scholarly journals Cryptic Cycling of Complexes Containing Fe(III) and Organic Matter by Phototrophic Fe(II)-Oxidizing Bacteria

2019 ◽  
Vol 85 (8) ◽  
Author(s):  
Chao Peng ◽  
Casey Bryce ◽  
Anneli Sundman ◽  
Andreas Kappler
Keyword(s):  
Organic Matter ◽  
Anoxygenic Phototrophic Bacteria ◽  
Aquatic Environments ◽  
Photic Zone ◽  
Iron Cycling ◽  
Microbial Oxidation ◽  
Photochemical Reduction ◽  
Content Type ◽  
Dissolved Iron ◽  
New Type

ABSTRACTFe-organic matter (Fe-OM) complexes are abundant in the environment and, due to their mobility, reactivity, and bioavailability, play a significant role in the biogeochemical Fe cycle. In photic zones of aquatic environments, Fe-OM complexes can potentially be reduced and oxidized, and thus cycled, by light-dependent processes, including abiotic photoreduction of Fe(III)-OM complexes and microbial oxidation of Fe(II)-OM complexes, by anoxygenic phototrophic bacteria. This could lead to a cryptic iron cycle in which continuous oxidation and rereduction of Fe could result in a low and steady-state Fe(II) concentration despite rapid Fe turnover. However, the coupling of these processes has never been demonstrated experimentally. In this study, we grew a model anoxygenic phototrophic Fe(II) oxidizer,Rhodobacter ferrooxidansSW2, with either citrate, Fe(II)-citrate, or Fe(III)-citrate. We found that strain SW2 was capable of reoxidizing Fe(II)-citrate produced by photochemical reduction of Fe(III)-citrate, which kept the dissolved Fe(II)-citrate concentration at low (<10 μM) and stable concentrations, with a concomitant increase in cell numbers. Cell suspension incubations with strain SW2 showed that it can also oxidize Fe(II)-EDTA, Fe(II)-humic acid, and Fe(II)-fulvic acid complexes. This work demonstrates the potential for active cryptic Fe cycling in the photic zone of anoxic aquatic environments, despite low measurable Fe(II) concentrations which are controlled by the rate of microbial Fe(II) oxidation and the identity of the Fe-OM complexes.IMPORTANCEIron cycling, including reduction of Fe(III) and oxidation of Fe(II), involves the formation, transformation, and dissolution of minerals and dissolved iron-organic matter compounds. It has been shown previously that Fe can be cycled so rapidly that no measurable changes in Fe(II) and Fe(III) concentrations occur, leading to a so-called cryptic cycle. Cryptic Fe cycles have been shown to be driven either abiotically by a combination of photochemical reduction of Fe(III)-OM complexes and reoxidation of Fe(II) by O2, or microbially by a combination of Fe(III)-reducing and Fe(II)-oxidizing bacteria. Our study demonstrates a new type of light-driven cryptic Fe cycle that is relevant for the photic zone of aquatic habitats involving abiotic photochemical reduction of Fe(III)-OM complexes and microbial phototrophic Fe(II) oxidation. This new type of cryptic Fe cycle has important implications for biogeochemical cycling of iron, carbon, nutrients, and heavy metals and can also influence the composition and activity of microbial communities.

scholarly journals Complete Genomic Sequence of Pseudoalteromonas sp. Strain SAO4-4, a Protease-Producing Bacterium Isolated from Seawater of the Atlantic Ocean

2018 ◽  
Vol 6 (22) ◽  
Author(s):  
Bai-Lu Tang ◽  
Jin-Cheng Rong ◽  
Yan-Ru Dang ◽  
Bin-Bin Xie ◽  
Xiu-Lan Chen ◽  
...  
Keyword(s):  
Organic Matter ◽  
Atlantic Ocean ◽  
Genome Sequence ◽  
Complete Genome ◽  
Genomic Sequence ◽  
Aquatic Environments ◽  
Complete Genomic Sequence ◽  
Content Type ◽  
Circular Chromosomes ◽  
Complete Genomic

ABSTRACT The complete genome of Pseudoalteromonas sp. strain SAO4-4, a protease-producing bacterium from seawater, is composed of two circular chromosomes and one plasmid. This genome sequence will provide a better understanding of the ecological roles of protease-producing bacteria in the degradation of organic matter in marine aquatic environments.

scholarly journals Evaluation of Daphnid Grazing on Microscopic Zoosporic Fungi by Using Comparative Threshold Cycle Quantitative PCR

2016 ◽  
Vol 82 (13) ◽  
pp. 3868-3874 ◽  
Author(s):  
Michelle A. Maier ◽  
Kimiko Uchii ◽  
Tawnya D. Peterson ◽  
Maiko Kagami
Keyword(s):  
Organic Matter ◽  
Food Web ◽  
Food Webs ◽  
Quantitative Pcr ◽  
Morphological Characteristics ◽  
Life Cycles ◽  
Molecular Techniques ◽  
Aquatic Environments ◽  
Content Type ◽  
Zoosporic Fungi

ABSTRACTLethal parasitism of large phytoplankton by chytrids (microscopic zoosporic fungi) may play an important role in organic matter and nutrient cycling in aquatic environments by shunting carbon away from hosts and into much smaller zoospores, which are more readily consumed by zooplankton. This pathway provides a mechanism to more efficiently retain carbon within food webs and reduce export losses. However, challenges in accurate identification and quantification of chytrids have prevented a robust assessment of the relative importance of parasitism for carbon and energy flows within aquatic systems. The use of molecular techniques has greatly advanced our ability to detect small, nondescript microorganisms in aquatic environments in recent years, including chytrids. We used quantitative PCR (qPCR) to quantify the consumption of zoospores byDaphniain laboratory experiments using a culture-based comparative threshold cycle (CT) method. We successfully quantified the reduction of zoospores in water samples duringDaphniagrazing and confirmed the presence of chytrid DNA inside the daphnid gut. We demonstrate that comparativeCTqPCR is a robust and effective method to quantify zoospores and evaluate zoospore grazing by zooplankton and will aid in better understanding how chytrids contribute to organic matter cycling and trophic energy transfer within food webs.IMPORTANCEThe study of aquatic fungi is often complicated by the fact that they possess complex life cycles that include a variety of morphological forms. Studies that rely on morphological characteristics to quantify the abundances of all stages of the fungal life cycle face the challenge of correctly identifying and enumerating the nondescript zoospores. These zoospores, however, provide an important trophic link between large colonial phytoplankton and zooplankton: that is, once the carbon is liberated from phytoplankton into the parasitic zoospores, the latter are consumed by zooplankton and carbon is retained in the aquatic food web rather than exported from the system. This study provides a tool to quantify zoospores and evaluate the consumption of zoospores by zooplankton in order to further our understanding of their role in food web dynamics.

scholarly journals Accumulation and Dissolution of Magnetite Crystals in a Magnetically Responsive Ciliate

2018 ◽  
Vol 84 (8) ◽  
pp. e02865-17 ◽  
Author(s):  
Caroline L. Monteil ◽  
Nicolas Menguy ◽  
Sandra Prévéral ◽  
Alan Warren ◽  
David Pignol ◽  
...  
Keyword(s):  
Magnetic Particles ◽  
Light And Electron Microscopy ◽  
Magnetotactic Bacteria ◽  
Aquatic Environments ◽  
Aquatic Habitats ◽  
Iron Cycling ◽  
Ecological Processes ◽  
Content Type ◽  
Particulate Iron ◽  
High Concentrations

ABSTRACTMagnetotactic bacteria (MTB) represent a group of microorganisms that are widespread in aquatic habitats and thrive at oxic-anoxic interfaces. They are able to scavenge high concentrations of iron thanks to the biomineralization of magnetic crystals in their unique organelles, the so-called magnetosome chains. Although their biodiversity has been intensively studied, their ecology and impact on iron cycling remain largely unexplored. Predation by protozoa was suggested as one of the ecological processes that could be involved in the release of iron back into the ecosystem. Magnetic protozoa were previously observed in aquatic environments, but their diversity and the fate of particulate iron during grazing are poorly documented. In this study, we report the morphological and molecular characterizations of a magnetically responsive MTB-grazing protozoan able to ingest high quantities of MTB. This protozoan is tentatively identified asUronema marinum, a ciliate known to be a predator of bacteria. Using light and electron microscopy, we investigated in detail the vacuoles in which the lysis of phagocytized prokaryotes occurs. We carried out high-resolution observations of aligned magnetosome chains and ongoing dissolution of crystals. Particulate iron in the ciliate represented approximately 0.01% of its total volume. We show the ubiquity of this interaction in other types of environments and describe different grazing strategies. These data contribute to the mounting evidence that the interactions between MTB and protozoa might play a significant role in iron turnover in microaerophilic habitats.IMPORTANCEIdentifying participants of each biogeochemical cycle is a prerequisite to our understanding of ecosystem functioning. Magnetotactic bacteria (MTB) participate in iron cycling by concentrating large amounts of biomineralized iron minerals in their cells, which impacts their chemical environment at, or below, the oxic-anoxic transition zone in aquatic habitats. It was shown that some protozoa inhabiting this niche could become magnetic by the ingestion of magnetic crystals biomineralized by grazed MTB. In this study, we show that magnetic MTB grazers are commonly observed in marine and freshwater sediments and can sometimes accumulate very large amounts of particulate iron. We describe here different phagocytosis strategies, determined using magnetic particles from MTB as tracers after their ingestion by the protozoa. This study paves the way for potential scientific or medical applications using MTB grazers as magnetosome hyperaccumulators.

Earth’s Middle Ages: What Came after the GOE

2017 ◽  
Author(s):  
Donald Eugene Canfield
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Middle Ages ◽  
Atmospheric Oxygen ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Dissolved Iron ◽  
Great Oxidation Event ◽  
Low Levels ◽  
Substantial Rise

This chapter considers the aftermath of the great oxidation event (GOE). It suggests that there was a substantial rise in oxygen defining the GOE, which may, in turn have led to the Lomagundi isotope excursion, which was associated with high rates of organic matter burial and perhaps even higher concentrations of oxygen. This excursion was soon followed by a crash in oxygen to very low levels and a return to banded iron formation deposition. When the massive amounts of organic carbon buried during the excursion were brought into the weathering environment, they would have represented a huge oxygen sink, drawing down levels of atmospheric oxygen. There appeared to be a veritable seesaw in oxygen concentrations, apparently triggered initially by the GOE. The GOE did not produce enough oxygen to oxygenate the oceans. Dissolved iron was removed from the oceans not by reaction with oxygen but rather by reaction with sulfide. Thus, the deep oceans remained anoxic and became rich in sulfide, instead of becoming well oxygenated.

Characterization and biogeochemical implications of dissolved organic matter in aquatic environments

2021 ◽  
Vol 294 ◽  
pp. 113041
Author(s):  
Hengfeng Zhang ◽  
Yucong Zheng ◽  
Xiaochang C. Wang ◽  
Yongkun Wang ◽  
Mawuli Dzakpasu
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Aquatic Environments

Toward a theory on workplaces for smart workers

Facilities ◽  
2019 ◽  
Vol 38 (3/4) ◽  
pp. 298-315
Author(s):  
Luisa Errichiello ◽  
Tommasina Pianese
Keyword(s):  
Web Sites ◽  
Participant Observation ◽  
Secondary Data ◽  
Primary Data ◽  
Innovative Design ◽  
Content Type ◽  
New Type ◽  
Smart Working ◽  
Research Propositions

Purpose The purpose of this paper is to identify the main features of smart work centers (SWCs) and show how these innovative offices would support the implementation of smart working and related changes in workspaces (“bricks”), technologies (“bytes”) and organizational practices (“behaviors”). Design/methodology/approach In this study, scientific literature is combined with white papers and business reports and visits to 14 workplaces, including offices designed as SWCs, co-working spaces, one telecenter, one accelerator and one fab lab. Primary data were collected through interviews with managers and users and non-participant observation, whereas secondary data included web-sites, brochures, presentations, press releases and official documents. Findings The authors developed research propositions about how the design of spaces and the availability of technology within SWCs would support the “bricks” and “bytes” levers of smart working. More importantly, the authors assumed that this new type of workplace would sustain changes in employees’ behaviors and managers’ practices, thus helping to overcome several challenges traditionally associated with remote working. Research limitations/implications The exploratory nature of the research only provides preliminary information about the role of SWCs within smart working programs. Additional qualitative and quantitative empirical investigation is required. Practical implications This study provides valuable knowledge about how the design of corporate offices can be leveraged to sustain the implementation of smart working. Originality/value This study advances knowledge on workplaces by focusing on an innovative design of traditional offices (SWC). It also lays the foundations for future investigation aimed at testing the developed propositions.

scholarly journals Calvin Cycle Flux, Pathway Constraints, and Substrate Oxidation State Together Determine the H2 Biofuel Yield in Photoheterotrophic Bacteria

mBio ◽  
2011 ◽  
Vol 2 (2) ◽  
Author(s):  
James B. McKinlay ◽  
Caroline S. Harwood
Keyword(s):  
Organic Compounds ◽  
Oxidation State ◽  
Rhodopseudomonas Palustris ◽  
Calvin Cycle ◽  
Substrate Oxidation ◽  
Hydrogen Gas ◽  
Anaerobic Growth ◽  
Anoxygenic Phototrophic Bacteria ◽  
Transportation Fuel ◽  
Content Type

ABSTRACTHydrogen gas (H2) is a possible future transportation fuel that can be produced by anoxygenic phototrophic bacteria via nitrogenase. The electrons for H2are usually derived from organic compounds. Thus, one would expect more H2to be produced when anoxygenic phototrophs are supplied with increasingly reduced (electron-rich) organic compounds. However, the H2yield does not always differ according to the substrate oxidation state. To understand other factors that influence the H2yield, we determined metabolic fluxes inRhodopseudomonas palustrisgrown on13C-labeled fumarate, succinate, acetate, and butyrate (in order from most oxidized to most reduced). The flux maps revealed that the H2yield was influenced by two main factors in addition to substrate oxidation state. The first factor was the route that a substrate took to biosynthetic precursors. For example, succinate took a different route to acetyl-coenzyme A (CoA) than acetate. As a result,R. palustrisgenerated similar amounts of reducing equivalents and similar amounts of H2from both succinate and acetate, even though succinate is more oxidized than acetate. The second factor affecting the H2yield was the amount of Calvin cycle flux competing for electrons. When nitrogenase was active, electrons were diverted away from the Calvin cycle towards H2, but to various extents, depending on the substrate. When Calvin cycle flux was blocked, the H2yield increased during growth on all substrates. In general, this increase in H2yield could be predicted from the initial Calvin cycle flux.IMPORTANCEPhotoheterotrophic bacteria, likeRhodopseudomonas palustris, obtain energy from light and carbon from organic compounds during anaerobic growth. Cells can naturally produce the biofuel H2as a way of disposing of excess electrons. Unexpectedly, feeding cells organic compounds with more electrons does not necessarily result in more H2. Despite repeated observations over the last 40 years, the reasons for this discrepancy have remained unclear. In this paper, we identified two metabolic factors that influence the H2yield, (i) the route taken to make biosynthetic precursors and (ii) the amount of CO2-fixing Calvin cycle flux that competes against H2production for electrons. We show that the H2yield can be improved on all substrates by using a strain that is incapable of Calvin cycle flux. We also contributed quantitative knowledge to the long-standing question of why photoheterotrophs must produce H2or fix CO2even on relatively oxidized substrates.

scholarly journals Differing Growth Responses of Major Phylogenetic Groups of Marine Bacteria to Natural Phytoplankton Blooms in the Western North Pacific Ocean

2011 ◽  
Vol 77 (12) ◽  
pp. 4055-4065 ◽  
Author(s):  
Yuya Tada ◽  
Akito Taniguchi ◽  
Ippei Nagao ◽  
Takeshi Miki ◽  
Mitsuo Uematsu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Bacterial Community ◽  
North Pacific ◽  
Bacterial Production ◽  
Western North Pacific ◽  
Bacterial Abundance ◽  
North Pacific Ocean ◽  
Growth Potential ◽  
Phytoplankton Blooms ◽  
Content Type

ABSTRACTGrowth and productivity of phytoplankton substantially change organic matter characteristics, which affect bacterial abundance, productivity, and community structure in aquatic ecosystems. We analyzed bacterial community structures and measured activities inside and outside phytoplankton blooms in the western North Pacific Ocean by using bromodeoxyuridine immunocytochemistry and fluorescencein situhybridization (BIC-FISH).Roseobacter/Rhodobacter, SAR11,Betaproteobacteria,Alteromonas, SAR86, andBacteroidetesresponded differently to changes in organic matter supply.Roseobacter/Rhodobacterbacteria remained widespread, active, and proliferating despite large fluctuations in organic matter and chlorophylla(Chl-a) concentrations. The relative contribution ofBacteroidetesto total bacterial production was consistently high. Furthermore, we documented the unexpectedly large contribution ofAlteromonasto total bacterial production in the bloom. Bacterial abundance, productivity, and growth potential (the proportion of growing cells in a population) were significantly correlated with Chl-aand particulate organic carbon concentrations. Canonical correspondence analysis showed that organic matter supply was critical for determining bacterial community structures. The growth potential of each bacterial group as a function of Chl-aconcentration showed a bell-shaped distribution, indicating an optimal organic matter concentration to promote growth. The growth ofAlteromonasandBetaproteobacteriawas especially strongly correlated with organic matter supply. These data elucidate the distinctive ecological role of major bacterial taxa in organic matter cycling during open ocean phytoplankton blooms.

scholarly journals Establishment and Application of Rapid Diagnosis for Reverse Transcription-Quantitative PCR of Newly Emerging Goose-Origin Nephrotic Astrovirus in China

mSphere ◽  
2018 ◽  
Vol 3 (6) ◽  
Author(s):  
Xiaoyuan Yuan ◽  
Kai Meng ◽  
Yuxia Zhang ◽  
Lihong Qi ◽  
Wu Ai ◽  
...  
Keyword(s):  
Quantitative Pcr ◽  
Clinical Application ◽  
Reverse Transcription ◽  
Test Sample ◽  
Sensitivity Testing ◽  
Content Type ◽  
Reverse Transcription Quantitative Pcr ◽  
Emerging Virus ◽  
New Type ◽  
And Control

ABSTRACT In 2017, a new type of goose-origin astrovirus (GoAstV) that is completely different from previously identified avian astroviruses (which have only 30.0% to 50.5% homology with GoAstV) has been isolated from diseased geese in China. This disease can cause joint swelling in sick geese, and the anatomy shows a clear precipitation of urate in the kidney. The rate of death and culling can reach more than 30%, revealing the disease’s severe pathogenicity. To quickly and accurately diagnose the newly emerging disease, we established a highly specific reverse transcription-quantitative PCR (RT-qPCR) method of detecting GoAstV. Sensitivity testing showed that the minimum amount of test sample for this method is 52.5 copies/μl. Clinical application confirmed that this method can quickly and effectively detect GoAstV, providing a diagnostic platform for the prevention and control of goose disease. IMPORTANCE Goose-origin astrovirus (GoAstV), as a newly emerging virus in 2017, is different from previously known astroviruses in the genus Avastrovirus. So far, few studies have focused on the novel virus. Considering the infectious development of astrovirus (AstV), we established a reverse transcription-quantitative PCR (RT-qPCR) assay with a strong specificity to quickly and accurately diagnose GoAstV. Confirmed by clinical application, this method can quickly and accurately detect prevalent GoAstV. The assay is thus convenient for clinical operation and is applicable to the monitoring of GoAstV disease.

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