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1.
ISME J ; 2020 Nov 23.
Artigo em Inglês | MEDLINE | ID: mdl-33230267

RESUMO

Bottom-up selection has an important role in microbial community assembly but is unable to account for all observed variance. Other processes like top-down selection (e.g., predation) may be partially responsible for the unexplained variance. However, top-down processes and their interaction with bottom-up selective pressures often remain unexplored. We utilised an in situ marine biofilm model system to test the effects of bottom-up (i.e., substrate properties) and top-down (i.e., large predator exclusion via 100 µm mesh) selective pressures on community assembly over time (56 days). Prokaryotic and eukaryotic community compositions were monitored using 16 S and 18 S rRNA gene amplicon sequencing. Higher compositional variance was explained by growth substrate in early successional stages, but as biofilms mature, top-down predation becomes progressively more important. Wooden substrates promoted heterotrophic growth, whereas inert substrates' (i.e., plastic, glass, tile) lack of degradable material selected for autotrophs. Early wood communities contained more mixotrophs and heterotrophs (e.g., the total abundance of Proteobacteria and Euglenozoa was 34% and 41% greater within wood compared to inert substrates). Inert substrates instead showed twice the autotrophic abundance (e.g., cyanobacteria and ochrophyta made up 37% and 10% more of the total abundance within inert substrates than in wood). Late native (non-enclosed) communities were mostly dominated by autotrophs across all substrates, whereas high heterotrophic abundance characterised enclosed communities. Late communities were primarily under top-down control, where large predators successively pruned heterotrophs. Integrating a top-down control increased explainable variance by 7-52%, leading to increased understanding of the underlying ecological processes guiding multitrophic community assembly and successional dynamics.

2.
Oecologia ; 193(3): 583-591, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32556588

RESUMO

Benthic primary producers in coastal ecosystems provide important habitat for marine organisms through the provision of complex 3D habitat. Primary producers produce organic matter, while simultaneously producing reactive oxygen species, including hydrogen peroxide (H2O2), a driver of oxidative stress. Through their high biomass, productivity and effect on local hydrodynamics, benthic primary producers can potentially increase H2O2 concentrations surrounding the biogenic structures they form. The aim of this study was to identify the potential role of H2O2 produced by benthic primary producers as an external stressor in coastal ecosystems. This was achieved by measuring H2O2 concentrations within sea lettuce blooms (Ulva sp.), giant kelp forests (Macrocystis pyrifera), and seagrass meadows (Zostera muelleri); quantifying H2O2 production rates of these species; and testing heterotrophic bacterial response to relevant H2O2 concentrations. Ulva sp. produced five times more H2O2 than other species. At in situ concentrations, H2O2 inhibited bacterial production and carbon flow through the microbial loop by 75%. This study reveals H2O2 as an additional stressor in bloom-forming Ulva sp. with higher H2O2 production compared to the ecosystem engineers M. pyrifera and Z. muelleri. H2O2 production by benthic primary producers can affect carbon flow through the microbial loop, with the potential to propagate a stress signal up the food web.


Assuntos
Ecossistema , Macrocystis , Biomassa , Cadeia Alimentar , Peróxido de Hidrogênio
3.
Sci Adv ; 6(16): eaaz4354, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32494615

RESUMO

Heterotrophic prokaryotes express extracellular hydrolytic enzymes to cleave large organic molecules before taking up the hydrolyzed products. According to foraging theory, extracellular enzymes should be cell associated in dilute systems such as deep sea habitats, but secreted into the surrounding medium in diffusion-limited systems. However, extracellular enzymes in the deep sea are found mainly dissolved in ambient water rather than cell associated. In order to resolve this paradox, we conducted a global survey of peptidases and carbohydrate-active enzymes (CAZymes), two key enzyme groups initiating organic matter assimilation, in an integrated metagenomics, metatranscriptomics, and metaproteomics approach. The abundance, percentage, and diversity of genes encoding secretory processes, i.e., dissolved enzymes, consistently increased from epipelagic to bathypelagic waters, indicating that organic matter cleavage, and hence prokaryotic metabolism, is mediated mainly by particle-associated prokaryotes releasing their extracellular enzymes into diffusion-limited particles in the bathypelagic realm.

4.
Environ Microbiol ; 22(5): 1930-1943, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32249543

RESUMO

Compared to higher latitudes, tropical heterotrophic bacteria may be less responsive to warming because of strong bottom-up control. In order to separate both drivers, we determined the growth responses of bacterial physiological groups to temperature after adding dissolved organic matter (DOM) from mangroves, seagrasses and glucose to natural seawater from the Great Barrier Reef. Low (LNA) and high (HNA) nucleic acid content, membrane-intact (Live) and membrane-damaged (Dead) plus actively respiring (CTC+) cells were monitored for 4 days. Specific growth rates of the whole community were significantly higher (1.9 day-1 ) in the mangrove treatment relative to the rest (0.2-0.4 day-1 ) at in situ temperature and their temperature dependence, estimated as activation energy, was also consistently higher. Strong bottom-up control was suggested in the other treatments. Cell size depended more on DOM than temperature. Mangrove DOM resulted in significantly higher contributions of Live, HNA and CTC+ cells to total abundance, while the seagrass leachate reduced Live cells below 50%. Warming significantly decreased Live and CTC+ cells contributions in most treatments. Our results suggest that only in the presence of highly labile compounds, such as mangroves DOM, can we anticipate increases in heterotrophic bacteria biomass in response to warming in tropical regions.

5.
Sci Rep ; 10(1): 3274, 2020 02 24.
Artigo em Inglês | MEDLINE | ID: mdl-32094391

RESUMO

Increased atmospheric CO2 is driving ocean acidification (OA), and potential changes in marine ecosystems. Research shows that both planktonic and benthic communities are affected, but how these changes are linked remains unresolved. Here we show experimentally that decreasing seawater pH (from pH 8.1 to 7.8 and 7.4) leads to reduced biofilm formation and lower primary producer biomass within biofilms. These changes occurred concurrently with a re-arrangement of the biofilm microbial communities. Changes suggest a potential shift from autotrophic to heterotrophic dominated biofilms in response to reduced pH. In a complimentary experiment, biofilms reared under reduced pH resulted in altered larval settlement for a model species (Galeolaria hystrix). These findings show that there is a potential cascade of impacts arising from OA effects on biofilms that may drive important community shifts through altered settlement patterns of benthic species.

6.
Front Microbiol ; 10: 2807, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31866976

RESUMO

Global change impacts on marine biogeochemistry will be partly mediated by heterotrophic bacteria. Besides ocean warming, future environmental changes have been suggested to affect the quantity and quality of organic matter available for bacterial growth. However, it is yet to be determined in what way warming and changing substrate conditions will impact marine heterotrophic bacteria activity. Using short-term (4 days) experiments conducted at three temperatures (-3°C, in situ, +3°C) we assessed the temperature dependence of bacterial cycling of marine surface water used as a control and three different dissolved organic carbon (DOC) substrates (glucose, seagrass, and mangrove) in tropical coastal waters of the Great Barrier Reef, Australia. Our study shows that DOC source had the largest effect on the measured bacterial response, but this response was amplified by increasing temperature. We specifically demonstrate that (1) extracellular enzymatic activity and DOC consumption increased with warming, (2) this enhanced DOC consumption did not result in increased biomass production, since the increases in respiration were larger than for bacterial growth with warming, and (3) different DOC bioavailability affected the magnitude of the microbial community response to warming. We suggest that in coastal tropical waters, the magnitude of heterotrophic bacterial productivity and enzyme activity response to warming will depend partly on the DOC source bioavailability.

7.
Medicina (B Aires) ; 79 Suppl 3: 10-14, 2019.
Artigo em Espanhol | MEDLINE | ID: mdl-31603836

RESUMO

Preterm birth is one of the main country health indicators. It is associated with high mortality and significant morbidity in preterm newborns with cerebral palsy and potential long-term neurodevelopmental disabilities like cognitive and learning problems. The main lesions could be: a) white matter injuries, generally associated with cortical and other regions of grey matter neuronal-axonal disturbances; b) intracranial hemorrhage that includes germinal matrix, intraventricular and parenchymal, c) cerebellum injuries. The white matter lesions include cystic and non-cystic (with microscopic focal necrosis) periventricular leukomalacia and non-necrotic diffuse white matter injury. Multiple etiologic factors are associated with these injuries. Anatomical and physiological characteristics of periventricular vascular structures predispose white matter to cerebral ischemia and, interacting with infection/inflammation factors, activate microglia, generating oxidative stress (mediated by free oxygen and nitrogen radicals), pro-inflammatory cytokine and glutamate toxicity, energetic failure and vascular integrity disturbances. All these factors lead to a particular vulnerability of pre-oligodendrocytes that will affect myelination. Hypoxia-ischemia also may produce selective neuronal necrosis in different cerebral regions. Germinal matrix is a highly vascularized zone beneath ependymal or periventricular region that constitutes a capillary bed with a particular structural fragility that predispose it to hemorrhage.


Assuntos
Lesões Encefálicas/etiologia , Isquemia Encefálica/etiologia , Paralisia Cerebral/etiologia , Hipóxia-Isquemia Encefálica/etiologia , Recém-Nascido Prematuro , Leucomalácia Periventricular/etiologia , Lesões Encefálicas/diagnóstico por imagem , Lesões Encefálicas/mortalidade , Isquemia Encefálica/diagnóstico por imagem , Isquemia Encefálica/mortalidade , Paralisia Cerebral/mortalidade , Humanos , Hipóxia-Isquemia Encefálica/diagnóstico por imagem , Hipóxia-Isquemia Encefálica/mortalidade , Recém-Nascido , Leucomalácia Periventricular/diagnóstico por imagem , Leucomalácia Periventricular/mortalidade , Substância Branca/patologia
8.
Medicina (B.Aires) ; 79(supl.3): 10-14, set. 2019. ilus
Artigo em Espanhol | LILACS-Express | LILACS | ID: biblio-1040542

RESUMO

Los nacimientos prematuros son uno de los principales indicadores de salud de un país. Están asociados a una alta mortalidad e importante morbilidad en niños con parálisis cerebral y otros trastornos del neurodesarrollo, incluyendo problemas cognitivos y del aprendizaje. Los principales tipos de lesión encefálica en los recién nacidos prematuros son: a) las lesiones de la sustancia blanca, generalmente asociadas a alteraciones neuronales y axonales en la corteza cerebral y otras zonas de sustancia gris; b) hemorragias intracraneanas que incluyen las de la matriz germinal, intraventriculares e intraparenquimatosas y c) del cerebelo. Las lesiones de sustancia blanca incluyen la leucomalacia periventricular quística, no quística (con focos de necrosis microscópicos) y lesiones difusas de sustancia blanca, no necróticas. Estas lesiones tienen múltiples factores etiológicos. Las características anatómicas y fisiológicas de las estructuras vasculares periventriculares predisponen a la sustancia blanca a ser muy vulnerable a las situaciones de isquemia cerebral y, en interacción con factores infecciosos/inflamatorios, activan a las microglías generando estrés oxidativo (por liberación de radicales libres del oxígeno y del nitrógeno), liberación de citoquinas proinflamatorias, liberación de glutamato, fallo energético y alteración de la integridad vascular. Todo lo anteriormente mencionado genera una particular vulnerabilidad de los pre-oligodendrocitos que termina alterando la mielinización. La hipoxia-isquemia también puede producir necrosis neuronal selectiva en diferentes regiones encefálicas. La matriz germinal es un área altamente vascularizada en la región subependimaria periventricular con una estructura capilar muy frágil que la predispone a las hemorragias.


Preterm birth is one of the main country health indicators. It is associated with high mortality and significant morbidity in preterm newborns with cerebral palsy and potential long-term neurodevelopmental disabilities like cognitive and learning problems. The main lesions could be: a) white matter injuries, generally associated with cortical and other regions of grey matter neuronal-axonal disturbances; b) intracranial hemorrhage that includes germinal matrix, intraventricular and parenchymal, c) cerebellum injuries. The white matter lesions include cystic and non-cystic (with microscopic focal necrosis) periventricular leukomalacia and non-necrotic diffuse white matter injury. Multiple etiologic factors are associated with these injuries. Anatomical and physiological characteristics of periventricular vascular structures predispose white matter to cerebral ischemia and, interacting with infection/inflammation factors, activate microglia, generating oxidative stress (mediated by free oxygen and nitrogen radicals), pro-inflammatory cytokine and glutamate toxicity, energetic failure and vascular integrity disturbances. All these factors lead to a particular vulnerability of pre-oligodendrocytes that will affect myelination. Hypoxia-ischemia also may produce selective neuronal necrosis in different cerebral regions. Germinal matrix is a highly vascularized zone beneath ependymal or periventricular region that constitutes a capillary bed with a particular structural fragility that predispose it to hemorrhage.

9.
Sci Total Environ ; 693: 133507, 2019 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-31377366

RESUMO

Systems with strong horizontal and vertical gradients, such as fjords, are useful models for studying environmental forcing. Here we examine microbial (prokaryotic and eukaryotic) community changes associated with the surface low salinity layer (LSL) and underlying seawater in multiple fjords in Fiordland National Park (New Zealand). High rainfall (1200-8000 mm annually) and linked runoff from native forested catchments results in surface LSLs with high tannin concentrations within each fjord. These gradients are expected to drive changes in microbial communities. We used amplicon sequencing (16S and 18S) to assess the impact of these gradients on microbial communities and identified depth linked changes in diversity and community structure. With increasing depth, we observed significant increases in Proteobacteria (15%) and SAR (37%), decreases in Opisthokonta (35%), and transiently increased Bacteroidetes (3% increase from 0 to 40 m, decreasing by 8% at 200 m). Community structure differences were observed along a transect from the head to the mouth, specifically 25% mean relative abundance decreases in Opisthokonta and Bacteroidetes, and increases in SAR (25%) and Proteobacteria (>5%) at the surface, indicating changes based on distance from the ocean. This provides the first in-depth view into the ecological drivers of microbial communities within New Zealand fjords.


Assuntos
Microbiota/fisiologia , Fitoplâncton/fisiologia , Água do Mar/química , Archaea/fisiologia , Fenômenos Fisiológicos Bacterianos , Estuários , Eucariotos , Nova Zelândia , Salinidade
10.
Trends Ecol Evol ; 34(11): 1022-1033, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31350054

RESUMO

Global environmental changes are challenging the structure and functioning of ecosystems. However, a mechanistic understanding of how global environmental changes will affect ecosystems is still lacking. The complex and interacting biological and physical processes spanning vast temporal and spatial scales that constitute an ecosystem make this a formidable problem. A unifying framework based on ecological theory, that considers fundamental and realized niches, combined with metabolic, evolutionary, and climate change studies, is needed to provide the mechanistic understanding required to evaluate and forecast the future of marine communities, ecosystems, and their services.


Assuntos
Mudança Climática , Ecossistema , Ecologia
11.
Microbes Environ ; 34(1): 83-88, 2019 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-30799317

RESUMO

Marine microbes play a central role in driving biogeochemical cycles. Microbial extracellular enzymatic activities (EEA) are the 'gatekeeper' of the marine carbon cycle, and these enzymes may be found attached to cells or dissolved (cell-free). Recent studies indicated that the proportion of dissolved enzymatic activity is generally similar to (if not higher than) cell-attached activity. Thus, it is critical to understand the sources and sinks of cell-free EEA in the ocean. We herein empirically tested whether bacterial stress and mortality (induced by mitomycin C) are a source of the cell-free EEA of alkaline phosphatase (APase), beta-glucosidase (BGase), and leucine aminopeptidase (LAPase). We found that bacterial stress and mortality caused relative increases in the proportion of dissolved relative to total EEA of up to 10.5% for APase, 13.5% for BGase, and 7.3% for LAPase. These relative increases in dissolved EEA corresponded to absolute increases in the cell-free pool of 4.8, 7.2, and 3.8% for APase, BGase and LAPase, respectively. Collectively, our results contribute relevant information on the origin of free dissolved extracellular enzymes in marine waters, indicating that bacterial stress and mortality are a source of cell-free enzymatic activity and suggesting a potential link between microbial interactions and the degradation of organic matter via the release of cell-free enzymes.


Assuntos
Fenômenos Fisiológicos Bacterianos , Espaço Extracelular/enzimologia , Água do Mar/microbiologia , Bactérias/enzimologia , Bactérias/crescimento & desenvolvimento , Proteínas de Bactérias/análise , Proteínas de Bactérias/química , Ecossistema , Viabilidade Microbiana/efeitos dos fármacos , Mitomicina/farmacologia , Água do Mar/química , Estresse Fisiológico/efeitos dos fármacos
12.
Sci Total Environ ; 660: 690-696, 2019 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-30743954

RESUMO

Extracellular enzymatic activity (EEA) is performed by cell-associated and cell-free (i.e., "dissolved") enzymes. This cell-free fraction is operationally defined as passing through a 0.22 µm filter. The contribution of cell-free to total EEA is comparable to the cell-associated counterpart, so it is critical to understand what controls the relative importance of cell-free versus cell-associated EEA. However, attempts to tease apart the contribution of EEAs in the so-called dissolved fraction (<0.22 µm) in general, and of the nanoparticle size fraction (0.020-0.20 µm) in particular, to the total EEA pool are lacking. Here we performed experiments with Northern and Southern Hemisphere coastal waters to characterize the potential contribution of that nanoparticle fraction to the total EEA fraction of alkaline phosphatase, beta-glucosidase and leucine aminopeptidase. We found a significant contribution (in both hemispheres) of the nanoparticle fraction to the total EEA pool (up to 53%) that differed depending on the enzyme type and location. Collectively, our results indicate that a significant fraction of the so-called "dissolved EEA" is not really dissolved but associated to nanoparticles, colloidal nanogels and/or viruses. Thus, the total marine EEA pool can actually be divided into a cell-associated, undissolved-cell-free (associated to nano-particle of different origins such as viruses and nanogels) and a dissolved-cell-free pools. Our results also imply that the dissolved EEA pool is more complex than thus far anticipated. Future research will be now needed to further characterize the factors controlling the relative importance of these different pools of EEA, which are key in the recycling of organic matter in the ocean.


Assuntos
Monitoramento Ambiental , Água do Mar/microbiologia , Microbiologia da Água , Fosfatase Alcalina/análise , Bactérias , Leucil Aminopeptidase/análise , Oceanos e Mares , Vírus , beta-Glucosidase/análise
13.
Environ Microbiol Rep ; 10(2): 184-189, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29377623

RESUMO

Ecotones are regarded as diversity hotspots in terrestrial systems, but it is unknown if this 'ecotone effect' occurs in the marine environment. Oceanic fronts are widespread mesoscale features, present in the boundary between different water masses, and are arguably the best potential examples of ecotones in the ocean. Here we performed the first seasonal study along an oceanic front, combining 16S rRNA gene sequencing coupled with a high spatial resolution analysis of the physical properties of the water masses. Using the Subtropical Frontal Zone off New Zealand we demonstrate that fronts delimit shifts in bacterioplankton community composition between water masses, but that the strength of this effect is seasonally dependent. While creating a transition zone where physicochemical parameters and bacterioplankton communities get mixed, this ecotone does not result in increased diversity. Thus unlike terrestrial ecotones, oceanic fronts are boundaries but not hotspots of bacterioplankton diversity in the ocean.


Assuntos
Bactérias/isolamento & purificação , Biodiversidade , Plâncton/isolamento & purificação , Água do Mar/microbiologia , Bactérias/classificação , Bactérias/genética , DNA Bacteriano/genética , Nova Zelândia , Oceanos e Mares , Filogenia , Plâncton/classificação , Plâncton/genética , RNA Ribossômico 16S/genética , Estações do Ano
14.
Front Microbiol ; 9: 3190, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30619234

RESUMO

Marine microbes are an important control on the biogeochemical cycling of trace metals, but simultaneously, these metals can control the growth of microorganisms and the cycling of major nutrients like C and N. However, studies on the response/limitation of microorganisms to trace metals have traditionally focused on the response of autotrophic phytoplankton to Fe fertilization. Few reports are available on the response of heterotrophic prokaryotes to Fe, and even less to other biogeochemically relevant metals. We performed the first study coupling dark incubations with next generation sequencing to specifically target the functional and phylogenetic response of heterotrophic prokaryotes to Fe enrichment. Furthermore, we also studied their response to Co, Mn, Ni, Zn, Cu (individually and mixed), using surface and deep samples from either coastal or open-ocean waters. Heterotrophic prokaryotic activity was stimulated by Fe in surface open-ocean, as well as in coastal, and deep open-ocean waters (where Zn also stimulated). The most susceptible populations to trace metals additions were uncultured bacteria (e.g., SAR324, SAR406, NS9, and DEV007). Interestingly, hydrocarbon-degrading bacteria (e.g., Thalassolituus, Marinobacter, and Oleibacter) benefited the most from metal addition across all waters (regions/depths) revealing a predominant role in the cycling of metals and organic matter in the ocean.

15.
Front Microbiol ; 9: 3296, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30705671

RESUMO

Marine bacterioplankton are essential in global nutrient cycling and organic matter turnover. Time-series analyses, often at monthly sampling frequencies, have established the paramount role of abiotic and biotic variables in structuring bacterioplankton communities and productivities. However, fine-scale seasonal microbial activities, and underlying biological principles, are not fully understood. We report results from four consecutive years of high-frequency time-series sampling in the Baltic Proper. Pronounced temporal dynamics in most investigated microbial variables were observed, including bacterial heterotrophic production, plankton biomass, extracellular enzyme activities, substrate uptake rate constants of glucose, pyruvate, acetate, amino acids, and leucine, as well as nutrient limitation bioassays. Spring blooms consisting of diatoms and dinoflagellates were followed by elevated bacterial heterotrophic production and abundances. During summer, bacterial productivity estimates increased even further, coinciding with an initial cyanobacterial bloom in early July. However, bacterial abundances only increased following a second cyanobacterial bloom, peaking in August. Uptake rate constants for the different measured carbon compounds varied seasonally and inter-annually and were highly correlated to bacterial productivity estimates, temperature, and cyanobacterial abundances. Further, we detected nutrient limitation in response to environmental conditions in a multitude of microbial variables, such as elevated productivities in nutrient bioassays, changes in enzymatic activities, or substrate preferences. Variations among biotic variables often occurred on time scales of days to a few weeks, yet often spanning several sampling occasions. Such dynamics might not have been captured by sampling at monthly intervals, as compared to more predictable transitions in abiotic variables such as temperature or nutrient concentrations. Our study indicates that high resolution analyses of microbial biomass and productivity parameters can help out in the development of biogeochemical and food web models disentangling the microbial black box.

16.
Environ Microbiol ; 19(6): 2301-2319, 2017 06.
Artigo em Inglês | MEDLINE | ID: mdl-28371138

RESUMO

Much of the phenotype of a microorganism consists of its repertoire of metabolisms and how and when its proteins are deployed under different growth conditions. Hence, analyses of protein expression could provide important understanding of how bacteria adapt to different environmental settings. To characterize the flexibility of proteomes of marine bacteria, we investigated protein profiles of three important marine bacterial lineages - Oceanospirillaceae (Neptuniibacter caesariensis strain MED92), Roseobacter (Phaeobacter sp. MED193) and Flavobacteria (Dokdonia sp. MED134) - during transition from exponential to stationary phase. As much as 59-80% of each species' total proteome was expressed. Moreover, all three bacteria profoundly altered their expressed proteomes during growth phase transition, from a dominance of proteins involved in translation to more diverse proteomes, with a striking appearance of enzymes involved in different nutrient-scavenging metabolisms. Whereas the three bacteria shared several overarching metabolic strategies, they differed in important details, including distinct expression patterns of membrane transporters and proteins in carbon and phosphorous metabolism and storage compounds. These differences can be seen as signature metabolisms - metabolisms specific for lineages. These findings suggest that quantitative proteomics can inform about the divergent ecological strategies of marine bacteria in adapting to changes in environmental conditions.


Assuntos
Metabolismo dos Carboidratos/genética , Flavobacteriaceae/metabolismo , Oceanospirillaceae/metabolismo , Transporte Proteico/genética , Roseobacter/metabolismo , Proteínas de Bactérias/metabolismo , Metabolismo dos Carboidratos/fisiologia , Carbono/metabolismo , Flavobacteriaceae/genética , Oceanospirillaceae/genética , Oceanospirillaceae/crescimento & desenvolvimento , Transporte Proteico/fisiologia , Proteoma/metabolismo , Proteômica , Roseobacter/genética , Roseobacter/crescimento & desenvolvimento
17.
Front Microbiol ; 8: 2438, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29354095

RESUMO

Microbes are the engines driving biogeochemical cycles. Microbial extracellular enzymatic activities (EEAs) are the "gatekeepers" of the carbon cycle. The total EEA is the sum of cell-bound (i.e., cell-attached), and dissolved (i.e., cell-free) enzyme activities. Cell-free enzymes make up a substantial proportion (up to 100%) of the total marine EEA. Although we are learning more about how microbial diversity and function (including total EEA) will be affected by environmental changes, little is known about what factors control the importance of the abundant cell-free enzymes. Since cell-attached EEAs are linked to the cell, their fate will likely be linked to the factors controlling the cell's fate. In contrast, cell-free enzymes belong to a kind of "living dead" realm because they are not attached to a living cell but still are able to perform their function away from the cell; and as such, the factors controlling their activity and fate might differ from those affecting cell-attached enzymes. This article aims to place cell-free EEA into the wider context of hydrolysis of organic matter, deal with recent studies assessing what controls the production, activity and lifetime of cell-free EEA, and what their fate might be in response to environmental stressors. This perspective article advocates the need to go "beyond the living things," studying the response of cells/organisms to different stressors, but also to study cell-free enzymes, in order to fully constrain the future and evolution of marine biogeochemical cycles.

18.
Front Microbiol ; 7: 1670, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27818655

RESUMO

To decipher the response of mesopelagic prokaryotic communities to input of nutrients, we tracked changes in prokaryotic abundance, extracellular enzymatic activities, heterotrophic production, dark dissolved inorganic carbon (DIC) fixation, community composition (16S rRNA sequencing) and community gene expression (metatranscriptomics) in 3 microcosm experiments with water from the mesopelagic North Atlantic. Responses in 3 different treatments amended with thiosulfate, ammonium or organic matter (i.e., pyruvate plus acetate) were compared to unamended controls. The strongest stimulation was found in the organic matter enrichments, where all measured rates increased >10-fold. Strikingly, in the organic matter treatment, the dark DIC fixation rates-assumed to be related to autotrophic metabolisms-were equally stimulated as all the other heterotrophic-related parameters. This increase in DIC fixation rates was paralleled by an up-regulation of genes involved in DIC assimilation via anaplerotic pathways. Alkaline phosphatase was the metabolic rate most strongly stimulated and its activity seemed to be related to cross-activation by nonpartner histidine kinases, and/or the activation of genes involved in the regulation of elemental balance during catabolic processes. These findings suggest that episodic events such as strong sedimentation of organic matter into the mesopelagic might trigger rapid increases of originally rare members of the prokaryotic community, enhancing heterotrophic and autotrophic carbon uptake rates, ultimately affecting carbon cycling. Our experiments highlight a number of fairly unstudied microbial processes of potential importance in mesopelagic waters that require future attention.

19.
Environ Microbiol Rep ; 8(1): 132-8, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26636656

RESUMO

Oceanic fronts are widespread mesoscale features that exist in the boundary between different water masses. Despite the recognized importance of bacterioplankton (including bacteria and archaea) on the marine biogeochemical cycles and the ubiquitousness of fronts, the effect of frontal zones on the distribution of bacterioplankton community remains unknown. Using 16S rRNA gene sequencing coupled with a high spatial resolution analysis of the physical properties of the water masses, we demonstrate strong shifts in bacterioplankton community composition (BCC) across the subtropical frontal zone off New Zealand. The transition between water masses resulted in a clear modification of the dominant taxa and a significant increase in community dissimilarity. Our results, linking physical oceanography and marine molecular ecology, support the strong role of oceanic frontal zones in delimiting the distribution of bacterioplankton in the ocean.


Assuntos
Archaea/classificação , Archaea/genética , Bactérias/classificação , Bactérias/genética , Biota , Água do Mar/química , Água do Mar/microbiologia , Fenômenos Químicos , Análise por Conglomerados , DNA Arqueal/química , DNA Arqueal/genética , DNA Bacteriano/química , DNA Bacteriano/genética , DNA Ribossômico/química , DNA Ribossômico/genética , Nova Zelândia , Filogenia , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Análise Espacial
20.
ISME J ; 10(3): 568-81, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26262814

RESUMO

To test whether protist grazing selectively affects the composition of aquatic bacterial communities, we combined high-throughput sequencing to determine bacterial community composition with analyses of grazing rates, protist and bacterial abundances and bacterial cell sizes and physiological states in a mesocosm experiment in which nutrients were added to stimulate a phytoplankton bloom. A large variability was observed in the abundances of bacteria (from 0.7 to 2.4 × 10(6) cells per ml), heterotrophic nanoflagellates (from 0.063 to 2.7 × 10(4) cells per ml) and ciliates (from 100 to 3000 cells per l) during the experiment (∼3-, 45- and 30-fold, respectively), as well as in bulk grazing rates (from 1 to 13 × 10(6) bacteria per ml per day) and bacterial production (from 3 to 379 µg per C l per day) (1 and 2 orders of magnitude, respectively). However, these strong changes in predation pressure did not induce comparable responses in bacterial community composition, indicating that bacterial community structure was resilient to changes in protist predation pressure. Overall, our results indicate that peaks in protist predation (at least those associated with phytoplankton blooms) do not necessarily trigger substantial changes in the composition of coastal marine bacterioplankton communities.


Assuntos
Bactérias/isolamento & purificação , Eucariotos/fisiologia , Fitoplâncton/crescimento & desenvolvimento , Bactérias/classificação , Bactérias/genética , Bactérias/crescimento & desenvolvimento , Biodiversidade , Processos Heterotróficos
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