Proton-pumping rhodopsin (PPR) is a simple photosystem widely distributed in nature. By binding to retinal, PPR can transfer protons from the cytoplasmic to the extracellular side of the membrane under illumination, creating a proton motive force (PMF) to synthesize ATP. The conversion of light into chemical energy by introducing rhodopsin into nonphotosynthetic engineered strains could contribute to promoting growth, increasing production and improving cell tolerance of microbial hosts. Gloeorhodopsin (GR) is a PPR from Gloeobacter violaceus PCC 7421. We expressed GR heterologously in Escherichia coli and verified its functional activity. GR could properly function as a light-driven proton pump and its absorption maximum was at 539 nm. We observed that GR was mainly located on the cell membrane and no inclusion body could be found. After increasing expression level by ribosome binding site optimization, intracellular ATP increased, suggesting that GR could supply additional energy to heterologous hosts under given conditions.
Cyanobacteria/metabolism* ; Escherichia coli/metabolism* ; Proton Pumps ; Rhodopsin/metabolism* ; Rhodopsins, Microbial/metabolism*

Cyanobacteria are important photosynthetic autotrophic microorganisms and are considered as one of the most promising microbial chassises for photosynthetic cell factories. Glycogen is the most important natural carbon sink of cyanobacteria, playing important roles in regulating its intracellular carbon distributions. In order to optimize the performances of cyanobacterial photosynthetic cell factories and drive more photosynthetic carbon flow toward the synthesis of desired metabolites, many strategies and approaches have been developed to manipulate the glycogen metabolism in cyanobacteria. However, the disturbances on glycogen metabolism usually cause complex effects on the physiology and metabolism of cyanobacterial cells. Moreover, the effects on synthesis efficiencies of different photosynthetic cell factories usually differ. In this manuscript, we summarized the recent progress on engineering cyanobacterial glycogen metabolism, analyzed and compared the physiological and metabolism effects caused by engineering glycogen metabolism in different cyanobacteria species, and prospected the future trends of this strategy on optimizing cyanobacterial photosynthetic cell factories.
Carbon/metabolism* ; Carbon Dioxide/metabolism* ; Cyanobacteria/metabolism* ; Glycogen/metabolism* ; Metabolic Engineering ; Photosynthesis/physiology*

Carboxysomes are extremely efficient microcompartments committed to CO2 fixation due to tailored CO2-concentrating mechanism (CCM). In cyanobacteria and some chemoautotrophs, carboxysomes as organelle-like microbodies encapsulate ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) and carbonic anhydrase (CA). Together with active inorganic carbon uptake transporters, carboxysomes accumulate HCO3(-) in the cytoplasm, leading to high efficiency of carbon fixation. Based on the elucidation of structures and functionalities, heterologous production of carboxysomes has been achieved so far. In fact, the genes encoding either vacant carboxysome shell or only interior components have been characterized. This review summarizes the discovery along with types, showcases molecular structures and roles of carboxysomes in CCM, and presents their broad applications in metabolic engineering.
Biological Transport ; Carbon ; metabolism ; Carbon Cycle ; Carbon Dioxide ; metabolism ; Cyanobacteria ; metabolism ; Metabolic Engineering

The aquatic ferns of the genus Azolla are nitrogen-fixing plants that have great potentials in agricultural production and environmental conservation. Azolla in many aspects is qualified to serve as a model organism for genomic studies because of its importance in agriculture, its unique position in plant evolution, its symbiotic relationship with the N2-fixing cyanobacterium, Anabaena azollae, and its moderate-sized genome. The goals of this genome project are not only to understand the biology of the Azolla genome to promote its applications in biological research and agriculture practice but also to gain critical insights about evolution of plant genomes. Together with the strategic and technical improvement as well as cost reduction of DNA sequencing, the deciphering of their genetic code is imminent.
Cyanobacteria ; genetics ; Ferns ; Genes, Plant ; Genome, Plant ; Genomics ; methods ; Nitrogen ; metabolism ; Plants ; genetics ; Sequence Analysis, DNA

Phycoerythrocyanin(PEC) lyase-isomerase PecE/PecF from Mastigocladus laminosus is the specific enzyme for biosynthesis of PEC alpha-subunit(alpha-PEC). In this work, the specificity of PecE/PecF on substrate apoproteins was reported. PecE/PecF could catalyse the reconstitution of phycocyanobilin(PCB) with apoproteins of alpha-PEC from two different subspecies of Mastigocladus laminosus, as well the site-directed mutated apoprotein of alpha-PEC with Trp at 128 to Phe in vitro, but could not catalyse the reconstitution of PCB with apoprotein of phycocyanin alpha-subunit(alpha-CPC) from Mastigocladus laminosus. The surfactant Triton X-100 had no effect for the reconstitution of alpha-PEC, while it could improve the reconstitution of PCB with apoprotein of alpha-CPC.
Apoproteins ; metabolism ; Bacterial Proteins ; Catalysis ; Cyanobacteria ; enzymology ; Light-Harvesting Protein Complexes ; Lyases ; metabolism ; Octoxynol ; pharmacology ; Proteins ; metabolism ; Substrate Specificity

The cyanobacterial circadian clock has three relatively independent parts: the input path, the core oscillator, and the output path. The core oscillator is composed of three clock proteins: KaiA, KaiB, and KaiC. The interactions among these three proteins generate a rhythmic signal and convey the input signals to the output signals to maintain the accuracy and stability of the oscillation of downstream signals. Based on the cyanobacterial circadian clock and the structure, function, and interaction of the clock proteins of the core oscillator, combining the recent results from our laboratory, this review summarized the recent progresses of the molecular mechanism of KaiA in regulating KaiC's enzymatic activity, mediating phase reset of the oscillator, and competing with CikA for the binding site of KaiB.
Bacterial Proteins ; genetics ; metabolism ; Circadian Clocks ; genetics ; Circadian Rhythm Signaling Peptides and Proteins ; metabolism ; Cyanobacteria ; genetics ; Enzyme Activation ; genetics

The world's energy and global warming crises call for sustainable, renewable, carbon-neutral alternatives to replace fossil fuel resources. Currently, most biofuels are produced from agricultural crops and residues, which lead to concerns about food security and land shortage. Compared to the current biofuel production system, cyanobacteria, as autotrophic prokaryotes, do not require arable land and can grow to high densities by efficiently using solar energy, CO(2), water, and inorganic nutrients. Moreover, powerful genetic techniques of cyanobacteria have been developed. For these reasons, cyanobacteria, which carry out oxygenic photosynthesis, are attractive hosts for production of fuels and chemicals. Recently, several chemicals including ethanol, isobutanol and isoprene have been produced by engineered cyanobacteria directly using solar energy, CO(2), and water. Cyanobacterium is therefore a potential novel cell factory for fuels and chemicals production to address global energy security and climate change issues.
Biofuels ; Butadienes ; Butanols ; metabolism ; Carbon Dioxide ; metabolism ; Cyanobacteria ; genetics ; growth & development ; metabolism ; radiation effects ; Ethanol ; metabolism ; Genetic Engineering ; methods ; Hemiterpenes ; biosynthesis ; Pentanes ; Photosynthesis ; Sunlight ; Water ; metabolism

Attempts were made to culture Spirulina platensis in human urine directly to achieve biomass production and O(2) evolution, for potential application to nutrient regeneration and air revitalization in life support system. The culture results showed that Spirulina platensis grows successfully in diluted human urine, and yields maximal biomass at urine dilution ratios of 140 approximately 240. Accumulation of lipid and decreasing of protein occurred due to N deficiency. O(2) release rate of Spirulina platensis in diluted human urine was higher than that in Zarrouk medium.
Biomass ; Bioreactors ; microbiology ; Cell Culture Techniques ; methods ; Cell Proliferation ; Cyanobacteria ; growth & development ; metabolism ; Life Support Systems ; Oxygen ; isolation & purification ; metabolism ; Urine ; microbiology

OBJECTIVETo study the protective effects of polysaccharide of Spirulina platensis and Sargassum thunbeergii on vascular of alloxan (ALX) induced diabetic rats.

METHODWith the doses of polysaccharide of Spirulina platensis (PSP) and Sargassum thunbeergii (PST) compound (1:1) 12.261, 36.783, 110.349 mg x kg(-1) by i.g. administration to alloxan induced diabetic rats respectively for 6 weeks. Then the blood glucose and the TC, HDL-C, TG, NO, ET in serum were detected. The contraction and relaxation response to NE and ACh in aortic rings of the alloxan induced diabetic rats has been studied.

RESULTThe results showed the compound of PSP and PST could decrease the blood glucose and the TC, TG, NO, ET in serum and increase HDL-C than in the alloxan induced diabetic rats. The contraction responses to NE in aortic rings of the alloxan induced diabetic rats were significantly elevated in the normal rats, and the responses to ACh were significantly lower. PSP and PST compound could significantly lower the responses to NE and significantly elevate the responses to ACh in aortic rings of the alloxan induced diabetic rats.

CONCLUSIONPSP and PST compound could decrease blood glucose and could protect the vascular of alloxan induced diabetic rats.

Animals ; Aorta, Thoracic ; drug effects ; Blood Glucose ; metabolism ; Cholesterol ; blood ; Cholesterol, HDL ; blood ; Cyanobacteria ; chemistry ; Diabetes Mellitus, Experimental ; blood ; Endothelins ; blood ; Female ; Male ; Mice ; Muscle Contraction ; drug effects ; Muscle, Smooth, Vascular ; drug effects ; Nitric Oxide ; blood ; Polysaccharides ; isolation & purification ; pharmacology ; Polysaccharides, Bacterial ; isolation & purification ; pharmacology ; Protective Agents ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Sargassum ; chemistry ; Triglycerides ; blood