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Abstract Cyanobacteria are important primary producers, contributing to 25% of the global carbon fixation through photosynthesis. They serve as model organisms to study the photosynthesis, and are important cell factories for synthetic biology. To enable efficient genetic dissection and metabolic engineering in cyanobacteria, effective and accurate genetic manipulation tools are required. However, genetic manipulation in cyanobacteria by the conventional homologous recombination-based method and the recently developed CRISPR-Cas gene editing system require complicated cloning steps, especially during multi-site editing and single base mutation. This restricts the extensive research on cyanobacteria and reduces its application potential. In this study, a highly efficient and convenient cytosine base editing system was developed which allows rapid and precise C → T point mutation and gene inactivation in the genomes of Synechocystis and Anabaena. This base editing system also enables efficient multiplex editing and can be easily cured after editing by sucrose counter-selection. This work will expand the knowledge base regarding the engineering of cyanobacteria. The findings of this study will encourage the biotechnological applications of cyanobacteria.

In oligotrophic oceans, primary productivity is widely limited by nitrogen bioavailability. The broadly distributed and abundant nitrogen-fixing cyanobacterium Trichodesmium plays an important role in the oceanic nitrogen and carbon cycles by providing a “new” source of nitrogen to many non-diazotrophic microbes, thereby driving new primary production in the ocean. However, the underlying process and mechanism of nitrogen supply from Trichodesmium to other phytoplankton remain unclear. Here, our results demonstrated that the fixed nitrogen released by Trichodesmium could sustain the growth of a non-nitrogen-fixing cyanobacterium Synechococcus sp. PCC 7002, including a mutant strain (Mut-ureA) that cannot use urea. However, the growth rate of Mut-ureA was approximately 20% lower than that of the wild strain when Trichodesmium filtrate was used for nitrogen supply. This result was consistent with the composition of the Trichodesmium exudate, in which urea comprised more than 20% of the total fixed nitrogen that was released. It is evident from the experiments that a fraction of the Trichodesmium-derived nitrogen was not available to Mut-ureA. Our results suggested that Trichodesmium produces dissolved organic nitrogen, especially a certain amount of urea as a “new” nitrogen source, benefiting in particular populations of surrounding phytoplankton species.

Abstract Background HIV testing and early linkage to care are critical for reducing the risk of HIV transmission. HIV self-testing (HIVST) is a useful tool for increasing HIV testing frequency.This study aimed to investigate HIVST rates among men who have sex with men (MSM), the characteristics of MSM who had HIVST, and factors associated with HIVST uptake among MSM in Ningbo, China. Methods A cross-sectional study was conducted from April to October 2019 in Ningbo,China. Participants were aged at least 18 years and having had sexual contact with men in the past year. Proportions were used for categorical variables. Adjusted Odds Ratio (AOR) and 95% Confidence Interval (CI) for characteristics associated with HIVST uptake was processed by multivariable logistic regression models. Results Among a sample of 699 MSM recruited, 38.2% had reported previous use of an HIV self-test kit. A greater proportion of HIVST users had a higher frequency of HIV testing (≥ 2 times: 70.0% versus 41.2%, p

In order to improve the management of nitrogen (N) fertilization in pear orchards, we investigated the effects of application timing on the distribution, storage, and remobilization of N in mature pear trees in a field experiment at Jingtai County, Gansu Province, China. Nine trees were selected for the experiment and each received equal aliquots of 83.33 g N in the autumn, spring, and summer, with 15N-labeled (NH4)2SO4 used in one of the aliquots each season. Results showed that the (15N H4)2SO4 applied in the autumn remained in the soil during the winter. In the following spring this N was absorbed and rapidly remobilized into each organ, especially new organs (leaves, fruit and new shoots). The 15N supplied in spring was rapidly transported to developing fruit between the young fruit and fruit enlargement stages. 15N from the summer application of fertilizer was mainly stored in the coarse roots over the winter, then was mobilized to support growth of new organs in spring. In conclusion, for pear trees we recommend that the autumn application of N-fertilizer be soon after fruit harvest in order to increase N stores in fine roots. Spring application should be between full bloom and the young fruit stages to meet the high N demands of developing fruit. Summer application of fertilizer at the fruit enlargement stage does not contemporaneously affect the growth of pears, but increases the N stored in coarse roots, and in turn the amount available for remobilization in spring.

Primary productivity in the nutrient-poor subtropical ocean gyres depends on new nitrogen inputs from nitrogen fixers that convert inert dinitrogen gas into bioavailable forms. Temperature and iron (Fe) availability constrain marine nitrogen fixation, and both are changing due to anthropogenic ocean warming. We examined the physiological responses of the globally important marine nitrogen fixer, Crocosphaera watsonii across its full thermal range as a function of iron availability. At the lower end of its thermal range, from 22 to 27°C, Crocosphaera growth, nitrogen fixation, and Nitrogen-specific Iron Use Efficiencies (N-IUEs, mol N fixed hour–1 mol Fe–1) increased with temperature. At an optimal growth temperature of 27°C, N-IUEs were 66% higher under iron-limited conditions than iron-replete conditions, indicating that low-iron availability increases metabolic efficiency. However, Crocosphaera growth and function decrease from 27 to 32°C, temperatures that are predicted for an increasing fraction of tropical oceans in the future. Altogether, this suggests that Crocosphaera are well adapted to iron-limited, warm waters, within prescribed limits. A model incorporating these results under the IPCC RCP 8.5 warming scenario predicts that Crocosphaera N-IUEs could increase by a net 47% by 2100, particularly in higher-latitude waters. These results contrast with published responses of another dominant nitrogen fixer (Trichodesmium), with predicted N-IUEs that increase most in low-latitude, tropical waters. These models project that differing responses of Crocosphaera and Trichodesmium N-IUEs to future warming of iron-limited oceans could enhance their current contributions to global marine nitrogen fixation with rates increasing by ∼91 and ∼22%, respectively, thereby shifting their relative importance to marine new production and also intensifying their regional divergence. Thus, interactive temperature and iron effects may profoundly transform existing paradigms of nitrogen biogeochemistry and primary productivity in open ocean regimes.

AIM: To evaluate the therapeutic effect of fluorofenidone on disrupted blood-retinal barrier in the diabetic mice and uncover its underlying mechanism. METHODS: db/db mice were randomly chosen for treatment with daily doses of fluorofenidone or placebo at 5-week-old, treatment continued until mice reach 24-week-old. Then, expression of transcriptiona factor insulin gene enhancer binding protein-1 (Islet-1) and vascular endothelial growth factor (VEGF) in murine retinas were evaluated. Retinal vascular permeability was assessed by examining the level of albumin in db/db murine retinas. Furthermore, the retinal vessel tight junction was estimated by checking the level of occludin in the murine retinal tissues. RESULTS: After occurrence of diabetic retinopthy in db/db mice, expressions of transcritpional factor Islet-1 was found to be upregulated in db/db murine retinas compared with non-diabetic controls. Similar to expression pattern of Islet-1, VEGF were also demonstrated to be increased in retinas of db/db mice, which was accompanied by increased retinal vascular leakage and decreased tight junction protein level. Systemetic administration of fluorofenidone repaired broken retinal vascular tight junction by restoring occludin expression in db/db retinal tissue. Consequently, retinal vascular premeability were indicated to be reduced by examining the transudative albumin level in diabetic retinal tissues. Both Islet-1 and VEGF expression were inhibited in the retinas of db/db mice after treatment with fluorofenidone. CONCLUSION: Fluorofenidone significantly protectes retinal tight junction and reduces retinal vascular leakage. The phenomenon can be partially attributed to reducing overexpression of Islet-1 and VEGF in diabetic retinal tissues.

The aim of the present study was to evaluate the efficacy and safety of the treatment of myopic foveoschisis patients using the macular buckling with L-shaped titanium plate and silicon sponge combined with vitrectomy. The data of the patients who underwent macular buckling combined with vitrectomy was collected. The study recorded the following parameters: best corrected visual acuity (BCVA), axial length, intraocular pressure, central macular thickness, and the position of the titanium plate. Following the surgery, the BCVA of the included patients were improved, whereas the axial lengths were reduced followed by resolution of the foveoschisis compared with that noted prior to the operations. All patients had orbital CT examination and the results indicated that the titanium plates were appropriately placed and were not in contact with the optic nerve. Therefore, it is effective to treat myopic foveaschisis by macular buckling using the L-shaped titanium plate and silicon sponge in the presence of vitrectomy.

AIM: To evaluate the expression of transcriptional factor Islet-1 in retina in experimental retinal neovascularization induced by oxygen. METHODS: The murine retinal neovascularization were induced by hyperoxia exposure.The morphological observation of retinal neovascularization was performed using angiography by fluorescein dextran injection under the fluorescence microscope, and the new blood vessels were quantified after 5d in room air(17-day-old)by counting the vascular epithelial cell nuclei protruding into viteous cavity using HE stain. Realtime PCR and Western blot were used to examine retinal Islet-1 level in postnatal 7,12, 14,17 and 26d respectively.RESULTS: A lots of new blood vessels were demonstrated in the mouse retina in hyperoxic group by fluorescein angiography and histological method. Moreover, no significant difference was found in retinal Islet-1 level in postnatal 7d between hyperoxic group and control group, but was significantly higher in postnatal 12, 14 and 17d mice compared with control mice. However, mice at postnatal 26d, expression of Islet-1 in retina decreased to normal level. CONCLUSION: In processing mouse model of retinal neovascularization, sustained hypoxia retinal tissue induce retinal neovascularization by increas the expression of transcription factor Islet-1.

AIM: To compare the differences of tilt and decentration of two aspheric posterior chamber intraocular lens(PC-IOL)implantation by ultrasonic biomicroscope(UBM). METHODS:Thirty-seven patients(45 eyes)underwent cataract surgery were distributed to two groups randomly. Group A was implanted with Akreos AO(Bausch & Lomb; four-haptic)while group B implanted with ZCB00(Abbott Medical Optics, Inc. AMO; two-haptic). All eyes underwent standard phacoemulsification with intraocular lens implantation. Diameter of capsulotomy was recorded. One month postoperatively, vision, best-corrected visual acuity(BCVA)assessment, slit lamp examination, and anterior chamber depth(ACD)measured by UBM were performed. Tilt and decentration were measured horizontally and vertically, and total tilt and decentration were calculated by geometry method.RESULTS:No statistical difference was found in BCVA and diameter of capsulotomy between two groups(P>0.05). The mean ACD of group A and group B were 3.86mm±0.31mm and 4.14mm±0.31mm respectively, which showed it had statistically significant difference(PP>0.05). CONCLUSION:Two-haptic IOL shows no difference in tilt and decentration with four-haptic IOL postoperatively.

AIM:To evaluate the effect and safety of phacoemulsification and intraocular lens implantation combined with trabeculectomy for primary angle-closured glaucoma with cataract.METHODS: Retrospective study was performed in 49 cases(59 eyes)of primary angle-closure glaucoma with cataract patients treated with phacoemulsification and intraocular lens implantation combined with trabeculectomy. Among them, 35 eyes were acute primary angle-closure glaucoma(APACG), 24 eyes were chronic primary angle-closure glaucoma(CPACG).Visual acuity, intraocular pressure(IOP), thickness of lens, axial length of eyeball, central anterior chamber depth, complications and medications were detected in all patients followed up until 6-12 months.RESULTS: 1)Preoperative and postoperative IOP were 23.9±6.6mmHg, 11.7±2.6mmHg respectively in APACG group(n=35, Pn=24, PPPPPPCONCLUSION:Phacoemulsification and intraocular lens implantation combined with trabeculectomy is effective and safe treatment for primary angle-closure glaucoma with cataract patients, especially for acute primary angle-closure glaucoma compared with chronic primary angle-closure glaucoma.

Mitochondrial ribosomal proteins are important for mitochondrial-encoded protein synthesis and mitochondrial function. In addition to their roles in mitoribosome assembly, several mitochondrial ribosome proteins are also implicated in cellular processes like cell cycle regulation, apoptosis, and mitochondrial homeostasis regulation. Here, we demonstrate that MRPL10 regulates cyclin B1/Cdk1 (cyclin-dependent kinase 1) activity and mitochondrial protein synthesis in mammalian cells. In Drosophila, inactivation of mRpL10 (the Drosophila ortholog of mammalian MRPL10) in eyes results in abnormal eye development. Furthermore, expression of human cyclin B1 suppresses eye phenotypes and mitochondrial abnormality of mRpL10 knockdown Drosophila. This study identified that the physiological regulatory pathway of MRPL10 and providing new insights into the role of MRPL10 in growth control and mitochondrial function. [ABSTRACT FROM AUTHOR]

The complex dynamics of the logistic map via two periodic impulsive forces is investigated in this paper. The influences of the system parameter and the impulsive forces on the dynamics of the system are studied respectively. With the parameter varying, the system produces the phenomenon such as periodic solutions, chaotic solutions, and chaotic crisis. Furthermore, the system can evolve to chaos by a cascading of period-doubling bifurcations. The Poincaré map of the logistic map via two periodic impulsive forces is constructed and its bifurcation is analyzed. Finally, the Floquet theory is extended to explore the bifurcation mechanism for the periodic solutions of this non-smooth map. [ABSTRACT FROM AUTHOR]

Cyanobacteria are important players in the global carbon cycle, accounting for approximately 25% of global CO2 fixation. Their CO2-concentrating mechanisms (CCMs) are thought to play a key role in cyanobacterial calcification, but the mechanisms are not completely understood. In Synechocystis sp. strain PCC 6803, a single Ca2+/H+ exchanger (Slr1336) controls the Ca2+/H+ exchange reaction. We knocked out the exchanger and investigated the effects on cyanobacterial calcification and CCMs. Inactivation of slr1336 significantly increased the calcification rate and decreased the zeta potential, indicating a relatively stronger Ca2+-binding ability. Some genes encoding CCM-related components showed increased expression levels, including the cmpA gene, which encodes the Ca2+-dependent HCO3- transporter BCT1. The transcript level of cmpA in the mutant was 30 times that in wild type. A Western blot analysis further confirmed that protein levels of CmpA were higher in the mutant than the wild type. Measurements of inorganic carbon fluxes and O2 evolution proved that both the net HCO3- uptake rate and the BCT1 transporter supported photosynthetic rate in the slr1336 mutant were significantly higher than in the wild type. This would cause the mutant cells to liberate more OH- ions out of the cell and stimulate CaCO3 precipitation in the microenvironment. We conclude that the mutation of the Ca2+/H+ exchanger in Synechocystis promoted the cyanobacterial calcification process by upregulating CCMs, especially the BCT1 HCO3- transporter. These results shed new light on the mechanism by which CCM-facilitated photosynthesis promotes cyanobacterial calcification. [ABSTRACT FROM AUTHOR]

This study investigated the replacement of soybean meal by cottonseed meal in diets for the Chinese mitten crab, Eriocheir sinensis. Seven isocaloric and isonitrogenous diets were tested with five replicates of each treatment. Cottonseed meal replaced 33%, 66%, or 100% of the soybean meal in three diets, while lysine was added to another three containing the same amounts of cottonseed meal. The control contained neither cottonseed meal nor lysine. Protein digestibility decreased with the increase of dietary cottonseed meal and was significantly lower in the 100% treatment than in the control. Dry matter in the body of crabs fed the 33%, 66%, 100%, and 33%+lysine diets was significantly lower than that of the control. Whole body protein decreased as the cottonseed meal content increased, and was significantly lower in crabs fed the 100% diet than in control crabs. Crabs fed the control diet contained higher lipid than those fed other diets, while crabs fed diets containing lysine had significantly lower lipid than crabs fed the 33% diet. Crabs fed the 100%+lysine diet had a significantly higher ash content than those fed the 33% or 100% diets. In conclusion, this study indicates that 66% of soybean meal can be replaced by cottonseed meal in crab diets and 100% of soybean meal can be replaced by cottonseed meal when supplemented by lysine. [ABSTRACT FROM AUTHOR]

As an important metal oxide, anatase titanium dioxide has been widely investigated because of its many promising properties for catalysis and photocatalysis. The properties of anatase TiO2crystals are largely determined by external surfaces exposed. Many efforts have been made to improve the percentage of high-reactive facets like {001} facets of anatase TiO2to enhance its catalytic properties. This review reports the recent progress in designing and fabricating high-reactive facets dominated anatase TiO2viavarious strategies including traditional vapor phase epitaxial processes, hydrothermal/solvothermal methods, nonhydrolytic alcoholysis methods and high temperature gas phase reactions. Furthermore, focusing on the (001) surface, the article also covers advances in the theoretic simulations of various high-reactive facets of anatase TiO2crystals. Finally, we offer a summary and some perspectives on the challenges and new directions for future research in this emerging frontier. [ABSTRACT FROM AUTHOR]

Cyanobacteria use a series of adaptation strategies and a complicated regulatory network to maintain intracellular iron (Fe) homeostasis. Here, a global activator named IutR has been identified through three-dimensional chromosome organization and transcriptome analysis in a model cyanobacterium Synechocystis sp. PCC 6803. Inactivation of all three homologous IutR-encoding genes resulted in an impaired tolerance of Synechocystis to Fe deficiency and loss of the responses of Fe uptake-related genes to Fe-deplete conditions. Protein-promoter interaction assays confirmed the direct binding of IutR with the promoters of genes related to Fe uptake, and chromatin immunoprecipitation sequencing analysis further revealed that in addition to Fe uptake, IutR could regulate many other physiological processes involved in intracellular Fe homeostasis. These results proved that IutR is an important transcriptional activator, which is essential for cyanobacteria to induce Fe-deficiency response genes. This study provides in-depth insights into the complicated Fe-deficient signaling network and the molecular mechanism of cyanobacteria adaptation to Fe-deficient environments. [ABSTRACT FROM AUTHOR]

Marine cyanobacteria contribute to approximately half of the ocean primary production, and their biomass is limited by low iron (Fe) bioavailability in many regions of the open seas. The mechanisms by which marine cyanobacteria overcome Fe limitation remain unclear. In this study, multiple Fe uptake pathways have been identified in a coastal strain of Synechococcus sp. strain PCC 7002. A total of 49 mutants were obtained by gene knockout methods, and 10 mutants were found to have significantly decreased growth rates compared to the wild type (WT). The genes related to active Fe transport pathways such as TonB-dependent transporters and the synthesis and secretion of siderophores are found to be essential for the adaptation of Fe limitation in Synechococcus sp. PCC 7002. By comparing the Fe uptake pathways of this coastal strain with other open-ocean cyanobacterial strains, it can be concluded that the Fe uptake strategies from different cyanobacteria have a strong relationship with the Fe bioavailability in their habitats. The evolution and adaptation of cyanobacterial iron acquisition strategies with the change of iron environments from ancient oceans to modern oceans are discussed. This study provides new insights into the diversified strategies of marine cyanobacteria in different habitats from temporal and spatial scales. [ABSTRACT FROM AUTHOR]

Cyanobacteria are foundational drivers of global nutrient cycling with high intracellular iron (Fe) requirements. Fe is found at extremely low concentrations in aquatic systems however, and the ways in which cyanobacteria take up Fe are largely unknown, especially the initial step in Fe transport across the outer membrane. Here, we identified one TonB protein and four TonB-dependent transporters (TBDTs) of the energy-requiring Fe acquisition system and six porins of the passive diffusion Fe uptake system in the model cyanobacterium Synechocystis sp. PCC 6803. The results experimentally demonstrated that TBDTs not only participated in organic ferri-siderophore uptake, but also in inorganic, free Fe (Fe') acquisition. 55Fe uptake rate measurements showed that a TBDT quadruple mutant acquired Fe at a slower rate than the wild type and lost nearly all ability to take up ferri-siderophores, indicating that TBDTs are critical for siderophore uptake. However, the mutant retained the ability to take up Fe' at 42% of the wild type Fe' uptake rate, suggesting additional pathways of Fe' acquisition besides TBDTs, likely by porins. Mutations in four of the six porin-encoding genes produced a low- Fe-sensitive phenotype, while mutation in all six genes was lethal to cell survival. These diverse outer membrane Fe uptake pathways reflect cyanobacterial evolution and adaptation under a range of Fe regimes across aquatic systems. [ABSTRACT FROM AUTHOR]