain, and the first bacterial strain does not produce the n th toxin of the toxin system of the n th bacterial strain.