Molecular switches
Genetically modified microorganisms that have the ability to convert carbon substrates into chemical products such as 2,3-BDO; 1,4-BDO; isobutyraldehyde; isobutanol; 1-butanol; n-butanol; ethanol; fatty alcohols; and fatty acid methyl ester are disclosed. For example, genetically modified methanotrophs that are capable of generating 2,3-BDO; 1,4-BDO; isobutyraldehyde; isobutanol; 1-butanol; n-butanol; ethanol; fatty alcohols; and fatty acid methyl ester at high titers from a methane source are disclosed. Methods of making these genetically modified microorganisms and methods of using them are also disclosed. These microorganisms and methods make use of molecular switches to regulate gene expression.
1. A genetically modified microorganism capable of converting a C1 carbon to a multicarbon product, the microorganism comprising a heterologous gene under the control of a promoter that is responsive to a rare earth metal.
2. The genetically modified microorganism of claim 1 , wherein expression of the heterologous gene is repressed by a rare earth metal.
3. The genetically modified microorganism of claim 1 , wherein the genetically modified microorganism is a methanotroph.
4. The genetically modified microorganism of claim 1 , wherein the heterologous gene encodes acetolactate synthase, alpha-acetolactate decarboxylase, acetoin reductase, or any combination thereof.
5. A method of making a multicarbon product from a C1 carbon, the method comprising:
a) contacting the genetically modified microorganism of claim 1 with a C1 carbon; and
b) growing the microorganism to produce the multicarbon product.
6. The method of claim 5 , wherein the multicarbon product is: 2,3-butanediol; 1,4-butanediol; isobutyraldehyde; isobutanol; 1-butanol; n-butanol; ethanol; fatty (or aliphatic long chain) alcohols; fatty acid methyl esters; or any combination thereof.
7. The method of claim 5 , wherein the C1 carbon is methane.
8. The method of claim 5 , further comprising recovering the multicarbon product.
9. The method of claim 5 , further comprising contacting the microorganism with media having a rare earth metal that can activate or repress the promoter.
10. The method of claim 9 , wherein the rare earth metal is cerium (Ce), dysprosium (Dy), erbium (Er), europium (Eu), gadolinium (Gd), holmium (Ho), lanthanum (La), lutetium (Lu), neodymium (Nd), praseodymium (Pr), promethium (Pm), samarium (Sm), scandium (Sc), terbium (Tb), thulium (Tm), ytterbium (Yb), or yttrium (Y).
11. The method of claim 10 , wherein the rare earth metal is lanthanum (La).
12. The method of claim 11 , wherein the lanthanum (La) is present at a concentration of at least 0.5 μM.
13. A method of altering the expression of a gene or set of genes within the genetically modified microorganism of claim 1 , the method comprising contacting the genetically modified microorganism with a rare earth metal, wherein the gene or set of genes is/are comprised in a heterologous polynucleotide comprising a promoter that is responsive to the rare earth metal.
14. The genetically modified microorganism of claim 1 , wherein the promoter is a pMxaF1 promoter.
15. The genetically modified microorganism of claim 1 , wherein the heterologous gene encodes an acetolactate synthase comprising an amino acid sequence that is at least 80% identical to any one of SEQ ID NOs: 1, 3, 5, and 29.
16. The genetically modified microorganism of claim 1 , wherein the heterologous gene encodes an alpha-acetolactate decarboxylase comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 7 or 9.
17. The genetically modified microorganism of claim 1 , wherein the heterologous gene encodes an acetoin reductase comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 11.