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1.
J Cell Biol ; 221(2)2022 02 07.
Artigo em Inglês | MEDLINE | ID: mdl-34817556

RESUMO

Ferroptosis is an oxidative and iron-dependent form of regulated cell death (RCD) recently described in eukaryotic organisms like animals, plants, and parasites. Here, we report that a similar process takes place in the photosynthetic prokaryote Synechocystis sp. PCC 6803 in response to heat stress. After a heat shock, Synechocystis sp. PCC 6803 cells undergo a cell death pathway that can be suppressed by the canonical ferroptosis inhibitors, CPX, vitamin E, Fer-1, liproxstatin-1, glutathione (GSH), or ascorbic acid (AsA). Moreover, as described for eukaryotic ferroptosis, this pathway is characterized by an early depletion of the antioxidants GSH and AsA, and by lipid peroxidation. These results indicate that all of the hallmarks described for eukaryotic ferroptosis are conserved in photosynthetic prokaryotes and suggest that ferroptosis might be an ancient cell death program.


Assuntos
Cianobactérias/citologia , Cianobactérias/metabolismo , Ferroptose , Ferro/metabolismo , Antioxidantes/metabolismo , Ácido Ascórbico/metabolismo , Cálcio/metabolismo , Caspase 3/metabolismo , Caspase 7/metabolismo , Citosol/metabolismo , Glutationa/metabolismo , Resposta ao Choque Térmico , Lipidômica , Lipídeos/química , Oxirredução , Espécies Reativas de Oxigênio/metabolismo , Synechocystis/metabolismo , Tilacoides/metabolismo
2.
Biochim Biophys Acta Bioenerg ; 1863(1): 148507, 2022 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-34728155

RESUMO

Photosynthetic electron transfer comprises a series of light-induced redox reactions catalysed by multiprotein machinery in the thylakoid. These protein complexes possess cofactors susceptible to redox modifications by reactive small molecules. The gaseous radical nitric oxide (NO), a key signalling molecule in green algae and plants, has earlier been shown to bind to Photosystem (PS) II and obstruct electron transfer in plants. The effects of NO on cyanobacterial bioenergetics however, have long remained obscure. In this study, we exposed the model cyanobacterium Synechocystis sp. PCC 6803 to NO under anoxic conditions and followed changes in whole-cell fluorescence and oxidoreduction of P700 in vivo. Our results demonstrate that NO blocks photosynthetic electron transfer in cells by repressing PSII, PSI, and likely the NDH dehydrogenase-like complex 1 (NDH-1). We propose that iron­sulfur clusters of NDH-1 complex may be affected by NO to such an extent that ferredoxin-derived electron injection to the plastoquinone pool, and thus cyclic electron transfer, may be inhibited. These findings reveal the profound effects of NO on Synechocystis cells and demonstrate the importance of controlled NO homeostasis in cyanobacteria.


Assuntos
Complexo de Proteína do Fotossistema II , Transporte de Elétrons , Synechocystis
3.
Bioorg Chem ; 118: 105477, 2022 01.
Artigo em Inglês | MEDLINE | ID: mdl-34814084

RESUMO

Cyanobacteria Synechocystis sp. PCC 6803 was exploited as green cell factory for light-powered asymmetric synthesis of aromatic chiral alcohols. The effect of temperature, light, substrate and cell concentration on substrate conversions were investigated. Under the optimal condition, a series of chiral alcohols were synthesized with conversions up to 95% and enantiomer excess (ee) > 99%. We found that the addition of Na2S2O3 and Angeli's Salt increased the NADPH content by 20% and 25%, respectively. As a result, the time to reach 95% substrate conversion was shortened by 12 h, which demonstrated that the NADPH regeneration and hence the reaction rates can be regulated in cyanobacteria. This blue-green algae based biocatalysis showed its potential for chiral compounds production in future.


Assuntos
Álcoois/metabolismo , Luz , NADP/biossíntese , Synechocystis/química , Álcoois/química , Estrutura Molecular , NADP/química , Synechocystis/metabolismo
4.
Biol Direct ; 16(1): 26, 2021 12 14.
Artigo em Inglês | MEDLINE | ID: mdl-34906211

RESUMO

Microorganisms evolved specific acclimation strategies to thrive in environments of high or fluctuating salinities. Here, salt acclimation in the model cyanobacterium Synechocystis sp. PCC 6803 was analyzed by integrating transcriptomic, proteomic and metabolomic data. A dynamic reorganization of the transcriptome occurred during the first hours after salt shock, e.g. involving the upregulation of genes to activate compatible solute biochemistry balancing osmotic pressure. The massive accumulation of glucosylglycerol then had a measurable impact on the overall carbon and nitrogen metabolism. In addition, we observed the coordinated induction of putative regulatory RNAs and of several proteins known for their involvement in other stress responses. Overall, salt-induced changes in the proteome and transcriptome showed good correlations, especially among the stably up-regulated proteins and their transcripts. We define an extended salt stimulon comprising proteins directly or indirectly related to compatible solute metabolism, ion and water movements, and a distinct set of regulatory RNAs involved in post-transcriptional regulation. Our comprehensive data set provides the basis for engineering cyanobacterial salt tolerance and to further understand its regulation.


Assuntos
Proteômica , Synechocystis , Proteínas de Bactérias/genética , Pressão Osmótica , Estresse Salino
5.
Arch Microbiol ; 204(1): 66, 2021 Dec 23.
Artigo em Inglês | MEDLINE | ID: mdl-34940910

RESUMO

Synechocystis sp. PCC 6803 grown continuously in a 5-L photo-bioreactor for 20 months was found to have associated consortia with heterotrophic microorganisms. Two strains of bacteria were isolated from the long-term cultures of cyanobacteria with the aim to test whether their presence affects cyanobacterial growth and metabolism. The two strains were phylogenetically identified as Paenibacillus camelliae and Curtobacterium ammoniigenes, respectively. Co-culturing the Synechocystis sp. with either of the isolates under photoautotrophic and photoheterotrophic conditions exerted a statistically significant growth enhancement effect on cyanobacteria. Under co-culture experiments, the addition of P. camelliae resulted in a four-fold higher biomass yield with a considerable decrease in the stationary period. The growth was more pronounced on the addition of acetate to the culture media. Growth-enhancing factors like indole acetic acid (IAA) and siderophores were detected in the co-culture conditions which proved to be the main driving force in boosting cyanobacterial growth. Thus, the cyanobacteria-bacteria consortia can be very useful for augmenting biomass production by circumventing the time factor which can be further exploited for various biotechnological applications.


Assuntos
Paenibacillus , Synechocystis , Actinobacteria , Biomassa
6.
Biochemistry ; 60(51): 3841-3855, 2021 12 28.
Artigo em Inglês | MEDLINE | ID: mdl-34898175

RESUMO

The O2-evolving Mn4Ca cluster in photosystem II (PSII) is arranged as a distorted Mn3Ca cube that is linked to a fourth Mn ion (denoted as Mn4) by two oxo bridges. The Mn4 and Ca ions are bridged by residue D1-D170. This is also the only residue known to participate in the high-affinity Mn(II) site that participates in the light-driven assembly of the Mn4Ca cluster. In this study, we use Fourier transform infrared difference spectroscopy to characterize the impact of the D1-D170E mutation. On the basis of analyses of carboxylate and carbonyl stretching modes and the O-H stretching modes of hydrogen-bonded water molecules, we show that this mutation alters the extensive network of hydrogen bonds that surrounds the Mn4Ca cluster in the same manner as that of many other mutations. It also alters the equilibrium between conformers of the Mn4Ca cluster in the dark-stable S1 state so that a high-spin form of the S2 state is produced during the S1-to-S2 transition instead of the low-spin form that gives rise to the S2 state multiline electron paramagnetic resonance signal. The mutation may also change the coordination mode of the carboxylate group at position 170 to unidentate ligation of Mn4. This is the first mutation of a metal ligand in PSII that substantially impacts the spectroscopic signatures of the Mn4Ca cluster without substantially eliminating O2 evolution. The results have significant implications for our understanding of the roles of alternate active/inactive conformers of the Mn4Ca cluster in the mechanism of O2 formation.


Assuntos
Complexo de Proteína do Fotossistema II/química , Complexo de Proteína do Fotossistema II/genética , Substituição de Aminoácidos , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Cálcio/química , Ácidos Carboxílicos/química , Ligação de Hidrogênio , Ligantes , Compostos de Manganês/química , Modelos Moleculares , Mutagênese Sítio-Dirigida , Oxirredução , Complexo de Proteína do Fotossistema II/metabolismo , Conformação Proteica , Espectroscopia de Infravermelho com Transformada de Fourier , Synechocystis/química , Synechocystis/genética , Synechocystis/metabolismo
7.
PLoS One ; 16(12): e0261135, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34914753

RESUMO

The detection and identification of heavy metal contaminants are becoming increasingly important as environmental pollution causes an ever-increasing health hazard in the last decades. Bacterial heavy metal reporters, which constitute an environmentally friendly and cheap approach, offer great help in this process. Although their application has great potential in the detection of heavy metal contamination, their sensitivity still needs to be improved. In this study, we describe a simple molecular biology approach to improve the sensitivity of bacterial heavy metal biosensors. The constructs are luxAB marker genes regulated by the promoters of heavy metal exporter genes. We constructed a mutant strain lacking the cluster of genes responsible for heavy metal transport and hence achieved increased intracellular heavy metal content of the Synechocystis PCC6803 cyanobacterium. Taking advantage of this increased intracellular heavy metal concentration the Ni2+; Co2+ and Zn2+ detection limits of the constructs were three to tenfold decreased compared to the sensitivity of the same constructs in the wild-type cyanobacterium.


Assuntos
Proteínas de Bactérias/metabolismo , Técnicas Biossensoriais/métodos , Poluentes Ambientais/análise , Metais Pesados/análise , Regiões Promotoras Genéticas , Synechocystis/metabolismo , Proteínas de Bactérias/genética , Poluentes Ambientais/metabolismo , Engenharia Genética , Transporte de Íons , Limite de Detecção , Metais Pesados/metabolismo , Mutação , Synechocystis/genética , Synechocystis/crescimento & desenvolvimento
8.
Metab Eng ; 68: 131-141, 2021 11.
Artigo em Inglês | MEDLINE | ID: mdl-34601120

RESUMO

Decoupling growth from product synthesis is a promising strategy to increase carbon partitioning and maximize productivity in cell factories. However, reduction in both substrate uptake rate and metabolic activity in the production phase are an underlying problem for upscaling. Here, we used CRISPR interference to repress growth in lactate-producing Synechocystis sp. PCC 6803. Carbon partitioning to lactate in the production phase exceeded 90%, but CO2 uptake was severely reduced compared to uptake during the growth phase. We characterized strains during the onset of growth arrest using transcriptomics and proteomics. Multiple genes involved in ATP homeostasis were regulated once growth was inhibited, which suggests an alteration of energy charge that may lead to reduced substrate uptake. In order to overcome the reduced metabolic activity and take advantage of increased carbon partitioning, we tested a novel production strategy that involved alternating growth arrest and recovery by periodic addition of an inducer molecule to activate CRISPRi. Using this strategy, we maintained lactate biosynthesis in Synechocystis for 30 days in a constant light turbidostat cultivation. Cumulative lactate titers were also increased by 100% compared to a constant growth-arrest regime, and reached 1 g/L. Further, the cultivation produced lactate for 30 days, compared to 20 days for the non-growth arrest cultivation. Periodic growth arrest could be applicable for other products, and in cyanobacteria, could be linked to internal circadian rhythms that persist in constant light.


Assuntos
Ácido Láctico , Synechocystis , Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas , Synechocystis/genética
9.
Appl Microbiol Biotechnol ; 105(21-22): 8377-8392, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34668984

RESUMO

The toxicity of methyl viologen (MV) to organisms is mainly due to the oxidative stress caused by reactive oxygen species produced from cell response. This study mainly investigated the response of Synechocystis sp. PCC 6803 to MV by combining transcriptomic and metabolomic analyses. Through transcriptome sequencing, we found many genes responding to MV stress, and analyzed them by weighted gene co-expression network analysis (WGCNA). Meanwhile, many metabolites were also found by metabolomic analysis to be regulated post MV treatment. Based on the analysis results of Kyoto encyclopedia of genes and genomes (KEGG) of the differentially expressed genes (DEGs) in the transcriptome and the differential metabolites in the metabolome, the dynamic changes of genes and metabolites involved in ten metabolic pathways in response to MV were analyzed. The results indicated that although the oxidative stress caused by MV was the strongest at 6 h, the proportion of the upregulated genes and metabolites involved in these ten metabolic pathways was the highest. Photosynthesis positively regulated the response to MV-induced oxidative stress, and the regulation of environmental information processing was inhibited by MV. Other metabolic pathways played different roles at different times and interacted with each other to respond to MV. This study comprehensively analyzed the response of Synechocystis sp. PCC 6803 to oxidative stress caused by MV from a multi-omics perspective, with providing key data and important information for in-depth analysis of the response of organisms to MV, especially photosynthetic organisms. KEY POINTS: • Methyl viologen (MV) treatment caused regulatory changes in genes and metabolites. • Proportion of upregulated genes and metabolites was the highest at 6-h MV treatment. • Photosynthesis and environmental information processing involved in MV response.


Assuntos
Synechocystis , Redes e Vias Metabólicas/genética , Metaboloma , Paraquat , Synechocystis/genética , Transcriptoma
10.
Int J Mol Sci ; 22(19)2021 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-34638772

RESUMO

Free fatty acids (FFAs) are generated by the reaction of lipases with membrane lipids. Generated polyunsaturated fatty acids (PUFAs) containing more than two double bonds have toxic effects in photosynthetic organisms. In the present study, we examined the effect of exogenous FFAs in the growth medium on the activity of photosystem II (PSII) under strong light in the cyanobacterium Synechocystis sp. PCC 6803 (Synechocystis). PUFAs but not monounsaturated fatty acids accelerated the rate of photodamage to PSII by inactivating electron transfer at the oxygen-evolving complex. Moreover, supplemented PUFAs were specifically incorporated into the sn-2 position of phosphatidylglycerol (PG), which usually contains C16 fatty acids at the sn-2 position in Synechocystis cells. The disruption of the gene for an acyl-ACP synthetase reduced the effect of PUFAs on the photoinhibition of PSII. Thus, the specific incorporation of PUFAs into PG molecules requires acyl-ACP synthetase and leads to an unstable PSII, thereby accelerating photodamage to PSII. Our results are a breakthrough into elucidating the molecular mechanism of the toxicity of PUFAs to photosynthetic organisms.


Assuntos
Ácidos Graxos Insaturados/metabolismo , Fosfatidilgliceróis/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Synechocystis/metabolismo
11.
Metab Eng ; 68: 199-209, 2021 11.
Artigo em Inglês | MEDLINE | ID: mdl-34673236

RESUMO

Molecular hydrogen (H2) is considered as an ideal energy carrier to replace fossil fuels in future. Biotechnological H2 production driven by oxygenic photosynthesis appears highly promising, as biocatalyst and H2 syntheses rely mainly on light, water, and CO2 and not on rare metals. This biological process requires coupling of the photosynthetic water oxidizing apparatus to a H2-producing hydrogenase. However, this strategy is impeded by the simultaneous release of oxygen (O2) which is a strong inhibitor of most hydrogenases. Here, we addressed this challenge, by the introduction of an O2-tolerant hydrogenase into phototrophic bacteria, namely the cyanobacterial model strain Synechocystis sp. PCC 6803. To this end, the gene cluster encoding the soluble, O2-tolerant, and NAD(H)-dependent hydrogenase from Ralstonia eutropha (ReSH) was functionally transferred to a Synechocystis strain featuring a knockout of the native O2 sensitive hydrogenase. Intriguingly, photosynthetically active cells produced the O2 tolerant ReSH, and activity was confirmed in vitro and in vivo. Further, ReSH enabled the constructed strain Syn_ReSH+ to utilize H2 as sole electron source to fix CO2. Syn_ReSH+ also was able to produce H2 under dark fermentative conditions as well as in presence of light, under conditions fostering intracellular NADH excess. These findings highlight a high level of interconnection between ReSH and cyanobacterial redox metabolism. This study lays a foundation for further engineering, e.g., of electron transfer to ReSH via NADPH or ferredoxin, to finally enable photosynthesis-driven H2 production.


Assuntos
Hidrogenase , Synechocystis , Hidrogênio , Hidrogenase/genética , Oxigênio , Fotossíntese , Synechocystis/genética , Synechocystis/metabolismo
12.
Environ Sci Technol ; 55(20): 13971-13979, 2021 10 19.
Artigo em Inglês | MEDLINE | ID: mdl-34591446

RESUMO

Understanding of mercury (Hg) complexation with low molecular weight (LMW) bioligands will help elucidate its speciation. In natural waters, the rate of this complexation is governed by physicochemical, geochemical, and biochemical parameters. However, the role of bioligands involved in Hg intracellular handling by aquatic microorganisms is not well documented. Here, we combine the use of isotopically labeled Hg species (inorganic and monomethylmercury, iHg and MeHg) with gas or liquid chromatography coupling to elemental and molecular mass spectrometry to explore the role of intracellular biogenic ligands involved in iHg and MeHg speciation in cyanobacterium Synechocystis sp. PCC 6803, a representative phytoplankton species. This approach allowed to track resulting metabolic and newly found intracellular Hg biocomplexes (e.g., organic thiols) in Synechocystis sp. PCC 6803 finding different intracellular Hg species binding affinities with both high and low molecular weight (HMW and LMW) bioligands in the exponential and stationary phase. Furthermore, the parallel detection with both elemental and molecular ionization sources allowed the sensitive detection and molecular identification of glutathione (GSH) as the main low molecular weight binding ligand to iHg ((GS)2-Hg) and MeHg (GS-MeHg) in the cytosolic fraction. Such a novel experimental approach expands our knowledge on the role of biogenic ligands involved in iHg and MeHg intracellular handling in cyanobacteria.


Assuntos
Mercúrio , Compostos de Metilmercúrio , Synechocystis , Poluentes Químicos da Água , Mercúrio/análise , Fitoplâncton , Compostos de Sulfidrila , Poluentes Químicos da Água/análise
13.
J Biol Chem ; 297(4): 101186, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34517006

RESUMO

Reactive oxygen species are key factors that strongly affect the cellular redox state and regulate various physiological and cellular phenomena. To monitor changes in the redox state, we previously developed fluorescent redox sensors named Re-Q, the emissions of which are quenched under reduced conditions. However, such fluorescent probes are unsuitable for use in the cells of photosynthetic organisms because they require photoexcitation that may change intracellular conditions and induce autofluorescence, primarily in chlorophylls. In addition, the presence of various chromophore pigments may interfere with fluorescence-based measurements because of their strong absorbance. To overcome these problems, we adopted the bioluminescence resonance energy transfer (BRET) mechanism for the sensor and developed two BRET-based redox sensors by fusing cyan fluorescent protein-based or yellow fluorescent protein-based Re-Q with the luminescent protein Nluc. We named the resulting redox-sensitive BRET-based indicator probes "ROBINc" and "ROBINy." ROBINc is pH insensitive, which is especially vital for observation in photosynthetic organisms. By using these sensors, we successfully observed dynamic redox changes caused by an anticancer agent in HeLa cells and light/dark-dependent redox changes in the cells of photosynthetic cyanobacterium Synechocystis sp. PCC 6803. Since the newly developed sensors do not require excitation light, they should be especially useful for visualizing intracellular phenomena caused by redox changes in cells containing colored pigments.


Assuntos
Transferência Ressonante de Energia de Fluorescência , Proteínas de Fluorescência Verde , Synechocystis , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Células HeLa , Humanos , Oxirredução , Synechocystis/genética , Synechocystis/metabolismo
14.
Nat Commun ; 12(1): 5387, 2021 09 10.
Artigo em Inglês | MEDLINE | ID: mdl-34508071

RESUMO

Photosynthesis and respiration rely upon a proton gradient to produce ATP. In photosynthesis, the Respiratory Complex I homologue, Photosynthetic Complex I (PS-CI) is proposed to couple ferredoxin oxidation and plastoquinone reduction to proton pumping across thylakoid membranes. However, little is known about the PS-CI molecular mechanism and attempts to understand its function have previously been frustrated by its large size and high lability. Here, we overcome these challenges by pushing the limits in sample size and spectroscopic sensitivity, to determine arguably the most important property of any electron transport enzyme - the reduction potentials of its cofactors, in this case the iron-sulphur clusters of PS-CI (N0, N1 and N2), and unambiguously assign them to the structure using double electron-electron resonance. We have thus determined the bioenergetics of the electron transfer relay and provide insight into the mechanism of PS-CI, laying the foundations for understanding of how this important bioenergetic complex functions.


Assuntos
Proteínas de Bactérias/metabolismo , Metabolismo Energético , Proteínas Ferro-Enxofre/metabolismo , Complexo de Proteína do Fotossistema I/metabolismo , Proteínas de Bactérias/isolamento & purificação , Proteínas de Bactérias/ultraestrutura , Espectroscopia de Ressonância de Spin Eletrônica , Transporte de Elétrons , Proteínas Ferro-Enxofre/ultraestrutura , Complexo de Proteína do Fotossistema I/isolamento & purificação , Complexo de Proteína do Fotossistema I/ultraestrutura , Synechocystis/metabolismo
15.
Photochem Photobiol Sci ; 20(9): 1209-1227, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34478050

RESUMO

Femtosecond absorption spectroscopy of Photosystem I (PS I) complexes from the cyanobacterium Synechocystis sp. PCC 6803 was carried out on three pairs of complementary amino acid substitutions located near the second pair of chlorophyll molecules Chl2A and Chl2B (also termed A-1A and A-1B). The absorption dynamics at delays of 0.1-500 ps were analyzed by decomposition into discrete decay-associated spectra and continuously distributed exponential components. The multi-exponential deconvolution of the absorption changes revealed that the electron transfer reactions in the PsaA-N600M, PsaA-N600H, and PsaA-N600L variants near the B-branch of cofactors are similar to those of the wild type, while the PsaB-N582M, PsaB-N582H, and PsaB-N582L variants near the A-branch of cofactors cause significant alterations of the photochemical processes, making them heterogeneous and poorly described by a discrete exponential kinetic model. A redistribution of the unpaired electron between the second and the third monomers Chl2A/Chl2B and Chl3A/Chl3B was identified in the time range of 9-20 ps, and the subsequent reduction of A1 was identified in the time range of 24-70 ps. In the PsaA-N600L and PsaB-N582H/L variants, the reduction of A1 occurred with a decreased quantum yield of charge separation. The decreased quantum yield correlates with a slowing of the phylloquinone A0 → A1 reduction, but not with the initial transient spectra measured at the shortest time delay. The results support a branch competition model, where the electron is sheared between Chl2A-Chl3A and Chl2B-Chl3B cofactors before its transfer to phylloquinone in either A1A or A1B sites.


Assuntos
Proteínas de Bactérias/química , Clorofila/química , Complexo de Proteína do Fotossistema I/química , Synechocystis/química , Transporte de Elétrons , Cinética , Modelos Moleculares
16.
J Biotechnol ; 340: 47-56, 2021 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-34481001

RESUMO

Low production rates are still one limiting factor for the industrial climate-neutral production of biovaluable compounds in cyanobacteria. Next to optimized cultivation conditions, new production strategies are required. Hence, the use of established molecular tools could lead to increased product yields in the cyanobacterial model organism Synechocystis sp. PCC6803. Its main storage compound glycogen was chosen to be increased by the use of these tools. In this study, the three genes glgC, glgA1 and glgA2, which are part of the glycogen synthesis pathway, were combined with the Pcpc560 promoter and the neutral cloning site NSC1. The complete genome integration, protein formation, biomass production and glycogen accumulation were determined to select the most productive transformants. The overexpression of glgA2 did not increase the biomass or glycogen production in short-term trials compared to the other two genes but caused transformants death in long-term trials. The transformants glgA1_11 and glgC_2 showed significantly increased biomass (1.6-fold - 1.7-fold) and glycogen production (3.5-fold - 4-fold) compared to the wild type after 96 h making them a promising energy source for further applications. Those could include for example a two-stage production process, with first energy production (glycogen) and second increased product formation (e.g. ethanol).


Assuntos
Synechocystis , Glicogênio , Synechocystis/genética
17.
Environ Int ; 157: 106842, 2021 12.
Artigo em Inglês | MEDLINE | ID: mdl-34438231

RESUMO

Although nanoplastics/microplastics (NPs/MPs) may interact with co-contaminants (e.g. antibiotics) in aquatic systems, little is known about their combined toxicity. Here, we compared the individual toxicity of NPs/MPs or ciprofloxacin (CIP, a very commonly detected antibiotic) and their combined toxicity toward a unicellular cyanobacterium Synechocystis sp. in terms of the cellular responses and metabolomic analysis. We found that CIP exhibited an antagonistic effect with NPs/MPs due to its adsorption onto the surface of NPs/MPs. Particle size-dependent toxic effects of NPs/MPs were observed. Reactive oxygen species (ROS) was verified as an important factor for NPs/MPs to inhibit cell growth, other than for CIP. Metabolomics further revealed that Synechocystis sp. up-regulated glycerophospholipids, amino acids, nucleotides, and carbohydrates to tolerate CIP pressure. NPs/MPs downregulated the TCA cycle and glycerophospholipids metabolism and impaired the primary production and membrane integrity via adhesion with Synechocystis sp.. Additionally, the toxicity of NPs/MPs throughout ten growth cycles at a sublethal concentration unveiled its potential risks in interfering with metabolism. Collectively, our findings provide insights into the joint ecotoxicity of NPs/MPs and antibiotics, and highlight the potential risks of co-pollutants at environmental relevant concentrations.


Assuntos
Synechocystis , Poluentes Químicos da Água , Ciprofloxacina/toxicidade , Microplásticos , Plásticos , Poluentes Químicos da Água/análise
18.
Elife ; 102021 08 26.
Artigo em Inglês | MEDLINE | ID: mdl-34435952

RESUMO

Photosynthetic organisms have adapted to survive a myriad of extreme environments from the earth's deserts to its poles, yet the proteins that carry out the light reactions of photosynthesis are highly conserved from the cyanobacteria to modern day crops. To investigate adaptations of the photosynthetic machinery in cyanobacteria to excessive light stress, we isolated a new strain of cyanobacteria, Cyanobacterium aponinum 0216, from the extreme light environment of the Sonoran Desert. Here we report the biochemical characterization and the 2.7 Å resolution structure of trimeric photosystem I from this high-light-tolerant cyanobacterium. The structure shows a new conformation of the PsaL C-terminus that supports trimer formation of cyanobacterial photosystem I. The spectroscopic analysis of this photosystem I revealed a decrease in far-red absorption, which is attributed to a decrease in the number of long- wavelength chlorophylls. Using these findings, we constructed two chimeric PSIs in Synechocystis sp. PCC 6803 demonstrating how unique structural features in photosynthetic complexes can change spectroscopic properties, allowing organisms to thrive under different environmental stresses.


Assuntos
Cianobactérias/genética , Cianobactérias/fisiologia , Complexo de Proteína do Fotossistema I/química , Complexo de Proteína do Fotossistema I/genética , Aclimatação , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Clorofila , Microscopia Crioeletrônica , Luz , Modelos Moleculares , Fotossíntese , Complexo de Proteína do Fotossistema I/metabolismo , Conformação Proteica , Synechocystis/metabolismo
19.
Sci Total Environ ; 800: 149561, 2021 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-34426369

RESUMO

Cyanobacteria can grow using inorganic substrates, such as CO2 from industrial sources and nutrients from wastewaters, and therefore are promising microorganisms to produce polyhydroxybutyrate in a cleaner circular context. However, this biotechnological production is highly challenging because it involves different interlinked reactions that are affected by environmental conditions, which hinders process optimization. In this study a new biokinetic mechanistic model using novel experimental approaches was developed to optimize polyhydroxybutyrate (PHB) and glycogen production. The model includes, for the first time, the production of glycogen and its conversion into PHB, which has been found as the main pathway to produce PHB. Model was successfully (r2: 0.6-0.99) calibrated and validated with experimental data from photobioreactors inoculated with Synechocystis sp. The developed model was used to determine suitable initial conditions for a lab scale batch reactor (6.4 mgN·L-1 and 2 mgP·L-1) and a new configuration for the continuous industrial production of PHB was proposed and optimized using this tool. The maximum productivity (5.1 mgPHB·L-1·d-1) and the optimal configuration and operation of the serial reactors to produce PHB in an industrial scale was achieved using a hydraulic retention time of 4 days in the growth reactor. Then, this reactor daily fed 20 batch accumulation reactors, which were discharged after 20 days. The optimal influent nutrients concentrations for this configuration was found to be 50 mgN·L-1 and 10 mgP·L-1. Results found in this study show the necessity to optimize biopolymers production with Cyanobacteria considering environmental conditions, and demonstrated the potential of this model as a tool to increase PHB productivity.


Assuntos
Synechocystis , Biopolímeros , Glicogênio , Cinética , Fotobiorreatores , Poliésteres
20.
Sci Rep ; 11(1): 17131, 2021 08 24.
Artigo em Inglês | MEDLINE | ID: mdl-34429477

RESUMO

A unicellular cyanobacterium Synechocystis sp. PCC 6803 possesses a unique tricarboxylic acid (TCA) cycle, wherein the intracellular citrate levels are approximately 1.5-10 times higher than the levels of other TCA cycle metabolite. Aconitase catalyses the reversible isomerisation of citrate and isocitrate. Herein, we biochemically analysed Synechocystis sp. PCC 6803 aconitase (SyAcnB), using citrate and isocitrate as the substrates. We observed that the activity of SyAcnB for citrate was highest at pH 7.7 and 45 °C and for isocitrate at pH 8.0 and 53 °C. The Km value of SyAcnB for citrate was higher than that for isocitrate under the same conditions. The Km value of SyAcnB for isocitrate was 3.6-fold higher than the reported Km values of isocitrate dehydrogenase for isocitrate. Therefore, we suggest that citrate accumulation depends on the enzyme kinetics of SyAcnB, and 2-oxoglutarate production depends on the chemical equilibrium in this cyanobacterium.


Assuntos
Aconitato Hidratase/metabolismo , Proteínas de Bactérias/metabolismo , Ácido Cítrico/metabolismo , Synechocystis/enzimologia , Ácido Cítrico/análogos & derivados , Concentração de Íons de Hidrogênio , Isomerismo , Cinética , Especificidade por Substrato , Synechocystis/metabolismo , Temperatura
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