Cyanobacteria are the only prokaryotes capable of oxygenic photosynthesis, which have potential to serve as "autotrophic cell factories". However, the synthesis of biofuels and chemicals using cyanobacteria as chassis are suffered from poor stress tolerance and low yield, resulting in low economic feasibility for industrial production. Thus, it's urgent to construct new cyanobacterial chassis by means of synthetic biology. In recent years, adaptive laboratory evolution (ALE) has made great achievements in chassis engineering, including optimizing growth rate, increasing tolerance, enhancing substrate utilization and increasing product yield. ALE has also made some progress in improving the tolerance of cyanobacteria to high light intensity, heavy metal ions, high concentrations of salt and organic solvents. However, the engineering efficiency of ALE strategy in cyanobacteria is generally low, and the molecular mechanisms underpinning the tolerance to various stresses have not been fully elucidated. To this end, this review summarizes the ALE-associated technical strategies and their applications in cyanobacteria chassis engineering, following by discussing how to construct larger ALE mutation library, increase mutation frequency of strains and shorten evolution time. Moreover, exploration of the construction principles and strategies for constructing multi-stress tolerant cyanobacteria, and efficient analysis the mutant libraries of evolved strains as well as construction of strains with high yield and strong robustness are discussed, with the aim to facilitate the engineering of cyanobacteria chassis and the application of engineered cyanobacteria in the future.
Technology ; Photosynthesis/genetics* ; Cyanobacteria/genetics* ; Light ; Biofuels

Biorefinery technologies provide promising solutions to achieve sustainable development facing energy and environment crisis, while abundant sugar feedstock is an essential basis for biorefinery industries. Photosynthetic production of sucrose with cyanobacteria is an alternative sugar feedstock supply route with great potentials. Driven by solar energy, cyanobacteria photosynthetic cell factory could directly convert carbon dioxide and water into sucrose, and such a process could simultaneously reduce carbon emissions and supply sugar feedstocks. Here we introduced the history and updated the state-of-the-art on development of cyanobacteria cell factories for photosynthetic production of sucrose, summarized the progress and problems on mechanisms of sucrose synthesis, metabolic engineering strategies and technology expansions, and finally forecasted the future development direction in this area.
Carbon Dioxide ; Cyanobacteria ; Metabolic Engineering ; Photosynthesis ; Sucrose

Cyanobacteria is one of the promising microbial chassis in synthetic biology, which serves as a typical host for light-driven production. With the gradual depletion of fossil resources and intensification of global warming, the research on cyanobacterial cell factory using CO2 as carbon resource is ushering in a new wave. For a long time, research focus on cyanobacterial cell factory has mainly been the production of energy products, such as liquid fuels and hydrogen. One of the critical bottlenecks occurring in cyanobacterial cell factory is the poor economic performance, which is mainly caused by the inherent inefficiency of cyanobacteria. The problem is particularly prominent for these extremely cost-sensitive energy products. As an indispensable basis for modern industry, polymer monomers belong to the bulk chemicals with high added value. Therefore, increasing attention has been focused on polymer monomers which are superior in overcoming the economic barrier in commercialization of cyanobacterial cell factories. Here, we systematically review the progress on the production of polymer monomers using cyanobacteria, including the strategies for improving production, and the related technologies for the application of this important microbial cell factory. Finally, we summarize several issues in cyanobacterial synthetic biology and proposed future developing trends in this field.
Cyanobacteria ; Macromolecular Substances ; Polymers ; Synthetic Biology

In the forensic practice, the reliability of diatom test as a supportive measure to diagnose drowning is still disputed, from trustworthy to worthless. Some of the reason for the controversy is low sensitivity of the test, possibility of postmortem contamination and the detection of diatom in the tissues of non-drowned body. However, there is a variation of the diatom flora by season and by locale and it is strongly correlated with the frequency of positive diatom test outcomes. Therefore, if there is a profile of the diatom flora at a site, it can be compared with the diatom genera found in tissues of the immersed bodies, and also the test result can be predicted or verified. On each season, at three aquatic locations where drowning victims are often found, the author collected water samples and examined the plankton species of the samples, including dominant species and total number of plankton by site and by season. The examination result showed 16 species of diatoms, 20 species of green algae, 6 species of cyanobacteria, and 6 species of other algae. There is an enormous difference of population of algae by site(39 cells ~ 37,180 cells), but conspicuous periodicity of types and numbers of algae is not noted by season and by depth.
Chlorophyta ; Cyanobacteria ; Diatoms ; Drowning ; Periodicity ; Plankton ; Seasons ; Water

Gas vesicles (GVs) are gas-filled protein nanostructures that can regulate the buoyancy of microorganisms such as cyanobacteria and archaea. Recent studies have shown that GVs have the potential to be used as ultrasound molecular imaging probes in disease diagnosis and treatment. However, the mechanism of the inflation and deflation of GVs remains unclear, which hampers the preservation of GVs and gas replacement. In the present study, the environmental pH value was found to be an important factor in regulating the inflation and deflation of GVs. It can not only regulate the inflation and deflation of GVs in vivo to make Microcystis sp. cells present distinct levitation state, but also regulate the inflation and deflation of purified GVs in vitro, and the regulation process is reversible. Our results may provide a technical support for the large-scale production and preservation of biosynthetic ultrasound molecular imaging probes, especially for gas replacement to meet different diagnostic and therapeutic needs, and would facilitate the application of biosynthetic ultrasound molecular imaging probes.
Cyanobacteria ; Proteins/chemistry* ; Nanostructures/chemistry* ; Molecular Imaging ; Hydrogen-Ion Concentration

Orthogonal combination design was adopted in examining the Spirulina platensis (S. platensis) yield and the influence of four factors (Se content, Se-adding method, S content and NaHCO3 content) on algae growth. The results showed that Se content, Se-adding method and NaHCO3 content were key factors in cultivation conditions of Se-enriched S. platensis with the optimal combination being Se at 300 mg/L, Se-adding amount equally divided into three times and NaHCO3 at 16.8 g/L. Algae yield had a remarkable correlation with OD560 and floating rate by linear regression analysis. There was a corresponding relationship between effects of the four factors on algae yield and on OD560, floating rate too. In conclusion, OD560 and floating rate could be served as yield-forming factors.
Bicarbonates ; analysis ; Culture Media ; Cyanobacteria ; growth & development ; Selenium ; analysis ; pharmacology

Gas vesicles are a unique class of gas-filled protein nanostructures which are commonly found in cyanobacteria and Halobacterium. The gas vesicles may scatter sound waves and generate harmonic signals, which enabled them to have the potential to become a novel ultrasound contrast agent. However, the current hypertonic cracking method for isolating gas vesicles contains tedious operational procedures and is of low yield, thus not suitable for large-scale application. To overcome these technical challenges, we developed a rapid and efficient method for isolating gas vesicles from Microcystis. The new H₂O₂-based method increased the yield by three times and shortened the operation time from 24 hours to 7 hours. The H₂O₂ method is not only suitable for isolation of gas vesicles from laboratory-cultured Microcystis, but also suitable for colonial Microcystis covered with gelatinous sheath. The gas vesicles isolated by H₂O₂ method showed good performance in ultrasound contrast imaging. In conclusion, this new method shows great potential for large-scale application due to its high efficiency and wide adaptability, and provides technical support for developing gas vesicles into a biosynthetic ultrasonic contrast agent.
Contrast Media ; Cyanobacteria ; Hydrogen Peroxide ; Microcystis ; Proteins/chemistry*

Bronchial asthma can be triggered by microbial agents in the oropharynx. This study was designed to identify the differences in microbiota of oropharynx of bronchial asthmatic patients in contrast to normal controls. In order to resolve the qualitative and quantitative diversity of the 16S rRNA gene present in the oropharynx microbiota of 4 patients and 4 controls, we compared microbial communities using Sanger sequencing and 376 sequences of 16S rRNA gene were analyzed. Of the total microbial diversity detected in the oropharynx in asthmatic patients 45.6% comprised members of the Firmicutes. In contrast, Proteobacteria (44.0%) dominated the oropharyngeal microbiota in the normal control group. Members of the Bacteroidetes, Fusobacteria, Actinobacteria, TM7, Cyanobacteria and unclassified bacteria were present in both groups. In conclusion, the difference in the microbiota of the oropharynx between patients and normal individuals could trigger symptomatic attacks in bronchial asthma.
Actinobacteria ; Asthma* ; Bacteria ; Bacteroidetes ; Cyanobacteria ; Fusobacteria ; Genes, rRNA ; Humans ; Metagenome ; Microbiota* ; Oropharynx ; Proteobacteria

The present study was undertaken to explore the inhibitory effect of cyanobacterial extracts of Nostoc commune FA-103 against the tomato-wilt pathogen, Fusarium oxysporum f. sp. lycopersici. In an optimal medium, cell growth, antifungal activity, and antifungal compound production could be increased 2.7-fold, 4.1-fold, and 13.4-fold, respectively. A crude algal extract had a similar effect as mancozeb at the recommended dose, both in laboratory and pot tests. In vitro and in vivo fungal growth, spore sporulation and fungal infection of wilt pathogen in tomato seeds were significantly inhibited by cyanobacterial extracts. Nostoc commune FA-103 extracts have potential for the suppression of Fusarium oxysporum f. sp. lycopersici.
Azepines ; Cyanobacteria ; Fluoroquinolones ; Fusarium ; Lycopersicon esculentum ; Maneb ; Nostoc commune ; Seeds ; Spores ; Zineb

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*