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1.
Phys Rev Lett ; 123(15): 158101, 2019 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-31702314

RESUMO

Microorganismal motility is often characterized by complex responses to environmental physico-chemical stimuli. Although the biological basis of these responses is often not well understood, their exploitation already promises novel avenues to directly control the motion of living active matter at both the individual and collective level. Here we leverage the phototactic ability of the model microalga Chlamydomonas reinhardtii to precisely control the timing and position of localized cell photoaccumulation, leading to the controlled development of isolated bioconvective plumes. This novel form of photobioconvection allows a precise, fast, and reconfigurable control of the spatiotemporal dynamics of the instability and the ensuing global recirculation, which can be activated and stopped in real time. A simple continuum model accounts for the phototactic response of the suspension and demonstrates how the spatiotemporal dynamics of the illumination field can be used as a simple external switch to produce efficient bio mixing.


Assuntos
Chlamydomonas reinhardtii/fisiologia , Modelos Biológicos , Fotobiologia , Processos Fototróficos
2.
Nat Commun ; 10(1): 4230, 2019 09 17.
Artigo em Inglês | MEDLINE | ID: mdl-31530813

RESUMO

In alkaline soda lakes, concentrated dissolved carbonates establish productive phototrophic microbial mats. Here we show how microbial phototrophs and autotrophs contribute to this exceptional productivity. Amplicon and shotgun DNA sequencing data of microbial mats from four Canadian soda lakes indicate the presence of > 2,000 species of Bacteria and Eukaryotes. We recover metagenome-assembled-genomes for a core microbiome of < 100 abundant bacteria, present in all four lakes. Most of these are related to microbes previously detected in sediments of Asian alkaline lakes, showing that common selection principles drive community assembly from a globally distributed reservoir of alkaliphile biodiversity. Detection of > 7,000 proteins show how phototrophic populations allocate resources to specific processes and occupy complementary niches. Carbon fixation proceeds by the Calvin-Benson-Bassham cycle, in Cyanobacteria, Gammaproteobacteria, and, surprisingly, Gemmatimonadetes. Our study provides insight into soda lake ecology, as well as a template to guide efforts to engineer biotechnology for carbon dioxide conversion.


Assuntos
Bactérias/isolamento & purificação , Lagos/microbiologia , Microbiota , Filogenia , Álcalis/análise , Processos Autotróficos , Bactérias/classificação , Bactérias/genética , Bactérias/efeitos da radiação , Biodiversidade , Canadá , Ciclo do Carbono , Lagos/química , Luz , Processos Fototróficos , Enxofre/metabolismo
3.
Int J Mol Sci ; 20(18)2019 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-31491935

RESUMO

Palmitoleic acid, one scarce omega-7 monounsaturated fatty acid, has important applications in the fields of medicine and health products. Tribonema has been considered as a promising candidate for the production of palmitoleic acid due to its high lipid and palmitoleic acid content and remarkable heterotrophic ability. The high-density heterotrophic cultivation of Tribonema minus was conducted in this work, and the highest biomass of 42.9 g L-1 and a relatively low lipid content of 28.7% were observed. To further enhance the lipid and palmitoleic acid accumulation, induction strategies under two regimes of phototrophy and heterotrophy with different conditions were investigated and compared. Results demonstrated encouraging promotions both by heterotrophic and phototrophic ways, and the final lipid contents reached 41.9% and 49.0%, respectively. In consideration of the time cost, however, the induction under heterotrophic conditions was much more advantageous, by which the highest lipid and palmitoleic acid productivities of 1.77 g L-1 d-1 and 924 mg L-1 d-1 were obtained respectively, with the lipid yield on glucose of 0.26 g g-1.


Assuntos
Clorófitas/metabolismo , Ácidos Graxos Monoinsaturados/metabolismo , Fermentação , Lipídeos/biossíntese , Sementes/metabolismo , Metabolismo dos Lipídeos , Processos Fototróficos
4.
Microbes Environ ; 34(3): 278-292, 2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31413226

RESUMO

Hydrothermal systems, including terrestrial hot springs, contain diverse geochemical conditions that vary over short spatial scales due to progressive interactions between reducing hydrothermal fluids, the oxygenated atmosphere, and, in some cases, seawater. At Jinata Onsen on Shikinejima Island, Japan, an intertidal, anoxic, iron-rich hot spring mixes with the oxygenated atmosphere and seawater over short spatial scales, creating diverse chemical potentials and redox pairs over a distance of ~10 m. We characterized geochemical conditions along the outflow of Jinata Onsen as well as the microbial communities present in biofilms, mats, and mineral crusts along its traverse using 16S rRNA gene amplicon and genome-resolved shotgun metagenomic sequencing. Microbial communities significantly changed downstream as temperatures and dissolved iron concentrations decreased and dissolved oxygen increased. Biomass was more limited near the spring source than downstream, and primary productivity appeared to be fueled by the oxidation of ferrous iron and molecular hydrogen by members of Zetaproteobacteria and Aquificae. The microbial community downstream was dominated by oxygenic Cyanobacteria. Cyanobacteria are abundant and active even at ferrous iron concentrations of ~150 µM, which challenges the idea that iron toxicity limited cyanobacterial expansion in Precambrian oceans. Several novel lineages of Bacteria are also present at Jinata Onsen, including previously uncharacterized members of the phyla Chloroflexi and Calditrichaeota, positioning Jinata Onsen as a valuable site for the future characterization of these clades.


Assuntos
Bactérias/metabolismo , Biodiversidade , Fontes Termais/química , Fontes Termais/microbiologia , Ferro/metabolismo , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , Biomassa , Crescimento Quimioautotrófico , Geografia , Ferro/análise , Metagenômica , Microbiota/genética , Oxigênio/análise , Oxigênio/metabolismo , Processos Fototróficos , Filogenia , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Temperatura Ambiente
5.
Microbes Environ ; 34(3): 304-309, 2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31391357

RESUMO

Chloroflexus aggregans is a thermophilic filamentous anoxygenic phototrophic bacterium frequently found in microbial mats in natural hot springs. C. aggregans often thrives with cyanobacteria that engage in photosynthesis to provide it with an organic substrate; however, it sometimes appears as the dominant phototroph in microbial mats without cyanobacteria. This suggests that C. aggregans has the ability to grow photoautotrophically. However, photoautotrophic growth has not been observed in any cultured strains of C. aggregans. We herein attempted to isolate a photoautotrophic strain from C. aggregansdominated microbial mats in Nakabusa hot spring in Japan. Using an inorganic medium, we succeeded in isolating a new strain that we designated "ACA-12". A phylogenetic analysis based on 16S rRNA gene and 16S-23S rRNA gene internal transcribed spacer (ITS) region sequences revealed that strain ACA-12 was closely related to known C. aggregans strains. Strain ACA-12 showed sulfide consumption along with autotrophic growth under anaerobic light conditions. The deposited elemental sulfur particles observed by microscopy indicated that sulfide oxidation occurred, similar to that in photoautotrophic strains in the related species, C. aurantiacus. Moreover, we found that other strains of C. aggregans, including the type strain, also exhibited a slight photoautotrophic growing ability, whereas strain ACA-12 showed the fastest growth rate. This is the first demonstration of photoautotrophic growth with sulfide in C. aggregans. The present results strongly indicate that C. aggregans is associated with inorganic carbon incorporation using sulfide as an electron donor in hot spring microbial mats.


Assuntos
Chloroflexus/metabolismo , Processos Fototróficos , Sulfetos/metabolismo , Proteínas de Bactérias/genética , Chloroflexus/classificação , Chloroflexus/genética , Chloroflexus/efeitos da radiação , Meios de Cultura/química , DNA Bacteriano/genética , DNA Espaçador Ribossômico/genética , Fontes Termais/microbiologia , Japão , Luz , Oxirredução , Filogenia , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Sulfetos/análise , Enxofre/metabolismo
6.
BMC Bioinformatics ; 20(1): 233, 2019 May 09.
Artigo em Inglês | MEDLINE | ID: mdl-31072303

RESUMO

BACKGROUND: Living organisms need to allocate their limited resources in a manner that optimizes their overall fitness by simultaneously achieving several different biological objectives. Examination of these biological trade-offs can provide invaluable information regarding the biophysical and biochemical bases behind observed cellular phenotypes. A quantitative knowledge of a cell system's critical objectives is also needed for engineering of cellular metabolism, where there is interest in mitigating the fitness costs that may result from human manipulation. RESULTS: To study metabolism in photoheterotrophs, we developed and validated a genome-scale model of metabolism in Rhodopseudomonas palustris, a metabolically versatile gram-negative purple non-sulfur bacterium capable of growing phototrophically on various carbon sources, including inorganic carbon and aromatic compounds. To quantitatively assess trade-offs among a set of important biological objectives during different metabolic growth modes, we used our new model to conduct an 8-dimensional multi-objective flux analysis of metabolism in R. palustris. Our results revealed that phototrophic metabolism in R. palustris is light-limited under anaerobic conditions, regardless of the available carbon source. Under photoheterotrophic conditions, R. palustris prioritizes the optimization of carbon efficiency, followed by ATP production and biomass production rate, in a Pareto-optimal manner. To achieve maximum carbon fixation, cells appear to divert limited energy resources away from growth and toward CO2 fixation, even in the presence of excess reduced carbon. We also found that to achieve the theoretical maximum rate of biomass production, anaerobic metabolism requires import of additional compounds (such as protons) to serve as electron acceptors. Finally, we found that production of hydrogen gas, of potential interest as a candidate biofuel, lowers the cellular growth rates under all circumstances. CONCLUSIONS: Photoheterotrophic metabolism of R. palustris is primarily regulated by the amount of light it can absorb and not the availability of carbon. However, despite carbon's secondary role as a regulating factor, R. palustris' metabolism strives for maximum carbon efficiency, even when this increased efficiency leads to slightly lower growth rates.


Assuntos
Processos Fototróficos/genética , Rodopseudomonas/genética
7.
Arch Microbiol ; 201(6): 795-805, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30868175

RESUMO

This is the comparative investigation of the composition of phototrophic microbial mats developing in sulfide-rich saline Chokrak springs with outflow at the shore of the hypersaline lake Chokrak by means of next-generation sequencing. The springs are characterized by low temperature (~ 15 °C), near-neutral pH (6.7-8.5), and high-sulfide content. In the species composition the benthic microbial communities of Chokrak springs are similar to microbial mats of marine supralittoral and lagoons. Our results showed that salinity limitation had a significant effect on the species composition of benthic microbial communities developing at the outflow of the Chokrak springs. Predominant oxygenic phototrophs belonged to the genera Phormidium, Lyngbya, Leptolyngbya, Geitlerinema, and Arthrospira. Anoxygenic phototrophic bacteria were represented by halophilic green sulfur bacteria Prosthecochloris spp., halotolerant Chlorobaculum sp., as well as marine and extremely halophilic purple bacteria Roseospira, Rhodovibrio, and Halochromatium. Monoculture of a new species of halotolerant anoxygenic filamentous phototrophic bacteria was isolated.


Assuntos
Bactérias/isolamento & purificação , Fontes Termais/microbiologia , Lagos/microbiologia , Microbiota , Sulfetos/metabolismo , Bactérias/classificação , Bactérias/metabolismo , Fontes Termais/análise , Concentração de Íons de Hidrogênio , Lagos/análise , Processos Fototróficos , Filogenia , Salinidade , Sulfetos/análise , Enxofre/análise , Enxofre/metabolismo
8.
ISME J ; 13(8): 1975-1987, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-30914777

RESUMO

We studied the long-term temporal dynamics of the aerobic anoxygenic phototrophic (AAP) bacteria, a relevant functional group in the coastal marine microbial food web, using high-throughput sequencing of the pufM gene coupled with multivariate, time series and co-occurrence analyses at the Blanes Bay Microbial Observatory (NW Mediterranean). Additionally, using metagenomics, we tested whether the used primers captured accurately the seasonality of the most relevant AAP groups. Phylogroup K (Gammaproteobacteria) was the greatest contributor to community structure over all seasons, with phylogroups E and G (Alphaproteobacteria) being prevalent in spring. Diversity indices showed a clear seasonal trend, with maximum values in winter, which was inverse to that of AAP abundance. Multivariate analyses revealed sample clustering by season, with a relevant proportion of the variance explained by day length, temperature, salinity, phototrophic nanoflagellate abundance, chlorophyll a, and silicate concentration. Time series analysis showed robust rhythmic patterns of co-occurrence, but distinct seasonal behaviors within the same phylogroup, and even within different amplicon sequence variants (ASVs) conforming the same operational taxonomic unit (OTU). Altogether, our results picture the AAP assemblage as highly seasonal and recurrent but containing ecotypes showing distinctive temporal niche partitioning, rather than being a cohesive functional group.


Assuntos
Bactérias Aeróbias/metabolismo , Água do Mar/microbiologia , Bactérias Aeróbias/classificação , Bactérias Aeróbias/genética , Bactérias Aeróbias/isolamento & purificação , Clorofila A/metabolismo , Processos Fototróficos , Estações do Ano , Temperatura Ambiente
9.
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
10.
PLoS Genet ; 15(3): e1008047, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30875368

RESUMO

Large GTPases of the Dynamin Related Proteins (DRP) family shape lipid bilayers through membrane fission or fusion processes. Despite the highly organized photosynthetic membranes of thylakoids, a single DRP is known to be targeted inside the chloroplast. Fzl from the land plant Arabidopsis thaliana is inserted in the inner envelope and thylakoid membranes to regulate their morphology. Fzl may promote the fusion of thylakoids but this remains to be proven. Moreover, the physiological requirement for fusing thylakoids is currently unknown. Here, we find that the unicellular microalga Chlamydomonas reinhardtii encodes an Fzl ortholog (CrFzl) that is localized in the chloroplast where it is soluble. To explore its function, the CRISPR/Cas9 technology was employed to generate multiple CrFzl knock out strains. Phenotypic analyzes revealed a specific requirement of CrFzl for survival upon light stress. Consistent with this, strong irradiance lead to increased photoinhibition of photosynthesis in mutant cells. Fluorescence and electron microscopy analysis demonstrated that upon exposure to high light, CrFzl mutants show defects in chloroplast morphology but also large cytosolic vacuoles in close contact with the plastid. We further observe that strong irradiance induces an increased recruitment of the DRP to thylakoid membranes. Most importantly, we show that CrFzl is required for the fusion of thylakoids during mating. Together, our results suggest that thylakoids fusion may be necessary for resistance to light stress.


Assuntos
Proteínas de Algas/metabolismo , Chlamydomonas reinhardtii/metabolismo , GTP Fosfo-Hidrolases/metabolismo , Tilacoides/metabolismo , Proteínas de Algas/genética , Sistemas CRISPR-Cas , Chlamydomonas reinhardtii/genética , Chlamydomonas reinhardtii/efeitos da radiação , Cloroplastos/metabolismo , Dinaminas/genética , Dinaminas/metabolismo , GTP Fosfo-Hidrolases/genética , Técnicas de Inativação de Genes , Luz , Fusão de Membrana , Microscopia Eletrônica de Transmissão , Mutação , Processos Fototróficos , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Estresse Fisiológico , Tilacoides/efeitos da radiação , Tilacoides/ultraestrutura
11.
Nat Commun ; 10(1): 1355, 2019 03 22.
Artigo em Inglês | MEDLINE | ID: mdl-30902976

RESUMO

Extracellular electron uptake (EEU) is the ability of microbes to take up electrons from solid-phase conductive substances such as metal oxides. EEU is performed by prevalent phototrophic bacterial genera, but the electron transfer pathways and the physiological electron sinks are poorly understood. Here we show that electrons enter the photosynthetic electron transport chain during EEU in the phototrophic bacterium Rhodopseudomonas palustris TIE-1. Cathodic electron flow is also correlated with a highly reducing intracellular redox environment. We show that reducing equivalents are used for carbon dioxide (CO2) fixation, which is the primary electron sink. Deletion of the genes encoding ruBisCO (the CO2-fixing enzyme of the Calvin-Benson-Bassham cycle) leads to a 90% reduction in EEU. This work shows that phototrophs can directly use solid-phase conductive substances for electron transfer, energy transduction, and CO2 fixation.


Assuntos
Ciclo do Carbono , Dióxido de Carbono/metabolismo , Elétrons , Espaço Extracelular/metabolismo , Processos Fototróficos , Rodopseudomonas/metabolismo , Hidrogênio/metabolismo , Espaço Intracelular/metabolismo , Modelos Biológicos , Oxirredução , Fotossíntese , Rodopseudomonas/crescimento & desenvolvimento , Ribulose-Bifosfato Carboxilase/metabolismo
12.
Antonie Van Leeuwenhoek ; 112(8): 1169-1175, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30863942

RESUMO

The genus Tabrizicola with its type species and strain Tabrizicola aquatica RCRI19T was previously described as a purely chemotrophic genus of Gram-negative, aerobic, non-motile and rod-shaped bacteria. With the present study, we expand the description of the metabolic capabilities of this genus and the T. aquatica type strain to include chlorophyll-dependent phototrophy. Our results confirmed that T. aquatica, does not grow under anaerobic photoautotrophic or photoheterotrophic conditions. However, the presence of the photosynthesis-related genes pufL and pufM could be demonstrated in the genomes of several Tabrizicola strains. Additionally, photosynthetic pigments (bacteriochlorophyll a) were formed under aerobic, heterotrophic and low light conditions in T. aquatica strain RCRI19T. Furthermore, all the genes necessary for a fully operational photosynthetic apparatus and bacteriochlorophyll a are present in the T. aquatica type strain genome. Therefore, we suggest categorising T. aquatica RCRI19T, isolated from freshwater environment of Qurugöl Lake, as an aerobic anoxygenic phototrophic (AAP) bacterium.


Assuntos
Água Doce/microbiologia , Processos Fototróficos , Rhodobacteraceae/classificação , Rhodobacteraceae/fisiologia , Aerobiose , Animais , Clorofila/análise , Luz , Redes e Vias Metabólicas/genética , Rhodobacteraceae/genética , Rhodobacteraceae/isolamento & purificação
13.
FEMS Microbiol Lett ; 366(5)2019 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-30801645

RESUMO

In this article, we present the description of a novel mesophilic phototrophic Chloroflexi bacterium, 'Candidatus Viridilinea mediisalina' Kir15-3F. We have isolated an anaerobic, highly enriched culture of this bacterium from the Kiran soda lake (Siberia) and optimized its cultivation. Metagenomic sequencing revealed that 'Ca. Viridilinea mediisalina' Kir15-3F is a bacteriochlorophyll-containing Chloroflexi bacterium in the enrichment culture. Fluorescent in situ hybridisation demonstrated a link between the phenotype described here and the 'Ca. Viridilinea mediisalina' Kir15-3F genome. Spectrophotometry and high-performance liquid chromatography analyses showed the presence of bacteriochlorophylls d, c and a, as well as lycopene, γ-carotene and ß-carotene. Transmission electron microscopy showed chlorosomes, gas vesicles, polyhydroxyalkanoate-like and polyphosphate-like granules. Our results illustrated that 'Ca. Viridilinea mediisalina' Kir15-3F is an alkaliphilic, salt-tolerant, obligately mesophilic, anaerobic, phototrophic bacterium. The genome sequences lack genes of the Calvin cycle and a sulphide:quinone reductase gene for sulphide oxidation. Owing to the lack of an axenic culture and based on the genomic and phenotypic data, we have presented the description of the bacterium in the Candidatus category.


Assuntos
Chloroflexi/classificação , Chloroflexi/metabolismo , Lagos/microbiologia , Processos Fototróficos , Bacterioclorofilas/análise , Carotenoides/análise , Chloroflexi/citologia , Chloroflexi/fisiologia , DNA Bacteriano/genética , Genoma Bacteriano/genética , Lagos/química , Metagenômica , Filogenia , RNA Ribossômico 16S/genética , Sais/metabolismo , Análise de Sequência de DNA , Sibéria , Microbiologia da Água
14.
Water Res ; 152: 138-147, 2019 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-30665160

RESUMO

Nutrient losses in our food chain severely surpass our planetary boundaries. Resource recovery can contribute to mitigation, for instance through converting wastewater resources to microbial protein for animal feed. Wastewater typically holds a complex mixture of organics, posing a challenge to selectively produce heterotrophic biomass. Ensuring the product's quality could be achieved by anaerobic generation of volatile fatty acids (VFAs) followed by photoheterotrophic production of purple non-sulfur bacteria (PNSB) with infrared light. This study aimed to determine the most suitable PNSB culture for VFA conversion and map the effect of acetate, propionate, butyrate and a VFA mixture on growth and biomass yield. Six cultures were screened in batch: (i) Rhodopseudomonas palustris, (ii) Rhodobacter sphaeroides, (iii) Rhodospirillum rubrum, (iv) a 3-species synthetic community (i+ii+iii), (v) a community enriched on VFA holding Rb. capsulatus, and (vi) Rb. capsulatus (isolate 'v'). The VFA mixture elevated growth rates with a factor 1.3-2.5 compared to individual VFA. Rb. capsulatus showed the highest growth rates: 1.8-2.2 d-1 (enriched) and 2.3-3.8 d-1 (isolated). In a photobioreactor (PBR) inoculated with the Rb. capsulatus enrichment, decreasing sludge retention time (SRT) yielded lower biomass concentrations, yet increased productivities, reaching 1.7 g dry weight (DW) L-1 d-1, the highest phototrophic rate reported thus far, and a growth rate of up to 5 d-1. PNSB represented 26-57% of the community and the diversity index was low (3-7), with a dominance of Rhodopseudomonas at long SRT and Rhodobacter at short SRT. The biomass yield for all cultures, in batch and reactor cultivation, approached 1 g CODBiomass g-1 CODRemoved. An economic estimation for a two-stage approach on brewery wastewater (load 2427 kg COD d-1) showed that 0.5 d SRT allowed for the lowest production cost (€ 10 kg-1 DW; equal shares for capex and opex). The findings strengthen the potential for a novel two-stage approach for resource recovery from industrial wastewater, enabling high-rate PNSB production.


Assuntos
Proteobactérias , Águas Residuárias , Ácidos Graxos Voláteis , Cinética , Processos Fototróficos
15.
Nat Commun ; 10(1): 271, 2019 01 17.
Artigo em Inglês | MEDLINE | ID: mdl-30655514

RESUMO

Despite their discovery over 25 years ago, the Marine Group II Euryarchaea (MGII) remain a difficult group of organisms to study, lacking cultured isolates and genome references. The MGII have been identified in marine samples from around the world, and evidence supports a photoheterotrophic lifestyle combining phototrophy via proteorhodopsins with the remineralization of high molecular weight organic matter. Divided between two clades, the MGII have distinct ecological patterns that are not understood based on the limited number of available genomes. Here, I present a comparative genomic analysis of 250 MGII genomes, providing a comprehensive investigation of these mesophilic archaea. This analysis identifies 17 distinct subclades including nine subclades that previously lacked reference genomes. The metabolic potential and distribution of the MGII genera reveals distinct roles in the environment, identifying algal-saccharide-degrading coastal subclades, protein-degrading oligotrophic surface ocean subclades, and mesopelagic subclades lacking proteorhodopsins, common in all other subclades.


Assuntos
Organismos Aquáticos/metabolismo , Ecologia/métodos , Euryarchaeota/metabolismo , Genoma Arqueal/genética , Metagenômica , Organismos Aquáticos/genética , Euryarchaeota/genética , Genômica , Processos Fototróficos , Filogenia , Rodopsinas Microbianas/metabolismo , Água do Mar/microbiologia
16.
Int J Biol Macromol ; 126: 1085-1092, 2019 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-30610947

RESUMO

Polyhydroxyalkanoates (PHAs) production with phototrophic mixed cultures (PMCs) has been recently proposed. These cultures can be selected under the permanent presence of carbon and the PHA production can be enhanced in subsequent accumulation steps. To optimize the PHA production in accumulator reactors, this work evaluated the impact of 1) initial acetate concentration, 2) light intensity, 3) removal of residual nitrogen on the culture performance. Results indicate that low acetate concentration (<30 CmM) and specific light intensities around 20 W/gX are optimal operating conditions that lead to high polyhydroxybutyrate (PHB) storage yields (0.83 ±â€¯0.07 Cmol-PHB/Cmol-Acet) and specific PHB production rates of 2.21 ±â€¯0.07 Cmol-PHB/Cmol X d. This rate is three times higher than previously registered in non-optimized accumulation tests and enabled a PHA content increase from 15 to 30% in <4 h. Also, it was shown for the first time, the capability of a PMC to use a real waste, fermented cheese whey, to produce PHA with a hydroxyvalerate (HV) content of 12%. These results confirm that fermented wastes can be used as substrates for PHA production with PMCs and that the energy levels in sunlight that lead to specific light intensities from 10 to 20 W/gX are sufficient to drive phototrophic PHA production processes.


Assuntos
Reatores Biológicos , Processos Fototróficos , Poli-Hidroxialcanoatos/biossíntese , Acetatos/análise , Queijo , Fermentação , Cinética , Luz , Nitrogênio/isolamento & purificação , Soro do Leite/química
17.
Environ Pollut ; 244: 314-322, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30343232

RESUMO

Silver ions are among the predominant anthropogenic introduced pollutants in aquatic systems. As silver has effects on species at all trophic levels the community composition in aquatic habitats can be changed as a result of silver stress. The response of planktonic protists to environmental stressors is particularly important as they act both as producers and consumers in complex planktonic communities. Chrysomonad flagellates are of major interest, since this group includes heterotrophic, mixotrophic and phototrophic taxa, and therefore allows analysis of silver stress in organisms with contrasting nutritional strategies independent of a potential taxonomic bias. In a series of lab experiments, we compared the response of different trophic chrysophyte strains to low (5 µg L-1), medium (10 µg L-1) and high (20 µg L-1) nominal Ag concentrations in combination with changes in temperature and light intensity (phototrophs), temperature and food concentration (heterotrophs), or a combination of the above settings (mixotrophs). All tested strains were negatively affected by silver in their growth rates. The phototrophic strains reacted strongly to silver stress, whereas light intensity and temperature had only minor effects on growth rates. For heterotrophic strains, high food concentration toned down the effect of silver, whereas temperatures outside the growth optimum had a combined stress effect. The mixotrophic strains reacted differently depending on whether their nutritional mode was dominated by heterotrophy or by phototrophy. The precise response pattern across all variables was uniquely different for every single species we tested. The present work contributes to a deeper understanding of the effects of environmental stressors on complex planktonic communities. It indicates that silver will negatively impact planktonic communities and may create shifts in their composition and functioning.


Assuntos
Eucariotos/crescimento & desenvolvimento , Processos Heterotróficos/efeitos dos fármacos , Invertebrados/crescimento & desenvolvimento , Processos Fototróficos/efeitos dos fármacos , Plâncton/crescimento & desenvolvimento , Prata/toxicidade , Poluentes Químicos da Água/toxicidade , Animais , Ecossistema , Luz
18.
Photosynth Res ; 140(3): 275-287, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30415289

RESUMO

We previously found that glycerol is required for heterotrophic growth in the unicellular red alga Cyanidioschyzon merolae. Here, we analyzed heterotrophically grown cells in more detail. Sugars or other organic substances did not support the growth in the dark. The growth rate was 0.4 divisions day-1 in the presence of 400 mM glycerol, in contrast with 0.5 divisions day-1 in the phototrophic growth. The growth continued until the sixth division. Unlimited heterotrophic growth was possible in the medium containing DCMU and glycerol in the light. Light-activated heterotrophic culture in which cells were irradiated by intermittent light also continued without an apparent limit. In the heterotrophic culture in the dark, chlorophyll content drastically decreased, as a result of inability of dark chlorophyll synthesis. Photosynthetic activity gradually decreased over 10 days, and finally lost after 19 days. Low-temperature fluorescence measurement and immunoblot analysis showed that this decline in photosynthetic activity was mainly due to the loss of Photosystem I, while the levels of Photosystem II and phycobilisomes were maintained. Accumulated triacylglycerol was lost during the heterotrophic growth, while keeping the overall lipid composition. Observation by transmission electron microscopy revealed that a part of thylakoid membranes turned into pentagonal tubular structures, on which five rows of phycobilisomes were aligned. This might be a structure that compactly conserve phycobilisomes and Photosystem II in an inactive state, probably as a stock of carbon and nitrogen. These results suggest that C. merolae has a unique strategy of heterotrophic growth, distinct from those found in other red algae.


Assuntos
Processos Heterotróficos , Complexo de Proteína do Fotossistema I/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Ficobilissomas/metabolismo , Rodófitas/fisiologia , Clorofila/metabolismo , Fluorescência , Luz , Nitrogênio/metabolismo , Processos Fototróficos , Rodófitas/crescimento & desenvolvimento , Rodófitas/efeitos da radiação , Rodófitas/ultraestrutura , Tilacoides/metabolismo , Tilacoides/ultraestrutura
19.
FEMS Microbiol Ecol ; 95(1)2019 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-30380056

RESUMO

Microbial mats and stromatolites are widespread in Hamelin Pool, Shark Bay, however the phototrophic capacity of these systems is unknown. This study has determined the optical properties and light-harvesting potential of these mats with light microsensors. These characteristics were linked via a combination of 16S rDNA sequencing, pigment analyses and hyperspectral imaging. Local scalar irradiance was elevated over the incident downwelling irradiance by 1.5-fold, suggesting light trapping and strong scattering by the mats. Visible light (400-700 nm) penetrated to a depth of 2 mm, whereas near-infrared light (700-800 nm) penetrated to at least 6 mm. Chlorophyll a and bacteriochlorophyll a (Bchl a) were found to be the dominant photosynthetic pigments present, with BChl a peaking at the subsurface (2-4 mm). Detailed 16S rDNA analyses revealed the presence of putative Chl f-containing Halomicronema sp. and photosynthetic members primarily decreased from the mat surface down to a depth of 6 mm. Data indicated high abundances of some pigments and phototrophic organisms in deeper layers of the mats (6-16 mm). It is proposed that the photosynthetic bacteria present in this system undergo unique adaptations to lower light conditions below the mat surface, and that phototrophic metabolisms are major contributors to ecosystem function.


Assuntos
Cianobactérias/metabolismo , Cianobactérias/efeitos da radiação , Fotossíntese , Pigmentos Biológicos/metabolismo , Água do Mar/microbiologia , Austrália , Clorofila A/metabolismo , Cianobactérias/classificação , Cianobactérias/genética , Ecossistema , Luz , Processos Fototróficos
20.
J Gen Appl Microbiol ; 65(1): 39-46, 2019 Mar 08.
Artigo em Inglês | MEDLINE | ID: mdl-29998926

RESUMO

The clonal strains, phycoerythrin(PE)-rich- and PE-poor strains, of the unicellular, fresh water cyanobacterium Aphanothece sacrum (Suringar) Okada (Suizenji Nori, in Japanese) were isolated from traditional open-air aquafarms in Japan. A. sacrum appeared to be oligotrophic on the basis of its growth characteristics. The optimum temperature for growth was around 20°C. Maximum growth and biomass increase at 20°C was obtained under light intensities between 40 to 80 µmol m-2 s-1 (fluorescent lamps, 12 h light/12 h dark cycles) and between 40 to 120 µmol m-2 s-1 for PE-rich and PE-poor strains, respectively, of A. sacrum . Purified exopolysaccharide (EPS) of A. sacrum has a molecular weight of ca. 104 kDa with five major monosaccharides (glucose, xylose, rhamnose, galactose and mannose; ≥85 mol%). We also deciphered the whole genome sequence of the two strains of A. sacrum. The putative genes involved in the polymerization, chain length control, and export of EPS would contribute to understand the biosynthetic process of their extremely high molecular weight EPS. The putative genes encoding Wzx-Wzy-Wzz- and Wza-Wzb-Wzc were conserved in the A. sacrum strains FPU1 and FPU3. This result suggests that the Wzy-dependent pathway participates in the EPS production of A. sacrum.


Assuntos
Cianobactérias/química , Água Doce/microbiologia , Polissacarídeos Bacterianos/genética , Polissacarídeos Bacterianos/fisiologia , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Transporte Biológico , Cianobactérias/classificação , Cianobactérias/genética , Cianobactérias/crescimento & desenvolvimento , Genoma Bacteriano/genética , Luz , Peso Molecular , Monossacarídeos , Processos Fototróficos , Filogenia , Polimerização , Polissacarídeos Bacterianos/biossíntese , Polissacarídeos Bacterianos/química , RNA Ribossômico 16S/genética , Análise de Sequência , Temperatura Ambiente
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