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1.
J Biotechnol ; 297: 41-48, 2019 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-30898687

RESUMO

Scaling of phototrophic bioprocesses can be extremely challenging especially when reactor types in the considered scales differ. In this study, the mean integral photon flux density was used to transfer light-dependent growth kinetics of Nannochloropsis salina 40.85 and Nannochloropsis gaditana 2.99 grown with constant LED irradiation from flat-plate gas-lift photobioreactors (0.09 m2) to thin-layer cascade photobioreactors (8 m2). Even though completely different reactors were used, comparable growth rates were achieved on both scales with both strains by application of comparable mean light availabilities in the microalgae suspensions. In contrast, the light-dependent growth kinetics change significantly when irradiation varies dynamically (day-night cycles). The maximum intra-day growth rate of N. salina with dynamic climate simulation was doubled to 0.07 h-1 compared to constant irradiation, but tolerance of the microalgae against excessive irradiation was drastically reduced compared to constant irradiation. Because of that, predicting growth of N. salina in a physically simulated day-night climate would require the determination of the light-dependence of growth with dynamically varying conditions.


Assuntos
Luz , Microalgas/crescimento & desenvolvimento , Microalgas/efeitos da radiação , Fotobiorreatores/microbiologia , Processos Fototróficos/efeitos da radiação , Técnicas de Cultura Celular por Lotes , Biomassa , Cinética , Região do Mediterrâneo , Estações do Ano
2.
Nat Commun ; 9(1): 2530, 2018 06 28.
Artigo em Inglês | MEDLINE | ID: mdl-29955055

RESUMO

While significant efforts have been invested in reconstructing the early evolution of the Earth's atmosphere-ocean-biosphere biogeochemical nitrogen cycle, the potential role of an early continental contribution by a terrestrial, microbial phototrophic biosphere has been largely overlooked. By transposing to the Archean nitrogen fluxes of modern topsoil communities known as biological soil crusts (terrestrial analogs of microbial mats), whose ancestors might have existed as far back as 3.2 Ga ago, we show that they could have impacted the evolution of the nitrogen cycle early on. We calculate that the net output of inorganic nitrogen reaching the Precambrian hydrogeological system could have been of the same order of magnitude as that of modern continents for a range of inhabited area as small as a few percent of that of present day continents. This contradicts the assumption that before the Great Oxidation Event, marine and continental biogeochemical nitrogen cycles were disconnected.


Assuntos
Consórcios Microbianos/fisiologia , Ciclo do Nitrogênio/fisiologia , Nitrogênio/química , Processos Fototróficos/fisiologia , Ecossistema , História Antiga , Consórcios Microbianos/efeitos da radiação , Nitrogênio/história , Nitrogênio/metabolismo , Isótopos de Nitrogênio , Oceanos e Mares , Origem da Vida , Oxirredução , Oxigênio/química , Oxigênio/história , Oxigênio/metabolismo , Processos Fototróficos/efeitos da radiação , Solo/química , Luz Solar
3.
Mol Ecol ; 27(14): 2913-2925, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29679511

RESUMO

Phototrophic biofilms are ubiquitous in freshwater and marine environments where they are critical for biogeochemical cycling, food webs and in industrial applications. In streams, phototrophic biofilms dominate benthic microbial life and harbour an immense prokaryotic and eukaryotic microbial biodiversity with biotic interactions across domains and trophic levels. Here, we examine how community structure and function of these biofilms respond to varying light availability, as the crucial energy source for phototrophic biofilms. Using metatranscriptomics, we found that under light limitation-dominant phototrophs, including diatoms and cyanobacteria, displayed a remarkable plasticity in their photosynthetic machinery manifested as higher abundance of messenger RNAs (mRNAs) involved in photosynthesis and chloroplast ribosomal RNA. Under higher light availability, bacterial mRNAs involved in phosphorus metabolism, mainly from Betaproteobacteria and Cyanobacteria, increased, likely compensating for nutrient depletion in thick biofilms with high biomass. Consumers, including diverse ciliates, displayed community shifts indicating preferential grazing on algae instead of bacteria under higher light. For the first time, we show that the functional integrity of stream biofilms under variable light availability is maintained by structure-function adaptations on several trophic levels. Our findings shed new light on complex biofilms, or "microbial jungles", where in analogy to forests, diverse and multitrophic level communities lend stability to ecosystem functioning. This multitrophic level perspective, coupling metatranscriptomics to process measurements, could advance understanding of microbial-driven ecosystems beyond biofilms, including planktonic and soil environments.


Assuntos
Biofilmes/crescimento & desenvolvimento , Cianobactérias/crescimento & desenvolvimento , Ecossistema , Fotossíntese/genética , Biodiversidade , Biofilmes/efeitos da radiação , Biomassa , Cianobactérias/genética , Cianobactérias/efeitos da radiação , Água Doce , Fósforo/metabolismo , Processos Fototróficos/efeitos da radiação , RNA Mensageiro/genética , Rios
4.
Plant Cell Physiol ; 58(10): 1622-1630, 2017 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-29016945

RESUMO

Plants have mechanisms allowing them to acclimate to intense light conditions, which involves the dissipation of excess light energy. These mechanisms allow plants to perform photosynthesis efficiently and, therefore, must be accurately and precisely controlled. However, how plants dissipate excess light energy has yet to be fully elucidated. Herein we report the identification of a gene, which we named Fluctuating-Light-Acclimation Protein1 (FLAP1), that is conserved in oxygenic phototrophs. We show that Arabidopsis FLAP1 is associated with chloroplast thylakoid and envelope membranes and that the flap1 mutant shows delayed non-photochemical quenching (NPQ) relaxation during induction of photosynthesis at moderate light intensity. Under fluctuating light conditions, NPQ levels in the flap1 mutant were higher than those in the wild type during the high light period, and the mutant exhibited a pale-green phenotype. These findings suggest that FLAP1 is involved in NPQ control, which is important for an acclimation response to fluctuating light.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/fisiologia , Cloroplastos/metabolismo , Homeostase , Oxigênio/metabolismo , Processos Fotoquímicos , Processos Fototróficos , Prótons , Aclimatação , Arabidopsis/genética , Arabidopsis/efeitos da radiação , Arabidopsis/ultraestrutura , Cloroplastos/efeitos da radiação , Cloroplastos/ultraestrutura , Genes de Plantas , Estudos de Associação Genética , Membranas Intracelulares/metabolismo , Cinética , Luz , Mutação/genética , Fenótipo , Processos Fotoquímicos/efeitos da radiação , Fotossíntese/efeitos da radiação , Processos Fototróficos/efeitos da radiação
5.
Autophagy ; 13(8): 1318-1330, 2017 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-28594263

RESUMO

Magnaporthe oryzae, the ascomycete fungus that causes rice blast disease, initiates conidiation in response to light when grown on Prune-Agar medium containing both carbon and nitrogen sources. Macroautophagy/autophagy was shown to be essential for M. oryzae conidiation and induced specifically upon exposure to light but is undetectable in the dark. Therefore, it is inferred that autophagy is naturally induced by light, rather than by starvation during M. oryzae conidiation. However, the signaling pathway(s) involved in such phototropic induction of autophagy remains unknown. We identified an M. oryzae ortholog of GCN5 (MGG_03677), encoding a histone acetyltransferase (HAT) that negatively regulates light- and nitrogen-starvation-induced autophagy, by acetylating the autophagy protein Atg7. Furthermore, we unveiled novel regulatory mechanisms on Gcn5 at both transcriptional and post-translational levels, governing its function associated with the unique phototropic response of autophagy in this pathogenic fungus. Thus, our study depicts a signaling network and regulatory mechanism underlying the autophagy induction by important environmental clues such as light and nutrients.


Assuntos
Autofagia , Biocatálise , Proteínas Fúngicas/metabolismo , Magnaporthe/citologia , Magnaporthe/metabolismo , Processos Fototróficos , Acetilação , Autofagia/efeitos da radiação , Regulação Fúngica da Expressão Gênica/efeitos da radiação , Genes Fúngicos , Luz , Magnaporthe/genética , Magnaporthe/efeitos da radiação , Processos Fototróficos/efeitos da radiação , Ligação Proteica , Processamento de Proteína Pós-Traducional/efeitos da radiação , Esporos Fúngicos/metabolismo , Esporos Fúngicos/efeitos da radiação , Transcrição Genética/efeitos da radiação
6.
Physiol Plant ; 161(1): 75-87, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28326554

RESUMO

High light causes photosystem II to generate singlet oxygen (1 O2 ), a reactive oxygen species (ROS) that can react with membrane lipids, releasing reactive electrophile species (RES), such as acrolein. To investigate how RES may contribute to light stress responses, Chlamydomonas reinhardtii was high light-treated in photoautotrophic and mixotrophic conditions and also in an oxygen-enriched atmosphere to elevate ROS production. The responses were compared to exogenous acrolein. Non-photochemical quenching (NPQ) was higher in photoautotrophic cells, as a consequence of a more de-epoxidized state of the xanthophyll cycle pool and more LHCSR3 protein, showing that photosynthesis was under more pressure than in mixotrophic cells. Photoautotrophic cells had lowered α-tocopherol and ß-carotene contents and a higher level of protein carbonylation, indicators of elevated 1 O2 production. Levels of glutathione, glutathione peroxidase (GPX5) and glutathione-S-transferase (GST1), important antioxidants against RES, were also increased in photoautotrophic cells. In parallel to the wild-type, the LHCSR3-deficient npq4 mutant was high light-treated, which in photoautotrophic conditions exhibited particular sensitivity under elevated oxygen, the treatment that induced the highest RES levels, including acrolein. The npq4 mutant had more GPX5 and GST1 alongside higher levels of carbonylated protein and a more oxidized glutathione redox state. In wild-type cells glutathione contents doubled after 4 h treatment, either with high light under elevated oxygen or with a non-critical dose (600 ppm) of acrolein. Exogenous acrolein also increased GST1 levels, but not GPX5. Overall, RES-associated oxidative damage and glutathione metabolism are prominently associated with light stress and potentially in signaling responses of C. reinhardtii.


Assuntos
Acroleína/metabolismo , Chlamydomonas reinhardtii/fisiologia , Chlamydomonas reinhardtii/efeitos da radiação , Luz , Processos Autotróficos/efeitos da radiação , Chlamydomonas reinhardtii/crescimento & desenvolvimento , Glutationa/metabolismo , Processos Fototróficos/efeitos da radiação , Pigmentos Biológicos/metabolismo , Proteínas de Plantas/metabolismo , Carbonilação Proteica
7.
Biochim Biophys Acta ; 1857(12): 1900-1908, 2016 12.
Artigo em Inglês | MEDLINE | ID: mdl-27659506

RESUMO

Actinorhodopsin (ActR) is a light-driven outward H+ pump. Although the genes of ActRs are widely spread among freshwater bacterioplankton, there are no prior data on their functional expression in native cell membranes. Here, we demonstrate ActR phototrophy in the native actinobacterium. Genome analysis showed that Candidatus Rhodoluna planktonica, a freshwater actinobacterium, encodes one microbial rhodopsin (RpActR) belonging to the ActR family. Reflecting the functional expression of RpActR, illumination induced the acidification of the actinobacterial cell suspension and then elevated the ATP content inside the cells. The photochemistry of RpActR was also examined using heterologously expressed RpActR in Escherichia coli membranes. The purified RpActR showed λmax at 534nm and underwent a photocycle characterized by the very fast formation of M intermediate. The subsequent intermediate, named P620, could be assigned to the O intermediate in other H+ pumps. In contrast to conventional O, the accumulation of P620 remains prominent, even at high pH. Flash-induced absorbance changes suggested that there exists only one kind of photocycle at any pH. However, above pH7, RpActR shows heterogeneity in the H+ transfer sequences: one first captures H+ and then releases it during the formation and decay of P620, while the other first releases H+ prior to H+ uptake during P620 formation.


Assuntos
Actinobacteria/efeitos da radiação , Trifosfato de Adenosina/metabolismo , Metabolismo Energético/efeitos da radiação , Luz , Processos Fototróficos/efeitos da radiação , Rodopsinas Microbianas/efeitos da radiação , Actinobacteria/genética , Actinobacteria/metabolismo , Transferência de Energia , Escherichia coli/genética , Escherichia coli/metabolismo , Genoma Bacteriano , Concentração de Íons de Hidrogênio , Cinética , Fotólise , Conformação Proteica , Prótons , Rodopsinas Microbianas/química , Rodopsinas Microbianas/genética , Rodopsinas Microbianas/metabolismo , Análise Espectral , Relação Estrutura-Atividade
8.
Plant Cell Physiol ; 57(10): 2091-2103, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27440548

RESUMO

Carbohydrate metabolism is a tightly regulated process in photosynthetic organisms. In the cyanobacterium Synechocystis sp. PCC 6803, the photomixotrophic growth protein A (PmgA) is involved in the regulation of glucose and storage carbohydrate (i.e. glycogen) metabolism, while its biochemical activity and possible factors acting downstream of PmgA are unknown. Here, a genome-wide microarray analysis of a ΔpmgA strain identified the expression of 36 protein-coding genes and 42 non-coding transcripts as significantly altered. From these, the non-coding RNA Ncr0700 was identified as the transcript most strongly reduced in abundance. Ncr0700 is widely conserved among cyanobacteria. In Synechocystis its expression is inversely correlated with light intensity. Similarly to a ΔpmgA mutant, a Δncr0700 deletion strain showed an approximately 2-fold increase in glycogen content under photoautotrophic conditions and wild-type-like growth. Moreover, its growth was arrested by 38 h after a shift to photomixotrophic conditions. Ectopic expression of Ncr0700 in Δncr0700 and ΔpmgA restored the glycogen content and photomixotrophic growth to wild-type levels. These results indicate that Ncr0700 is required for photomixotrophic growth and the regulation of glycogen accumulation, and acts downstream of PmgA. Hence Ncr0700 is renamed here as PmgR1 for photomixotrophic growth RNA 1.


Assuntos
Glicogênio/metabolismo , Processos Fototróficos/genética , RNA não Traduzido/metabolismo , Synechocystis/crescimento & desenvolvimento , Synechocystis/genética , Sequência de Bases , Regulação para Baixo/genética , Perfilação da Expressão Gênica , Regulação Bacteriana da Expressão Gênica/efeitos da radiação , Genoma Bacteriano , Genótipo , Luz , Mutação/genética , Processos Fototróficos/efeitos da radiação , RNA não Traduzido/genética , Reprodutibilidade dos Testes , Alinhamento de Sequência , Synechocystis/efeitos da radiação , Transcrição Genética/efeitos da radiação , Regulação para Cima/genética
9.
Plant Physiol ; 170(4): 1975-88, 2016 04.
Artigo em Inglês | MEDLINE | ID: mdl-26858365

RESUMO

When photosynthetic organisms are deprived of nitrogen (N), the capacity to grow and assimilate carbon becomes limited, causing a decrease in the productive use of absorbed light energy and likely a rise in the cellular reduction state. Although there is a scarcity of N in many terrestrial and aquatic environments, a mechanistic understanding of how photosynthesis adjusts to low-N conditions and the enzymes/activities integral to these adjustments have not been described. In this work, we use biochemical and biophysical analyses of photoautotrophically grown wild-type and mutant strains of Chlamydomonas reinhardtii to determine the integration of electron transport pathways critical for maintaining active photosynthetic complexes even after exposure of cells to N deprivation for 3 d. Key to acclimation is the type II NADPH dehydrogenase, NDA2, which drives cyclic electron flow (CEF), chlororespiration, and the generation of an H(+) gradient across the thylakoid membranes. N deprivation elicited a doubling of the rate of NDA2-dependent CEF, with little contribution from PGR5/PGRL1-dependent CEF The H(+) gradient generated by CEF is essential to sustain nonphotochemical quenching, while an increase in the level of reduced plastoquinone would promote a state transition; both are necessary to down-regulate photosystem II activity. Moreover, stimulation of NDA2-dependent chlororespiration affords additional relief from the elevated reduction state associated with N deprivation through plastid terminal oxidase-dependent water synthesis. Overall, rerouting electrons through the NDA2 catalytic hub in response to photoautotrophic N deprivation sustains cell viability while promoting the dissipation of excess excitation energy through quenching and chlororespiratory processes.


Assuntos
Aclimatação/efeitos dos fármacos , Chlamydomonas reinhardtii/fisiologia , Cloroplastos/metabolismo , NADPH Desidrogenase/metabolismo , Nitrogênio/farmacologia , Processos Fotoquímicos , Processos Autotróficos/efeitos dos fármacos , Processos Autotróficos/efeitos da radiação , Respiração Celular/efeitos dos fármacos , Chlamydomonas reinhardtii/efeitos dos fármacos , Cloroplastos/efeitos dos fármacos , Transporte de Elétrons/efeitos dos fármacos , Transporte de Elétrons/efeitos da radiação , Luz , Modelos Biológicos , NADP/metabolismo , Peptídeos/metabolismo , Processos Fotoquímicos/efeitos dos fármacos , Processos Fotoquímicos/efeitos da radiação , Fotossíntese/efeitos dos fármacos , Fotossíntese/efeitos da radiação , Complexo de Proteína do Fotossistema II/metabolismo , Processos Fototróficos/efeitos dos fármacos , Processos Fototróficos/efeitos da radiação , Pigmentação/efeitos dos fármacos , Pigmentação/efeitos da radiação , Pigmentos Biológicos/metabolismo , Plastoquinona/metabolismo , Subunidades Proteicas/metabolismo , Prótons
10.
Gig Sanit ; 95(10): 909-13, 2016.
Artigo em Russo | MEDLINE | ID: mdl-29431330

RESUMO

The article considers the problems offloodlights pollution in the territory of Crimea due to the work of illumination led equipment of the key elements of the international transport artery "China-Europe". There was performed a qualitative assessment of characteristics of led floodlights pollution on the example of the sea surface of the transport crossing through the Kerch Strait. Ichthyologists and oceanographers were shown to estimate the amount of phytoplankton biomass based on sunlight illumination. The excess dose of blue light in the spectrum of led lighting was established to have an impact on phytoplankton greater than solar and lunar light, creating preconditions for the increase of biological mass of phytoplankton and consequently to the formation of the "stern stock". Arising from additional phytoplankton biomass can significantly influence on the schedule offish migration in waters of the Kerch Strait, the biomass of mosquitoes and midges, which are prey for amphibians and birds. The decline of the both light pollution and its negative impact on fauna andflora requires the development of semiconductor sources of white light with a biologically adequate spectrum in the framework of the "Lighting of the lighting equipment of Crimea".


Assuntos
Organismos Aquáticos , Poluição Ambiental , Luz/efeitos adversos , Iluminação , Processos Fototróficos/efeitos da radiação , Urbanização , Organismos Aquáticos/fisiologia , Organismos Aquáticos/efeitos da radiação , Poluição Ambiental/efeitos adversos , Poluição Ambiental/análise , Poluição Ambiental/prevenção & controle , Humanos , Iluminação/efeitos adversos , Iluminação/métodos , Iluminação/normas , Fotometria/métodos , Fotometria/normas , Fitoplâncton/fisiologia , Fitoplâncton/efeitos da radiação , Saúde Pública/métodos , Saúde Pública/normas , Federação Russa/epidemiologia , Mudança Social
11.
Photosynth Res ; 127(3): 347-54, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26407568

RESUMO

This work studies how extracellular electron transfer (EET) from cyanobacteria-dominated marine microbial biofilms to solid electrodes is affected by the availability of inorganic carbon (Ci). The EET was recorded chronoamperometrically in the form of electrical current by a potentiostat in two identical photo-electrochemical cells using carbon electrodes poised at a potential of +0.6 V versus standard hydrogen electrode under 12/12 h illumination/dark cycles. The Ci was supplied by the addition of NaHCO3 to the medium and/or by sparging CO2 gas. At high Ci conditions, EET from the microbial biofilm to the electrodes was observed only during the dark phase, indicating the occurrence of a form of night-time respiration that can use insoluble electrodes as the terminal electron acceptor. At low or no Ci conditions, however, EET also occurred during illumination suggesting that, in the absence of their natural electron acceptor, some cyanobacteria are able to utilise solid electrodes as an electron sink. This may be a natural survival mechanism for cyanobacteria to maintain redox balance in environments with limiting CO2 and/or high light intensity.


Assuntos
Organismos Aquáticos/fisiologia , Organismos Aquáticos/efeitos da radiação , Elétrons , Consórcios Microbianos , Processos Fototróficos , Estresse Fisiológico/efeitos da radiação , Carbono/metabolismo , Respiração Celular , DNA Ribossômico/genética , Eletricidade , Eletrodos , Luz , Consórcios Microbianos/efeitos da radiação , Compostos Orgânicos/metabolismo , Oxirredução , Oxigênio/metabolismo , Processos Fototróficos/efeitos da radiação , Análise de Sequência de DNA
12.
PLoS One ; 10(9): e0139061, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26394153

RESUMO

The societal importance of renewable carbon-based commodities and energy carriers has elicited a particular interest for high performance phototrophic microorganisms. Selection of optimal strains is often based on direct comparison under laboratory conditions of maximal growth rate or additional valued features such as lipid content. Instead of reporting growth rate in culture, estimation of photosynthetic efficiency (quantum yield of PSII) by pulse-amplitude modulated (PAM) fluorimetry is an often applied alternative method. Here we compared the quantum yield of PSII and the photonic yield on biomass for the green alga Chlorella sorokiniana 211-8K and the cyanobacterium Synechocystis sp. PCC 6803. Our data demonstrate that the PAM technique inherently underestimates the photosynthetic efficiency of cyanobacteria by rendering a high F0 and a low FM, specifically after the commonly practiced dark pre-incubation before a yield measurement. Yet when comparing the calculated biomass yield on light in continuous culture experiments, we obtained nearly equal values for both species. Using mutants of Synechocystis sp. PCC 6803, we analyzed the factors that compromise its PAM-based quantum yield measurements. We will discuss the role of dark respiratory activity, fluorescence emission from the phycobilisomes, and the Mehler-like reaction. Based on the above observations we recommend that PAM measurements in cyanobacteria are interpreted only qualitatively.


Assuntos
Chlorella/fisiologia , Fluorometria/métodos , Fotossíntese , Synechocystis/fisiologia , Biomassa , Chlorella/efeitos da radiação , Clorofila/metabolismo , Clorofila A , Transporte de Elétrons/efeitos da radiação , Fluorescência , Luz , Espectrometria de Massas , Oxirredução/efeitos da radiação , Consumo de Oxigênio/efeitos da radiação , Fótons , Processos Fototróficos/efeitos da radiação , Ficobilissomas/metabolismo , Synechocystis/efeitos da radiação
14.
Bioresour Technol ; 184: 53-62, 2015 May.
Artigo em Inglês | MEDLINE | ID: mdl-25266686

RESUMO

The growth and oil production of nine Chlorella strains were comparatively assessed and Chlorellaprotothecoides CS-41 demonstrated the greatest lipid production potential. The effects of different nitrogen forms and concentrations, phosphorus concentrations and light intensities on growth and oil production were studied in laboratory columns. C. protothecoides CS-41 accumulated lipids up to 55% of dry weight, with triacylglycerol and oleic acid being 71% of total lipids and 59% of total fatty acids, respectively. High biomass and lipid productivities were achieved in outdoor panel PBRs, up to 1.25 and 0.59 g L(-1) day(-1), or 44. 1 and 16.1 g m(-2) day(-1), respectively. A two-stage cultivation strategy was proposed to enhance the algal biomass and lipid production. This is the first comprehensive investigation of both indoor and outdoor photoautotrophic C. protothecoides cultures for oil production, and C. protothecoides CS-41 represents a promising biofuel feedstock worthy of further exploration.


Assuntos
Processos Autotróficos , Chlorella/metabolismo , Lipídeos/química , Óleos/metabolismo , Processos Fototróficos , Processos Autotróficos/efeitos dos fármacos , Processos Autotróficos/efeitos da radiação , Biocombustíveis , Biomassa , Chlorella/efeitos dos fármacos , Chlorella/crescimento & desenvolvimento , Chlorella/efeitos da radiação , Luz , Lipídeos/biossíntese , Nitrogênio/farmacologia , Ácido Oleico/metabolismo , Fósforo/farmacologia , Fotobiorreatores/microbiologia , Processos Fototróficos/efeitos dos fármacos , Processos Fototróficos/efeitos da radiação , Fatores de Tempo , Triglicerídeos/metabolismo
15.
Mol Microbiol ; 93(5): 1066-78, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-25039543

RESUMO

In all photosynthetic organisms, chlorophylls function as light-absorbing photopigments allowing the efficient harvesting of light energy. Chlorophyll biosynthesis recurs in similar ways in anoxygenic phototrophic proteobacteria as well as oxygenic phototrophic cyanobacteria and plants. Here, the biocatalytic conversion of protochlorophyllide to chlorophyllide is catalysed by evolutionary and structurally distinct protochlorophyllide reductases (PORs) in anoxygenic and oxygenic phototrophs. It is commonly assumed that anoxygenic phototrophs only contain oxygen-sensitive dark-operative PORs (DPORs), which catalyse protochlorophyllide reduction independent of the presence of light. In contrast, oxygenic phototrophs additionally (or exclusively) possess oxygen-insensitive but light-dependent PORs (LPORs). Based on this observation it was suggested that light-dependent protochlorophyllide reduction first emerged as a consequence of increased atmospheric oxygen levels caused by oxygenic photosynthesis in cyanobacteria. Here, we provide experimental evidence for the presence of an LPOR in the anoxygenic phototrophic α-proteobacterium Dinoroseobacter shibae DFL12(T). In vitro and in vivo functional assays unequivocally prove light-dependent protochlorophyllide reduction by this enzyme and reveal that LPORs are not restricted to cyanobacteria and plants. Sequence-based phylogenetic analyses reconcile our findings with current hypotheses about the evolution of LPORs by suggesting that the light-dependent enzyme of D. shibae DFL12(T) might have been obtained from cyanobacteria by horizontal gene transfer.


Assuntos
Alphaproteobacteria/enzimologia , Proteínas de Bactérias/metabolismo , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/metabolismo , Alphaproteobacteria/classificação , Alphaproteobacteria/genética , Alphaproteobacteria/isolamento & purificação , Sequência de Aminoácidos , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Biocatálise/efeitos da radiação , Luz , Dados de Sequência Molecular , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/química , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/genética , Oxigênio/metabolismo , Processos Fototróficos/efeitos da radiação , Filogenia , Protoclorifilida/metabolismo , Alinhamento de Sequência , Triticum/microbiologia
16.
Water Res ; 50: 18-26, 2014 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-24361516

RESUMO

The organics and nutrients in industrial and domestic wastewater are increasingly being regarded as a valuable resource for energy and nutrient recovery. Emerging concepts to redesign wastewater treatment as resource recovery systems include the use of different bacteria and algae to partition carbon and nutrients to the particulate phase through assimilation or bio-accumulation. This study evaluates the use of purple phototrophic bacteria (PPB) (also known as purple non-sulphur bacteria or PNSB) for such a biological concentration process through a series of batch tests. The key objectives are to (a) demonstrate consistent selection and enrichment of PPB using infrared light in a non-sterile medium, and (b) achieve effective partitioning of soluble organics, ammonium and phosphate into the PPB culture. PPB were successfully enriched from pre-settled domestic wastewater within 2-3 days and identified as members of the order Rhodobacterales. Under anaerobic conditions with infrared irradiation the enrichment culture was able to simultaneously remove COD (63 ± 5%), NH4-N (99.6%-0.12 ± 0.03 mgN L(-1)) and PO4-P (88%-0.8 ± 0.6 mgP L(-1)) from primary settled domestic wastewater in 24 h. In this experiment, acetate was added as an additional carbon source to demonstrate the maximal nitrogen and phosphorous elimination potential. Almost all the COD removed was assimilated into biomass rather than oxidised to CO2, with the total COD actually increasing during the batch experiments due to phototrophic synthesis. NH4-N and PO4-P were also assimilated by the biomass rather than removed through destructive oxidation or accumulation. The process offers the opportunity to concentrate organics and macronutrients from wastewater in one solids stream that can be anaerobically digested to generate energy and recover nutrients from the concentrated digestate. Technical challenges include the design of a continuous reactor system, as well as efficient delivery of electrons, either through light or chemical sources.


Assuntos
Nitrogênio/isolamento & purificação , Fósforo/isolamento & purificação , Processos Fototróficos , Proteobactérias/metabolismo , Águas Residuárias/microbiologia , Compostos de Amônio/isolamento & purificação , Técnicas de Cultura Celular por Lotes , Biodegradação Ambiental/efeitos da radiação , Análise da Demanda Biológica de Oxigênio , Cor , Hibridização in Situ Fluorescente , Raios Infravermelhos , Fosfatos/isolamento & purificação , Processos Fototróficos/efeitos da radiação , Proteobactérias/efeitos da radiação
17.
Plant Physiol ; 163(2): 1037-46, 2013 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-23922268

RESUMO

Thylakoid membranes are typical and essential features of both chloroplasts and cyanobacteria. While they are crucial for phototrophic growth of cyanobacterial cells, biogenesis of thylakoid membranes is not well understood yet. Dark-grown Synechocystis sp. PCC 6803 cells contain only rudimentary thylakoid membranes but still a relatively high amount of phycobilisomes, inactive photosystem II and active photosystem I centers. After shifting dark-grown Synechocystis sp. PCC 6803 cells into the light, "greening" of Synechocystis sp. PCC 6803 cells, i.e. thylakoid membrane formation and recovery of photosynthetic electron transport reactions, was monitored. Complete restoration of a typical thylakoid membrane system was observed within 24 hours after an initial lag phase of 6 to 8 hours. Furthermore, activation of photosystem II complexes and restoration of a functional photosynthetic electron transport chain appears to be linked to the biogenesis of organized thylakoid membrane pairs.


Assuntos
Complexo de Proteína do Fotossistema II/metabolismo , Synechocystis/citologia , Synechocystis/metabolismo , Tilacoides/metabolismo , Clorofila/metabolismo , Transporte de Elétrons/efeitos da radiação , Processos Heterotróficos/efeitos da radiação , Immunoblotting , Cinética , Luz , Oxigênio/metabolismo , Fotossíntese/efeitos da radiação , Complexo de Proteína do Fotossistema I/metabolismo , Processos Fototróficos/efeitos da radiação , Subunidades Proteicas/metabolismo , Espectrometria de Fluorescência , Synechocystis/efeitos da radiação , Synechocystis/ultraestrutura , Tilacoides/efeitos da radiação , Tilacoides/ultraestrutura , Fatores de Tempo
18.
Bioprocess Biosyst Eng ; 35(1-2): 309-15, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-21909667

RESUMO

The unicellular green microalgae, Haematococcus pluvialis, has been examined as a microbial source for the production of astaxanthin, which has been suggested as a food supplement for humans and is also prescribed as an ingredient in eye drops because of its powerful anti-oxidant properties. In this study, we estimated the effects of the slope of a V-shaped bottom design, the volumetric flow rate of air, height/diameter (H/D) ratio, and diameter of an air sparger on the performance of a photo-bioreactor. These parameters were selected because they are recognized as important factors effecting the mixing that produces increased cell density in the reactor. The mixing effect can be measured by changes in optical density in the bioreactor over a period of time. A 6 L indoor photo-bioreactor was prepared in a short time period of 24 h for the performance study. A bioreactor designed with a V-shaped bottom with a slope of 60° showed an optical density change of 0.052 at 680 nm, which was sixfold less than the change in a photo-bioreactor designed with a flat bottom. Studies exploring the effects of bioreactor configuration and a porous metal sparger with a 10 µm pore size showed the best performance at an H/D ratio of 6:1 and a sparger diameter of 1.3 cm, respectively. The optimal rate of air flow was 0.2 vvm. The indoor culture of microalgae in the photo-bioreactor was subsequently carried for an application study using the optimal values established for the important factors. The indoor culture system was composed of a light source controlled according to cell phase, a carbon dioxide feeder, a bag-type reactor with an H/D ratio of 6:1, and a temperature controller. Results demonstrated the efficient production of microalgal cells and astaxanthin in the amounts of 2.62 g/L and 78.37 mg/L, respectively, when using adequate hydrodynamic mixing. Furthermore, the optimal design of a photo-bioreactor can be applied for the phototropic culturing of other microalgae for mass production.


Assuntos
Técnicas de Cultura de Células/instrumentação , Clorófitas/fisiologia , Clorófitas/efeitos da radiação , Fotobiorreatores/microbiologia , Proliferação de Células/efeitos da radiação , Sobrevivência Celular/efeitos da radiação , Relação Dose-Resposta à Radiação , Desenho de Equipamento , Análise de Falha de Equipamento , Luz , Processos Fototróficos/fisiologia , Processos Fototróficos/efeitos da radiação , Projetos Piloto , Doses de Radiação
19.
Proc Natl Acad Sci U S A ; 108(27): 11280-4, 2011 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-21690384

RESUMO

In many phototrophic microorganisms and plants, chloroplasts change their positions relative to the incident light to achieve optimal photosynthesis. In the case of motile green algae, cells change their swimming direction by switching between positive and negative phototaxis, i.e., swimming toward or away from the light source, depending on environmental and internal conditions. However, little is known about the molecular signals that determine the phototactic direction. Using the green alga Chlamydomonas reinhardtii, we found that cellular reduction-oxidation (redox) poise plays a key role: Cells always exhibited positive phototaxis after treatment with reactive oxygen species (ROS) and always displayed negative phototaxis after treatment with ROS quenchers. The redox-dependent switching of the sign of phototaxis may contribute in turn to the maintenance of cellular redox homeostasis.


Assuntos
Chlamydomonas reinhardtii/fisiologia , Chlamydomonas reinhardtii/efeitos da radiação , Processos Fototróficos/fisiologia , Antioxidantes/farmacologia , Chlamydomonas reinhardtii/efeitos dos fármacos , Óxidos N-Cíclicos/farmacologia , Modelos Biológicos , Movimento/efeitos dos fármacos , Movimento/fisiologia , Movimento/efeitos da radiação , Oxirredução , Processos Fototróficos/efeitos dos fármacos , Processos Fototróficos/efeitos da radiação , Espécies Reativas de Oxigênio/metabolismo , Espécies Reativas de Oxigênio/farmacologia , Transdução de Sinais , Marcadores de Spin
20.
Photochem Photobiol Sci ; 10(8): 1318-25, 2011 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-21655620

RESUMO

Mixotrophic nanoflagellates, that combine photosynthesis and phagotrophy, are important members of planktonic food webs in many aquatic environments depending on the balance among the different carbon and energy sources. We carried out field sampling and laboratory experiments with natural nanoflagellate assemblages from an Andean North-Patagonian lake exposing them or not to UVR, and measuring photosynthetic parameters and bacterivory. The effect of different light treatments on the photosynthetic efficiency was studied by the non-invasive, pulse amplitude-modulated (PAM) fluorescence technique, and bacterivory was assessed with fluorescently labeled bacteria (FLB). Mixotrophic nanoflagellates were clearly dominant (up to 90% of total phytoplankton and 88% of total nanoflagellate abundance), and in the experiments labeled bacteria were observed in more than 75% of mixotrophic cells. These results support the idea that these phytoflagellates were never entirely photosynthetic. The high light : phosphorus ratio and the high C : N : P ratio suggest a strong nutrient limitation towards P. Our results show that both functions, photosynthesis and bacteria ingestion, were simultaneously reduced by the same level of UVR. We estimated that UVR exposure of mixotrophic nanoflagellates reduced photosystem II activity between 23% and 31% while ingestion rates were reduced between 23% and 28%. Therefore, our results suggest that the different cell functions could be concurrently impacted by UVR, implying that patterns and rates of C transfer would be substantially altered in the microbial food web.


Assuntos
Fitoplâncton/efeitos da radiação , Raios Ultravioleta , Bactérias/crescimento & desenvolvimento , Água Doce/microbiologia , Complexo de Proteína do Fotossistema II/química , Complexo de Proteína do Fotossistema II/metabolismo , Processos Fototróficos/efeitos da radiação , Fitoplâncton/fisiologia , Teoria Quântica
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