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1.
Nature ; 627(8005): 915-922, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38480893

RESUMO

Scientific exploration of phototrophic bacteria over nearly 200 years has revealed large phylogenetic gaps between known phototrophic groups that limit understanding of how phototrophy evolved and diversified1,2. Here, through Boreal Shield lake water incubations, we cultivated an anoxygenic phototrophic bacterium from a previously unknown order within the Chloroflexota phylum that represents a highly novel transition form in the evolution of photosynthesis. Unlike all other known phototrophs, this bacterium uses a type I reaction centre (RCI) for light energy conversion yet belongs to the same bacterial phylum as organisms that use a type II reaction centre (RCII) for phototrophy. Using physiological, phylogenomic and environmental metatranscriptomic data, we demonstrate active RCI-utilizing metabolism by the strain alongside usage of chlorosomes3 and bacteriochlorophylls4 related to those of RCII-utilizing Chloroflexota members. Despite using different reaction centres, our phylogenomic data provide strong evidence that RCI-utilizing and RCII-utilizing Chloroflexia members inherited phototrophy from a most recent common phototrophic ancestor. The Chloroflexota phylum preserves an evolutionary record of the use of contrasting phototrophic modes among genetically related bacteria, giving new context for exploring the diversification of phototrophy on Earth.


Assuntos
Bactérias , Complexo de Proteína do Fotossistema I , Processos Fototróficos , Bactérias/química , Bactérias/classificação , Bactérias/genética , Bactérias/metabolismo , Bacterioclorofilas/metabolismo , Lagos/microbiologia , Fotossíntese , Complexo de Proteína do Fotossistema I/metabolismo , Filogenia , Anaerobiose , Complexo de Proteína do Fotossistema II/metabolismo , Perfilação da Expressão Gênica
2.
Microbiome ; 12(1): 65, 2024 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-38539229

RESUMO

BACKGROUND: Aerobic anoxygenic phototrophic (AAP) bacteria are heterotrophic bacteria that supply their metabolism with light energy harvested by bacteriochlorophyll-a-containing reaction centers. Despite their substantial contribution to bacterial biomass, microbial food webs, and carbon cycle, their phenology in freshwater lakes remains unknown. Hence, we investigated seasonal variations of AAP abundance and community composition biweekly across 3 years in a temperate, meso-oligotrophic freshwater lake. RESULTS: AAP bacteria displayed a clear seasonal trend with a spring maximum following the bloom of phytoplankton and a secondary maximum in autumn. As the AAP bacteria represent a highly diverse assemblage of species, we followed their seasonal succession using the amplicon sequencing of the pufM marker gene. To enhance the accuracy of the taxonomic assignment, we developed new pufM primers that generate longer amplicons and compiled the currently largest database of pufM genes, comprising 3633 reference sequences spanning all phyla known to contain AAP species. With this novel resource, we demonstrated that the majority of the species appeared during specific phases of the seasonal cycle, with less than 2% of AAP species detected during the whole year. AAP community presented an indigenous freshwater nature characterized by high resilience and heterogenic adaptations to varying conditions of the freshwater environment. CONCLUSIONS: Our findings highlight the substantial contribution of AAP bacteria to the carbon flow and ecological dynamics of lakes and unveil a recurrent and dynamic seasonal succession of the AAP community. By integrating this information with the indicator of primary production (Chlorophyll-a) and existing ecological models, we show that AAP bacteria play a pivotal role in the recycling of dissolved organic matter released during spring phytoplankton bloom. We suggest a potential role of AAP bacteria within the context of the PEG model and their consideration in further ecological models.


Assuntos
Lagos , Processos Fototróficos , Lagos/microbiologia , Bactérias/genética , Biomassa , Bactérias Aeróbias/genética , Bactérias Aeróbias/metabolismo , Fitoplâncton/genética
3.
Am Nat ; 202(4): 458-470, 2023 10.
Artigo em Inglês | MEDLINE | ID: mdl-37792914

RESUMO

AbstractAcquired photosynthesis transforms genotypically heterotrophic lineages into autotrophs. Transient acquisitions of eukaryotic chloroplasts may provide key evolutionary insight into the endosymbiosis process-the hypothesized mechanism by which eukaryotic cells obtained new functions via organelle retention. Here, we use an eco-evolutionary model to study the environmental conditions under which chloroplast retention is evolutionarily favorable. We focus on kleptoplastidic lineages-which steal functional chloroplasts from their prey-as hypothetical evolutionary intermediates. Our adaptive dynamics analysis reveals a spectrum of evolutionarily stable strategies ranging from phagotrophy to phototrophy to obligate kleptoplasty. Our model suggests that a low-light niche and weak (or absent) trade-offs between chloroplast retention and overall digestive ability favor the evolution of phototrophy. In contrast, when consumers experience strong trade-offs, obligate kleptoplasty emerges as an evolutionary end point. Therefore, the preevolved trade-offs that underlie an evolving lineage's physiology will likely constrain its evolutionary trajectory.


Assuntos
Eucariotos , Processos Fototróficos , Processos Fototróficos/fisiologia , Eucariotos/fisiologia , Fotossíntese , Cloroplastos/metabolismo , Processos Heterotróficos , Evolução Biológica
4.
Harmful Algae ; 127: 102483, 2023 08.
Artigo em Inglês | MEDLINE | ID: mdl-37544668

RESUMO

Many harmful algae are mixoplanktonic, i.e. they combine phototrophy and phagotrophy, and this ability may explain their ecological success, especially when environmental conditions are not optimal for autotrophic growth. In this study, laboratory experiments were conducted with the mixotrophic and ichthyotoxic haptophyte Prymnesium parvum (strain CCAP 946/6) to test the effects of phosphorus (P) sufficiency and deficiency on its growth rate, phagotrophic and lytic activities. P-deficient P. parvum cultures were grown without or with addition of P in the form of inorganic phosphorus (nutrients) and/or living algal prey (i.e. the cryptophyte Teleaulax amphioxeia). The ingestion rate of P. parvum and prey mortality rate were calculated using flow cytometry measurements based on pigment-derived-fluorescence to distinguish between prey, predators and digesting predators. The first aim of the study was to develop a method taking into account the rate of digestion, allowing the calculation of ingestion rates over a two-week period. Growth rates of P. parvum were higher in the treatments with live prey, irrespective of the concentration of inorganic P, and maximum growth rates were found when both inorganic and organic P in form of prey were added (0.79 ± 0.07 d-1). In addition, the mortality rate of T. amphioxeia induced by lytic compounds was 0.2 ± 0.02 d-1 in the P-deficient treatment, while no mortality was observed under P-sufficiency in the present experiments. This study also revealed the mortality due to cell lysis exceeded that of prey ingestion. Therefore, additional experiments were conducted with lysed prey cells. When grown with debris from prey cells, the mean growth rate of P. parvum was similar to monocultures without additions of prey debris (0.30 ± 0.1 vs. 0.38 ± 0.03 d-1), suggesting that P. parvum is able to grow on prey debris, but not as fast as with live prey. These results provide the first quantitative evidence over two weeks of experiment that ingestion of organic P in the form of living prey and/or debris of prey plays an important role in P. parvum growth and may explain its ecological success in a nutrient-limited environments.


Assuntos
Haptófitas , Fósforo/farmacologia , Criptófitas , Processos Autotróficos , Processos Fototróficos
5.
ISME J ; 17(7): 1063-1073, 2023 07.
Artigo em Inglês | MEDLINE | ID: mdl-37120702

RESUMO

Rhodopsin photosystems convert light energy into electrochemical gradients used by the cell to produce ATP, or for other energy-demanding processes. While these photosystems are widespread in the ocean and have been identified in diverse microbial taxonomic groups, their physiological role in vivo has only been studied in few marine bacterial strains. Recent metagenomic studies revealed the presence of rhodopsin genes in the understudied Verrucomicrobiota phylum, yet their distribution within different Verrucomicrobiota lineages, their diversity, and function remain unknown. In this study, we show that more than 7% of Verrucomicrobiota genomes (n = 2916) harbor rhodopsins of different types. Furthermore, we describe the first two cultivated rhodopsin-containing strains, one harboring a proteorhodopsin gene and the other a xanthorhodopsin gene, allowing us to characterize their physiology under laboratory-controlled conditions. The strains were isolated in a previous study from the Eastern Mediterranean Sea and read mapping of 16S rRNA gene amplicons showed the highest abundances of these strains at the deep chlorophyll maximum (source of their inoculum) in winter and spring, with a substantial decrease in summer. Genomic analysis of the isolates suggests that motility and degradation of organic material, both energy demanding functions, may be supported by rhodopsin phototrophy in Verrucomicrobiota. Under culture conditions, we show that rhodopsin phototrophy occurs under carbon starvation, with light-mediated energy generation supporting sugar transport into the cells. Overall, this study suggests that photoheterotrophic Verrucomicrobiota may occupy an ecological niche where energy harvested from light enables bacterial motility toward organic matter and supports nutrient uptake.


Assuntos
Bactérias , Rodopsina , Rodopsina/genética , Rodopsina/metabolismo , RNA Ribossômico 16S/genética , RNA Ribossômico 16S/metabolismo , Bactérias/genética , Processos Fototróficos , Transporte Biológico , Rodopsinas Microbianas/genética , Rodopsinas Microbianas/metabolismo , Filogenia
6.
Sci Rep ; 13(1): 6900, 2023 04 27.
Artigo em Inglês | MEDLINE | ID: mdl-37106077

RESUMO

With climate change, oceans are becoming increasingly nutrient limited, favouring growth of prokaryotic picoplankton at the expense of the larger protist plankton whose growth support higher trophic levels. Constitutive mixoplankton (CM), microalgal plankton with innate phototrophic capability coupled with phagotrophy, graze on these picoplankton, indirectly exploiting the excellent resource acquisition abilities of the prokaryotes. However, feeding rates can be very low (e.g., a few bacteria d-1). For the first time, the significance of such low consumption rates has been quantified. We find that while prokaryote-carbon (C) supply to CM grown at non-limiting light was so low that it may appear insignificant (< 10%), contributions of nitrogen (N) and phosphorus (P) from ingestions of 1-12 prokaryotes d-1 were significant. Under limiting light, contributions of ingested C increased, also raising the contributions of N and P. The order of nutritional importance for CM growth from predation was P > N > C. Further, provision of N through internal recycling of ingested prey-N stimulates C-fixation through photosynthesis. Importantly, coupled photo-phago-mixoplanktonic activity improved CM resource affinities for both inorganic and prey-bound nutrients, enhancing the nutritional status and competitiveness of mixoplankton. With warming oceans, with increased prokaryote abundance, we expect CM to exhibit more phagotrophy.


Assuntos
Fotossíntese , Processos Fototróficos , Plâncton , Eucariotos , Oceanos e Mares
7.
Nature ; 615(7952): 535-540, 2023 03.
Artigo em Inglês | MEDLINE | ID: mdl-36859551

RESUMO

Energy transfer from light-harvesting ketocarotenoids to the light-driven proton pump xanthorhodopsins has been previously demonstrated in two unique cases: an extreme halophilic bacterium1 and a terrestrial cyanobacterium2. Attempts to find carotenoids that bind and transfer energy to abundant rhodopsin proton pumps3 from marine photoheterotrophs have thus far failed4-6. Here we detected light energy transfer from the widespread hydroxylated carotenoids zeaxanthin and lutein to the retinal moiety of xanthorhodopsins and proteorhodopsins using functional metagenomics combined with chromophore extraction from the environment. The light-harvesting carotenoids transfer up to 42% of the harvested energy in the violet- or blue-light range to the green-light absorbing retinal chromophore. Our data suggest that these antennas may have a substantial effect on rhodopsin phototrophy in the world's lakes, seas and oceans. However, the functional implications of our findings are yet to be discovered.


Assuntos
Organismos Aquáticos , Processos Fototróficos , Bombas de Próton , Rodopsinas Microbianas , Organismos Aquáticos/metabolismo , Organismos Aquáticos/efeitos da radiação , Bactérias/metabolismo , Bactérias/efeitos da radiação , Carotenoides/metabolismo , Cor , Cianobactérias/metabolismo , Cianobactérias/efeitos da radiação , Processos Heterotróficos/efeitos da radiação , Luz , Oceanos e Mares , Processos Fototróficos/efeitos da radiação , Bombas de Próton/metabolismo , Bombas de Próton/efeitos da radiação , Rodopsinas Microbianas/metabolismo , Rodopsinas Microbianas/efeitos da radiação , Zeaxantinas/metabolismo , Zeaxantinas/efeitos da radiação , Luteína/metabolismo , Luteína/efeitos da radiação , Metagenoma , Lagos
8.
Trends Microbiol ; 31(4): 326-328, 2023 04.
Artigo em Inglês | MEDLINE | ID: mdl-36822951

RESUMO

Despite solid, growing genomic evidence for bacteria practicing bacteriochlorophyll and rhodopsin-based dual phototrophy, direct physiological proof has been lacking for over a decade until Kopejtka et al. recently solved the puzzle in an Alpine psychrophilic bacterium. Here, I highlight conceptual developments and address an overlooked, ecologically important phototrophic byproduct - heat.


Assuntos
Bactérias , Processos Fototróficos , Bactérias/genética , Genômica
9.
Environ Microbiol Rep ; 15(1): 60-71, 2023 02.
Artigo em Inglês | MEDLINE | ID: mdl-36507772

RESUMO

Aerobic anoxygenic photoheterotrophic (AAP) bacteria represent a functional group of prokaryotic organisms that harvests light energy using bacteriochlorophyll-containing photosynthetic reaction centers. They represent an active and rapidly growing component of freshwater bacterioplankton, with the highest numbers observed usually in summer. Species diversity of freshwater AAP bacteria has been studied before in lakes, but its seasonal dynamics remain unknown. In this report, we analysed temporal changes in the composition of the phototrophic community in an oligo-mesotrophic freshwater lake using amplicon sequencing of the pufM marker gene. The AAP community was dominated by phototrophic Gammaproteobacteria and Alphaproteobacteria, with smaller contribution of phototrophic Chloroflexota and Gemmatimonadota. Phototrophic Eremiobacteriota or members of Myxococcota were not detected. Interestingly, some AAP taxa, such as Limnohabitans, Rhodoferax, Rhodobacterales or Rhizobiales, were permanently present over the sampling period, while others, such as Sphingomonadales, Rhodospirillales or Caulobacterales appeared only transiently. The environmental factors that best explain the seasonal changes in AAP community were temperature, concentrations of oxygen and dissolved organic matter.


Assuntos
Alphaproteobacteria , Gammaproteobacteria , Lagos/microbiologia , Bactérias Aeróbias/genética , Alphaproteobacteria/genética , Processos Fototróficos
10.
PLoS One ; 17(8): e0270187, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35913911

RESUMO

While most productivity on the surface of the Earth today is fueled by oxygenic photosynthesis, for much of Earth history it is thought that anoxygenic photosynthesis-using compounds like ferrous iron or sulfide as electron donors-drove most global carbon fixation. Anoxygenic photosynthesis is still performed by diverse bacteria in niche environments today. Of these, the Chlorobi (formerly green sulfur bacteria) are often interpreted as being particularly ancient and are frequently proposed to have fueled the biosphere during late Archean and early Paleoproterozoic time before the rise of oxygenic photosynthesis. Here, we perform comparative genomic, phylogenetic, and molecular clock analyses to determine the antiquity of the Chlorobi and their characteristic phenotypes. We show that contrary to common assumptions, the Chlorobi clade is relatively young, with anoxygenic phototrophy, carbon fixation via the rTCA pathway, and iron oxidation all significantly postdating the rise of oxygen ~2.3 billion years ago. The Chlorobi therefore could not have fueled the Archean biosphere, but instead represent a relatively young radiation of organisms which likely acquired the capacity for anoxygenic photosynthesis and other traits via horizontal gene transfer sometime after the evolution of oxygenic Cyanobacteria.


Assuntos
Chlorobi , Ciclo do Carbono , Chlorobi/genética , Ferro/metabolismo , Oxigênio/metabolismo , Fotossíntese , Processos Fototróficos , Filogenia
11.
Microbiol Spectr ; 10(3): e0146521, 2022 06 29.
Artigo em Inglês | MEDLINE | ID: mdl-35575591

RESUMO

Alkaline hot springs in Yellowstone National Park (YNP) provide a framework to study the relationship between photoautotrophs and temperature. Previous work has focused on studying how cyanobacteria (oxygenic phototrophs) vary with temperature, sulfide, and pH, but many questions remain regarding the ecophysiology of anoxygenic photosynthesis due to the taxonomic and metabolic diversity of these taxa. To this end, we examined the distribution of genes involved in phototrophy, carbon fixation, and nitrogen fixation in eight alkaline (pH 7.3-9.4) hot spring sites near the upper temperature limit of photosynthesis (71ºC) in YNP using metagenome sequencing. Based on genes encoding key reaction center proteins, geographic isolation plays a larger role than temperature in selecting for distinct phototrophic Chloroflexi, while genes typically associated with autotrophy in anoxygenic phototrophs, did not have distinct distributions with temperature. Additionally, we recovered Calvin cycle gene variants associated with Chloroflexi, an alternative carbon fixation pathway in anoxygenic photoautotrophs. Lastly, we recovered several abundant nitrogen fixation gene sequences associated with Roseiflexus, providing further evidence that genes involved in nitrogen fixation in Chloroflexi are more common than previously assumed. Together, our results add to the body of work on the distribution and functional potential of phototrophic bacteria in Yellowstone National Park hot springs and support the hypothesis that a combination of abiotic and biotic factors impact the distribution of phototrophic bacteria in hot springs. Future studies of isolates and metagenome assembled genomes (MAGs) from these data and others will further our understanding of the ecology and evolution of hot spring anoxygenic phototrophs. IMPORTANCE Photosynthetic bacteria in hot springs are of great importance to both microbial evolution and ecology. While a large body of work has focused on oxygenic photosynthesis in cyanobacteria in Mushroom and Octopus Springs in Yellowstone National Park, many questions remain regarding the metabolic potential and ecology of hot spring anoxygenic phototrophs. Anoxygenic phototrophs are metabolically and taxonomically diverse, and further investigations into their physiology will lead to a deeper understanding of microbial evolution and ecology of these taxa. Here, we have quantified the distribution of key genes involved in carbon and nitrogen metabolism in both oxygenic and anoxygenic phototrophs. Our results suggest that temperature >68ºC selects for distinct groups of cyanobacteria and that carbon fixation pathways associated with these taxa are likely subject to the same selective pressure. Additionally, our data suggest that phototrophic Chloroflexi genes and carbon fixation genes are largely influenced by local conditions as evidenced by our gene variant analysis. Lastly, we recovered several genes associated with potentially novel phototrophic Chloroflexi. Together, our results add to the body of work on hot springs in Yellowstone National Park and set the stage for future work on metagenome assembled genomes.


Assuntos
Chloroflexi , Cianobactérias , Fontes Termais , Chloroflexi/genética , Chloroflexi/metabolismo , Cianobactérias/genética , Cianobactérias/metabolismo , Fontes Termais/microbiologia , Processos Fototróficos , Filogenia , Temperatura
12.
J Proteomics ; 260: 104569, 2022 05 30.
Artigo em Inglês | MEDLINE | ID: mdl-35354086

RESUMO

Anoxygenic phototrophic bacteria display phenomenal metabolic plasticity leading to distinct phenotypes. Extracellular elevated glucose levels limit photosynthesis in photosynthetic organisms; diversely, cause oxidative stress with ROS generation and "diabetic" like situation in non-photosynthetic organisms. In this study, longer incubations of externally provided glucose (22 mM) inhibited photosynthetic machinery in a phototrophic bacterium, Rubrivivax benzoatilyticus. Data analysis at three time points- exponential, early and late stationary phase, uncovered dynamic protein and metabolite abundance implying metabolic rewiring led non-cultivable state in response to glucose. Protein dynamics datum suggested that proteins related to primary metabolism down-regulated prior to those of secondary metabolism. Numerous proteins for metabolism and energy generation were highly expressed during exponential phase whereas those for membrane transport/translocation and DNA repair accumulated at early and late stationary phase respectively, suggesting a programmed knock-off of phototrophic growth mode and a switch to non-cultivable state. Overall, the omics analyses explicated the metabolic adjustment associated with glucose grown cells of R. benzoatilyticus. Further, our investigation unravelled creation of oxidative stress suggesting physiological stress (oxygen limitation) might be a key player leading to a non-cultivable state in this phototrophic organism. The study, emphasizing microbial glucose intolerance, unlocks the doorway to perceive microorganisms with new perspective. SIGNIFICANCE: Anoxygenic photosynthetic bacteria (APB), thriving under diverse habitat, exhibits magnificent metabolic flexibility. Generally, phototrophy is the preferred growth mode and energy generating route for APB. But, our analyses implicated that the glucose, under phototrophic growth conditions, triggered photobleaching in an APB member, Rubrivivax benzoatilyticus. However, retention of growth along with pigmentation under chemotrophic growth mode supports that glucose gradually knocked off the phototrophic growth mode of R. benzoatilyticus and switched to an alternate energy driving route or less energy demanding non-cultivabile state. Thus, the change in lifestyle i.e. photoheterotrophic growth instead of chemotrophic perhaps, might be the prime culprit and key player in inducing the said state of non-cultivability, akin to diabetes. The study, shedding light on the plausible regulation of cultivability, unveils the programmed regulated switching between different growth modes of the organism and illuminates the importance of glucose intolerance by microorganisms. Through this investigation, we appeal that the studies on 'glucose intolerance in microorganisms' also need due attention that will perhaps change our outlook to perceive micro-organisms in relation to their physiological life style.


Assuntos
Burkholderiales , Metaboloma , Processos Fototróficos , Burkholderiales/metabolismo , Glucose/metabolismo , Fotossíntese
13.
Proc Natl Acad Sci U S A ; 118(45)2021 11 09.
Artigo em Inglês | MEDLINE | ID: mdl-34732568

RESUMO

Numerous diverse microorganisms reside in the cold desert soils of continental Antarctica, though we lack a holistic understanding of the metabolic processes that sustain them. Here, we profile the composition, capabilities, and activities of the microbial communities in 16 physicochemically diverse mountainous and glacial soils. We assembled 451 metagenome-assembled genomes from 18 microbial phyla and inferred through Bayesian divergence analysis that the dominant lineages present are likely native to Antarctica. In support of earlier findings, metagenomic analysis revealed that the most abundant and prevalent microorganisms are metabolically versatile aerobes that use atmospheric hydrogen to support aerobic respiration and sometimes carbon fixation. Surprisingly, however, hydrogen oxidation in this region was catalyzed primarily by a phylogenetically and structurally distinct enzyme, the group 1l [NiFe]-hydrogenase, encoded by nine bacterial phyla. Through gas chromatography, we provide evidence that both Antarctic soil communities and an axenic Bacteroidota isolate (Hymenobacter roseosalivarius) oxidize atmospheric hydrogen using this enzyme. Based on ex situ rates at environmentally representative temperatures, hydrogen oxidation is theoretically sufficient for soil communities to meet energy requirements and, through metabolic water production, sustain hydration. Diverse carbon monoxide oxidizers and abundant methanotrophs were also active in the soils. We also recovered genomes of microorganisms capable of oxidizing edaphic inorganic nitrogen, sulfur, and iron compounds and harvesting solar energy via microbial rhodopsins and conventional photosystems. Obligately symbiotic bacteria, including Patescibacteria, Chlamydiae, and predatory Bdellovibrionota, were also present. We conclude that microbial diversity in Antarctic soils reflects the coexistence of metabolically flexible mixotrophs with metabolically constrained specialists.


Assuntos
Clima Desértico , Gases/metabolismo , Camada de Gelo/microbiologia , Microbiota , Microbiologia do Solo , Regiões Antárticas , Processos Autotróficos , Biodiversidade , Hidrogenase/metabolismo , Metagenoma , Oxirredução , Processos Fototróficos
14.
Microbiol Spectr ; 9(3): e0069421, 2021 12 22.
Artigo em Inglês | MEDLINE | ID: mdl-34787442

RESUMO

Viruses exert diverse ecosystem impacts by controlling their host community through lytic predator-prey dynamics. However, the mechanisms by which lysogenic viruses influence their host-microbial community are less clear. In hot springs, lysogeny is considered an active lifestyle, yet it has not been systematically studied in all habitats, with phototrophic microbial mats (PMMs) being particularly not studied. We carried out viral metagenomics following in situ mitomycin C induction experiments in PMMs from Porcelana hot spring (Northern Patagonia, Chile). The compositional changes of viral communities at two different sites were analyzed at the genomic and gene levels. Furthermore, the presence of integrated prophage sequences in environmental metagenome-assembled genomes from published Porcelana PMM metagenomes was analyzed. Our results suggest that virus-specific replicative cycles (lytic and lysogenic) were associated with specific host taxa with different metabolic capacities. One of the most abundant lytic viral groups corresponded to cyanophages, which would infect the cyanobacteria Fischerella, the most active and dominant primary producer in thermophilic PMMs. Likewise, lysogenic viruses were related exclusively to chemoheterotrophic bacteria from the phyla Proteobacteria, Firmicutes, and Actinobacteria. These temperate viruses possess accessory genes to sense or control stress-related processes in their hosts, such as sporulation and biofilm formation. Taken together, these observations suggest a nexus between the ecological role of the host (metabolism) and the type of viral lifestyle in thermophilic PMMs. This has direct implications in viral ecology, where the lysogenic-lytic switch is determined by nutrient abundance and microbial density but also by the metabolism type that prevails in the host community. IMPORTANCE Hot springs harbor microbial communities dominated by a limited variety of microorganisms and, as such, have become a model for studying community ecology and understanding how biotic and abiotic interactions shape their structure. Viruses in hot springs are shown to be ubiquitous, numerous, and active components of these communities. However, lytic and lysogenic viral communities of thermophilic phototrophic microbial mats (PMMs) remain largely unexplored. In this work, we use the power of viral metagenomics to reveal changes in the viral community following a mitomycin C induction experiment in PMMs. The importance of our research is that it will improve our understanding of viral lifestyles in PMMs via exploring the differences in the composition of natural and induced viral communities at the genome and gene levels. This novel information will contribute to deciphering which biotic and abiotic factors may control the transitions between lytic and lysogenic cycles in these extreme environments.


Assuntos
Bactérias/virologia , Fontes Termais/virologia , Lisogenia , Vírus/genética , Bactérias/classificação , Bactérias/genética , Bactérias/efeitos da radiação , Biodiversidade , Variação Genética , Metagenoma , Processos Fototróficos , Filogenia , Fenômenos Fisiológicos Virais , Vírus/classificação , Vírus/isolamento & purificação
15.
World J Microbiol Biotechnol ; 37(12): 215, 2021 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-34762205

RESUMO

The demand for natural antioxidants to be used in food industry is increasing, as synthetic antioxidants are toxic and have high production costs. Specifically, food processing and preservation require antioxidants resistant to thermal sterilization processes. In this study, twenty-five strains among microalgae and cyanobacteria were screened as antioxidants producers. The species Enallax sp., Synechococcus bigranulatus and Galdieria sulphuraria showed the highest content of chlorophyll a and total carotenoids. In vitro stability and antioxidant activity of the ethanolic extracts were performed. The results revealed that pigments present in the extracts, obtained from the previously mentioned species, were stable at room temperature and exhibited in vitro free radical scavenging potential with IC50 values of 0.099 ± 0.001, 0.048 ± 0.001 and 0.13 ± 0.02 mg mL-1, respectively. Biocompatibility assay showed that the extracts were not toxic on immortalized cell lines. The antioxidant activity was also tested on a cell-based model by measuring intracellular ROS levels after sodium arsenite treatment. Noteworthy, extracts were able to exert the same protective effect, before and after the pasteurization process. Results clearly indicate the feasibility of obtaining biologically active and thermostable antioxidants from microalgae. Green solvents can be used to obtain thermo-resistant antioxidants from cyanobacteria and microalgae which can be used in the food industry. Thus, the substitution of synthetic pigments with natural ones is now practicable.


Assuntos
Antioxidantes/química , Cianobactérias/química , Microalgas/química , Antioxidantes/isolamento & purificação , Antioxidantes/metabolismo , Processos Autotróficos , Clorofila A/metabolismo , Cianobactérias/metabolismo , Cianobactérias/efeitos da radiação , Temperatura Alta , Microalgas/metabolismo , Microalgas/efeitos da radiação , Processos Fototróficos , Espécies Reativas de Oxigênio/metabolismo
17.
Astrobiology ; 21(10): 1237-1249, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34569810

RESUMO

We show that solar irradiances calculated across Venus' clouds support the potential for Earth-like phototrophy and that treatment of Venus' aerosols containing neutralized sulfuric acid favor a habitable zone. The phototrophic potential of Venus' atmosphere was assessed by calculating irradiances (200-2000 nm, 15° solar zenith angle, local noon) using a radiative transfer model that accounted for absorption and scattering by the major and minor atmospheric constituents. Comparisons to Earth's surface (46 W m-2, 280-400 nm) suggest that Venus' middle and lower clouds receive ∼87% less normalized UV flux (6-7 W m-2) across 200-400 nm, yet similar normalized photon flux densities (∼4400-6200 µmol m-2 s-1) across 350-1200 nm. Further, Venus' signature phototrophic windows and subwindows overlap with the absorption profiles of several photosynthetic pigments, especially bacteriochlorophyll b from intact cells and phycocyanin. Therefore, Venus' light, with limited UV flux in the middle and lower clouds, is likely quite favorable for phototrophy. We additionally present interpretations to refractive index and radio occultation measures for Venus' aerosols that suggest the presence of lower sulfuric abundances and/or neutralized forms of sulfuric acid, such as ammonium bisulfate. Under these considerations, the aerosols in Venus' middle clouds could harbor water activities (≥0.6) and buffered acidities (Hammett acidity factor, H0 -0.1 to -1.5) that lie within the limits of acidic cultivation (≥H0 -0.4) and are tantalizingly close to the limits of oxygenic photosynthesis (≥H0 0.1). Together, these photophysical and chemical considerations support a potential for phototrophy in Venus' clouds.


Assuntos
Vênus , Atmosfera , Planeta Terra , Processos Fototróficos , Água
18.
Proc Natl Acad Sci U S A ; 118(38)2021 09 21.
Artigo em Inglês | MEDLINE | ID: mdl-34521754

RESUMO

Eukaryote-eukaryote endosymbiosis was responsible for the spread of chloroplast (plastid) organelles. Stability is required for the metabolic and genetic integration that drives the establishment of new organelles, yet the mechanisms that act to stabilize emergent endosymbioses-between two fundamentally selfish biological organisms-are unclear. Theory suggests that enforcement mechanisms, which punish misbehavior, may act to stabilize such interactions by resolving conflict. However, how such mechanisms can emerge in a facultative endosymbiosis has yet to be explored. Here, we propose that endosymbiont-host RNA-RNA interactions, arising from digestion of the endosymbiont population, can result in a cost to host growth for breakdown of the endosymbiosis. Using the model facultative endosymbiosis between Paramecium bursaria and Chlorella spp., we demonstrate that this mechanism is dependent on the host RNA-interference (RNAi) system. We reveal through small RNA (sRNA) sequencing that endosymbiont-derived messenger RNA (mRNA) released upon endosymbiont digestion can be processed by the host RNAi system into 23-nt sRNA. We predict multiple regions of shared sequence identity between endosymbiont and host mRNA, and demonstrate through delivery of synthetic endosymbiont sRNA that exposure to these regions can knock down expression of complementary host genes, resulting in a cost to host growth. This process of host gene knockdown in response to endosymbiont-derived RNA processing by host RNAi factors, which we term "RNAi collisions," represents a mechanism that can promote stability in a facultative eukaryote-eukaryote endosymbiosis. Specifically, by imposing a cost for breakdown of the endosymbiosis, endosymbiont-host RNA-RNA interactions may drive maintenance of the symbiosis across fluctuating ecological conditions.


Assuntos
Processos Fototróficos/genética , RNA/genética , Simbiose/genética , Chlorella/genética , Cloroplastos/genética , Eucariotos/genética , Paramecium/genética , Plastídeos/genética , Interferência de RNA/fisiologia
19.
Microbes Environ ; 36(3)2021.
Artigo em Inglês | MEDLINE | ID: mdl-34470945

RESUMO

Roseilinea is a novel lineage of Chloroflexota known only from incomplete metagenome-assembled genomes (MAGs) and preliminary enrichments. Roseilinea is notable for appearing capable of anoxygenic photoheterotrophy despite being only distantly related to well-known phototrophs in the Chloroflexia class such as Chloroflexus and Roseiflexus. Here, we present a high-quality MAG of a member of Roseilinea, improving our understanding of the metabolic capacity and phylogeny of this genus, and resolving the multiple instances of horizontal gene transfer that have led to its metabolic potential. These data allow us to propose a candidate family for these organisms, Roseilineaceae, within the Anaerolineae class.


Assuntos
Chloroflexi/genética , Chloroflexi/metabolismo , Genoma Bacteriano , Sequência de Bases , Chloroflexi/classificação , Chloroflexi/isolamento & purificação , Transferência Genética Horizontal , Dados de Sequência Molecular , Processos Fototróficos , Filogenia
20.
mSphere ; 6(4): e0052521, 2021 08 25.
Artigo em Inglês | MEDLINE | ID: mdl-34406852

RESUMO

Microbial proton-pumping rhodopsins are considered the simplest strategy among phototrophs to conserve energy from light. Proteorhodopsins are the most studied rhodopsins thus far because of their ubiquitous presence in the ocean, except in Antarctica, where they remain understudied. We analyzed proteorhodopsin abundance and transcriptional activity in the Western Antarctic coastal seawaters. Combining quantitative PCR (qPCR) and metagenomics, the relative abundance of proteorhodopsin-bearing bacteria accounted on average for 17, 3.5, and 29.7% of the bacterial community in Chile Bay (South Shetland Islands) during 2014, 2016, and 2017 summer-autumn, respectively. The abundance of proteorhodopsin-bearing bacteria changed in relation to environmental conditions such as chlorophyll a and temperature. Alphaproteobacteria, Gammaproteobacteria, and Flavobacteriia were the main bacteria that transcribed the proteorhodopsin gene during day and night. Although green light-absorbing proteorhodopsin genes were more abundant than blue-absorbing ones, the latter were transcribed more intensely, resulting in >50% of the proteorhodopsin transcripts during the day and night. Flavobacteriia were the most abundant proteorhodopsin-bearing bacteria in the metagenomes; however, Alphaproteobacteria and Gammaproteobacteria were more represented in the metatranscriptomes, with qPCR quantification suggesting the dominance of the active SAR11 clade. Our results show that proteorhodopsin-bearing bacteria are prevalent in Antarctic coastal waters in late austral summer and early autumn, and their ecological relevance needs to be elucidated to better understand how sunlight energy is used in this marine ecosystem. IMPORTANCE Proteorhodopsin-bearing microorganisms in the Southern Ocean have been overlooked since their discovery in 2000. The present study identify taxonomy and quantify the relative abundance of proteorhodopsin-bearing bacteria and proteorhodopsin gene transcription in the West Antarctic Peninsula's coastal waters. This information is crucial to understand better how sunlight enters this marine environment through alternative ways unrelated to chlorophyll-based strategies. The relative abundance of proteorhodopsin-bearing bacteria seems to be related to environmental parameters (e.g., chlorophyll a, temperature) that change yearly at the coastal water of the West Antarctic Peninsula during the austral late summers and early autumns. Proteorhodopsin-bearing bacteria from Antarctic coastal waters are potentially able to exploit both the green and blue spectrum of sunlight and are a prevalent group during the summer in this polar environment.


Assuntos
Metagenômica/métodos , Microbiota/genética , Processos Fototróficos , Rodopsinas Microbianas/genética , Água do Mar/microbiologia , Alphaproteobacteria/química , Alphaproteobacteria/classificação , Alphaproteobacteria/genética , Regiões Antárticas , Ecossistema , Flavobacteriaceae/química , Flavobacteriaceae/classificação , Flavobacteriaceae/genética , Filogenia , Rodopsina/metabolismo , Rodopsinas Microbianas/análise
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