Cyanobacteria having improved photosynthetic activity
Inventors
Roberts, James • Carleton, Michael • CARRIERI, Damian • Hickman, Jason W.
Assignees
Publication Number
US-9914907-B2
Publication Date
2018-03-13
Expiration Date
2034-03-10
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Abstract
This disclosure describes modified photosynthetic microorganisms, including Cyanobacteria, that have a reduced amount of a light harvesting protein (LHP) and contain one or more introduced or overexpressed polynucleotides encoding one or more enzymes associated with lipid biosynthesis, and which are capable of producing increased amounts of fatty acids and/or synthesizing triglycerides.
Core Innovation
The invention relates to genetically modified Cyanobacteria that exhibit increased photosynthetic activity through specific genetic modifications involving the NbIA gene. The core approach is to either add an endogenous or exogenous NbIA gene or to add a promoter that regulates NbIA gene expression in Cyanobacteria. These genetic alterations result in increased levels of NbIA polypeptide or a biologically active fragment thereof containing a conserved domain, leading to an enhanced level of photosynthetic activity and a reduced amount of light harvesting protein (LHP) compared to wild-type Cyanobacteria.
The modified Cyanobacteria generated through this method demonstrate distinct characteristics: they display enhanced photosynthetic activity, reduced levels of light harvesting proteins such as phycobilisomes and phycobiliproteins, increased proteolytic degradation of phycobilisomes, and higher growth or division rates. These effects can be achieved by techniques such as addition of an NbIA gene, introduction of an inducible or constitutive promoter, or replacement of the native promoter of the NbIA gene.
The central problem addressed is the saturation of light harvesting protein capacity in Cyanobacteria, which limits the efficiency of using light for photosynthesis under culture conditions. By reducing the level of light harvesting proteins and increasing NbIA protein activity—achieved through genetic modifications—the invention enables improved photosynthetic activity and higher yield of desired metabolites under various growth conditions, overcoming limitations observed with wild-type organisms.
Claims Coverage
The patent presents three primary inventive features centered on genetically modifying Cyanobacteria to enhance photosynthetic activity by manipulating the NbIA gene and related elements.
Genetic modification involving NbIA gene or its regulatory elements in Cyanobacteria
A cell culture is comprised of modified Cyanobacteria with a genetic modification including at least one of: - Addition of an endogenous NbIA gene - Addition of an exogenous NbIA gene - Addition of a promoter that regulates NbIA gene expression This results in changes compared to wild-type Cyanobacteria: - Increased levels of NbIA polypeptide or biologically active fragment including a conserved domain - Enhanced level of photosynthetic activity - Reduced amount of light harvesting protein (LHP)
Method for generating modified Cyanobacteria via NbIA gene modification or promoter addition
A method is disclosed which involves modifying Cyanobacteria by adding an endogenous NbIA gene, adding an exogenous NbIA gene, or adding a promoter that regulates NbIA gene expression. This modification leads to: - Increased level of NbIA polypeptide or biologically active fragment compared to wild-type Cyanobacteria - Enhanced photosynthetic activity compared to wild-type Cyanobacteria - Reduced amount of light harvesting protein (LHP) compared to wild-type Cyanobacteria
Modified Cyanobacterium with altered NbIA expression leading to increased photosynthetic activity and reduced LHP
A modified Cyanobacterium is claimed, comprising at least one of: - Addition of an endogenous NbIA gene - Addition of an exogenous NbIA gene - Addition of a promoter that regulates NbIA gene expression Where this genetic modification results in: - Increased levels of NbIA polypeptide or active fragment with a conserved domain - Enhanced level of photosynthetic activity - Reduced amount of light harvesting protein (LHP) compared with wild-type Cyanobacterium
In sum, the inventive features cover specific genetic interventions to increase NbIA expression or regulate it in Cyanobacteria, directly resulting in heightened photosynthetic activity and diminished light harvesting proteins.
Stated Advantages
The modified Cyanobacteria demonstrate increased levels of photosynthetic activity relative to corresponding wild-type strains.
The modifications result in enhanced growth rate or division rate in Cyanobacteria as compared to wild-type organisms.
There is a reduced amount of light harvesting proteins (such as phycobilisomes or phycobiliproteins) in the modified Cyanobacteria.
The reduction in light harvesting proteins is accompanied by increased proteolytic degradation of phycobilisomes.
Documented Applications
Use of the modified Cyanobacteria as a feedstock in the production of biofuels, including biodiesel.
Production of specialized chemicals such as glycerin and wax esters using the modified Cyanobacteria.
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