Decreased light-harvesting antenna size in cyanobacteria

Abstract

The invention provides methods and compositions for increasing photosynthetic efficiency and biomass production in cyanobacterial cultures by minimizing the phycobilisome light-harvesting antenna size through disruption of the phycocyanin-encoding CPC-operon.

What is claimed is: 
     
       1. A method of enhancing biomass accumulation of a cyanobacteria culture, the method comprising:
 providing a cyanobacteria cell population comprising cyanobacteria that are genetically modified in the genome to have a disruption in an endogenous CPC-operon comprising genes encoding CPCA, CPCB, CPCC1, CPCC2, and CPCD polypeptide components of phycocyanin-containing rods, wherein the disruption decreases phycobilisome antenna size compared to counterpart wild-type cyanobacteria comprising a native CPC-operon; 
 growing the cyanobacterial cell population in a reactor to obtain a cyanobacterial culture; 
 maintaining the cyanobacteria culture under conditions in which the photosynthetically active radiation (PAR) intensity is at least 500 micromol photons per square meter per second; and the culture absorbs at least 70% of the incoming light. 
 
     
     
       2. The method of  claim 1 , wherein the PAR intensity is at least 800 micromol photons per square meter per second. 
     
     
       3. The method of  claim 1 , wherein the culture absorbs at least 80%, or at least 90% of the incoming light. 
     
     
       4. The method of  claim 1 , wherein the disruption in the endogenous CPC-operon is inhibition of a CPCA and/or CPCB gene. 
     
     
       5. The method of  claim 1 , wherein the disruption in the endogenous CPC-operon is inhibition of at least one of a CPCC1, CPCC2, or CPCD gene. 
     
     
       6. The method of  claim 1 , wherein the disruption in the endogenous CPC-operon is a deletion of at least one of a CPCA, CPCB, CPCC1, CPCC2, or CPCD genes. 
     
     
       7. The method of  claim 1 , wherein the cyanobacteria are a species of a genus selected from the group consisting of  Synechocystis, Synechococcus, Cyanothece , and  Thermosynechococcus.    
     
     
       8. The method of  claim 1 , wherein the cyanobacteria are a species of a genus of filamentous cyanobacteria. 
     
     
       9. The method of  claim 8 , wherein the genus is selected from the group consisting of  Arthrospira, Nostoc , and  Anabaena.    
     
     
       10. The method of  claim 1 , wherein the disruption is deletion of the endogenous CPC-operon. 
     
     
       11. The method of  claim 1 , wherein the disruption in the endogenous CPC-operon comprises deletion of a CPCA or CPCB gene. 
     
     
       12. The method of  claim 1 , wherein the endogenous CPC-operon encodes a CPCA polypeptide that has at least 70% identity to the amino acid sequence of SEQ ID NO:2 or encodes a CPCB polypeptide that has at least 70% identity to SEQ ID NO:3.