scholarly journals Hydrogenases and Hydrogen Metabolism of Cyanobacteria

2002 ◽  
Vol 66 (1) ◽  
pp. 1-20 ◽  
Author(s):  
Paula Tamagnini ◽  
Rikard Axelsson ◽  
Pia Lindberg ◽  
Fredrik Oxelfelt ◽  
Röbbe Wünschiers ◽  
...  
Keyword(s):  
Molecular Hydrogen ◽  
Recent Progress ◽  
Gene Products ◽  
Uptake Hydrogenase ◽  
Hydrogen Metabolism ◽  
Nostoc Punctiforme ◽  
Scientific Publications ◽  
Production Of Hydrogen ◽  
Molecular Information ◽  
Pcc 7120

SUMMARY Cyanobacteria may possess several enzymes that are directly involved in dihydrogen metabolism: nitrogenase(s) catalyzing the production of hydrogen concomitantly with the reduction of dinitrogen to ammonia, an uptake hydrogenase (encoded by hupSL) catalyzing the consumption of hydrogen produced by the nitrogenase, and a bidirectional hydrogenase (encoded by hoxFUYH) which has the capacity to both take up and produce hydrogen. This review summarizes our knowledge about cyanobacterial hydrogenases, focusing on recent progress since the first molecular information was published in 1995. It presents the molecular knowledge about cyanobacterial hupSL and hoxFUYH, their corresponding gene products, and their accessory genes before finishing with an applied aspect—the use of cyanobacteria in a biological, renewable production of the future energy carrier molecular hydrogen. In addition to scientific publications, information from three cyanobacterial genomes, the unicellular Synechocystis strain PCC 6803 and the filamentous heterocystous Anabaena strain PCC 7120 and Nostoc punctiforme (PCC 73102/ATCC 29133) is included.

scholarly journals In defence of machine learning: Debunking the myths of artificial intelligence

2018 ◽  
Vol 14 (4) ◽  
pp. 734-747 ◽  
Author(s):  
Constance de Saint Laurent
Keyword(s):  
Artificial Intelligence ◽  
Machine Learning ◽  
Recent Progress ◽  
Life Time ◽  
Clear Understanding ◽  
Social Scientists ◽  
Scientific Publications ◽  
The Past ◽  
Potential Benefits ◽  
The Media

There has been much hype, over the past few years, about the recent progress of artificial intelligence (AI), especially through machine learning. If one is to believe many of the headlines that have proliferated in the media, as well as in an increasing number of scientific publications, it would seem that AI is now capable of creating and learning in ways that are starting to resemble what humans can do. And so that we should start to hope – or fear – that the creation of fully cognisant machine might be something we will witness in our life time. However, much of these beliefs are based on deep misconceptions about what AI can do, and how. In this paper, I start with a brief introduction to the principles of AI, machine learning, and neural networks, primarily intended for psychologists and social scientists, who often have much to contribute to the debates surrounding AI but lack a clear understanding of what it can currently do and how it works. I then debunk four common myths associated with AI: 1) it can create, 2) it can learn, 3) it is neutral and objective, and 4) it can solve ethically and/or culturally sensitive problems. In a third and last section, I argue that these misconceptions represent four main dangers: 1) avoiding debate, 2) naturalising our biases, 3) deresponsibilising creators and users, and 4) missing out some of the potential uses of machine learning. I finally conclude on the potential benefits of using machine learning in research, and thus on the need to defend machine learning without romanticising what it can actually do.

scholarly journals Identification of Sesquiterpene Synthases from Nostoc punctiforme PCC 73102 and Nostoc sp. Strain PCC 7120

2008 ◽  
Vol 190 (18) ◽  
pp. 6084-6096 ◽  
Author(s):  
Sean A. Agger ◽  
Fernando Lopez-Gallego ◽  
Thomas R. Hoye ◽  
Claudia Schmidt-Dannert
Keyword(s):  
Functional Expression ◽  
Terpene Synthase ◽  
Putative Hybrid ◽  
Nostoc Punctiforme ◽  
Terpene Synthases ◽  
E Coli ◽  
Reductase Gene ◽  
Pcc 7120 ◽  
Defense Compound

ABSTRACT Cyanobacteria are a rich source of natural products and are known to produce terpenoids. These bacteria are the major source of the musty-smelling terpenes geosmin and 2-methylisoborneol, which are found in many natural water supplies; however, no terpene synthases have been characterized from these organisms to date. Here, we describe the characterization of three sesquiterpene synthases identified in Nostoc sp. strain PCC 7120 (terpene synthase NS1) and Nostoc punctiforme PCC 73102 (terpene synthases NP1 and NP2). The second terpene synthase in N. punctiforme (NP2) is homologous to fusion-type sesquiterpene synthases from Streptomyces spp. shown to produce geosmin via an intermediate germacradienol. The enzymes were functionally expressed in Escherichia coli, and their terpene products were structurally identified as germacrene A (from NS1), the eudesmadiene 8a-epi-α-selinene (from NP1), and germacradienol (from NP2). The product of NP1, 8a-epi-α-selinene, so far has been isolated only from termites, in which it functions as a defense compound. Terpene synthases NP1 and NS1 are part of an apparent minicluster that includes a P450 and a putative hybrid two-component protein located downstream of the terpene synthases. Coexpression of P450 genes with their adjacent located terpene synthase genes in E. coli demonstrates that the P450 from Nostoc sp. can be functionally expressed in E. coli when coexpressed with a ferredoxin gene and a ferredoxin reductase gene from Nostoc and that the enzyme oxygenates the NS1 terpene product germacrene A. This represents to the best of our knowledge the first example of functional expression of a cyanobacterial P450 in E. coli.

Development and evolution

1997 ◽  
Author(s):  
John Maynard Smith ◽  
Eors Szathmary
Keyword(s):  
Evolutionary Biology ◽  
Recent Progress ◽  
Sound Production ◽  
Germ Line ◽  
Black Box ◽  
Developmental Genetics ◽  
Morphological Form ◽  
Molecular Information ◽  
Acquired Characters ◽  
Development And Evolution

In the nineteenth century, ideas about development, heredity and evolution were inextricably mixed up, because it seemed natural to suppose that changes that first occurred in development could become hereditary, and so could contribute to evolution. This was not only Lamarck’s view but Darwin’s, expressed in his theory of pangenesis. Weismann liberated us from this confusion, by arguing that information could pass from germ line to soma, but not from soma to germ line. If he was right, geneticists and evolutionary biologists could treat development as a black box: transmission genetics and evolution could be understood without first having to understand development. Since Weismann, developmental biology has had only a rather marginal impact on evolutionary biology. One day, we have promised ourselves, we will open the box, but for the time being we can get along very nicely without doing so. Recent progress in developmental genetics, some of which has been reviewed in the last three chapters, oblige us to reopen the question. In fact, there are three related questions, not one. The first, which is most relevant to the theme of this book, is the ‘levels of selection’ question: why does not selection between the cells of an organism disrupt integration at the level of the organism? This is the topic of section 15.2. The second is the problem of the inheritance of acquired characters. This old problem has reappeared in a new guise. We now recognize the existence of cell heredity, mediated by different mechanisms from those concerned with transmitting information between generations. In section 15.3, we discuss whether cell heredity plays any role in evolutionary change. Finally, in sections 15.4 and 15.5, we ask whether recent molecular information sheds any light on another old problem—that of the extraordinary conservatism of morphological form, maintained despite dramatic changes of function. This conservatism has led anatomists to identify a small number of basic archetypes, or bauplans. There is little doubt that conservatism is real. Consider, for example, the fact that bones and cartilages, which in humans serve in swallowing, sound production and hearing, are derived from elements of the gill apparatus whereby our fish ancestors exchanged gases with seawater, and, before that, in all probability, from elements of a filter-feeding apparatus.

scholarly journals Diversity and transcription of proteases involved in the maturation of hydrogenases in Nostoc punctiforme ATCC 29133 and Nostoc sp. strain PCC 7120

2009 ◽  
Vol 9 (1) ◽  
pp. 53 ◽  
Author(s):  
Ellenor Devine ◽  
Marie Holmqvist ◽  
Karin Stensjö ◽  
Peter Lindblad
Keyword(s):  
Nostoc Punctiforme ◽  
Pcc 7120

A review of metal oxynitrides for photocatalysis

2016 ◽  
Vol 3 (5) ◽  
pp. 578-590 ◽  
Author(s):  
Manan Ahmed ◽  
Guo Xinxin
Keyword(s):  
Visible Light ◽  
Visible Light Irradiation ◽  
Recent Progress ◽  
Light Irradiation ◽  
Production Of Hydrogen

This review highlights the recent progress in the production of hydrogen using a metal oxynitride photocatalyst under visible light irradiation.

scholarly journals Transcription of hupSL in Anabaena variabilis ATCC 29413 Is Regulated by NtcA and Not by Hydrogen

2008 ◽  
Vol 74 (7) ◽  
pp. 2103-2110 ◽  
Author(s):  
Philip D. Weyman ◽  
Brenda Pratte ◽  
Teresa Thiel
Keyword(s):  
Nitrogen Fixation ◽  
Binding Site ◽  
Hydrogen Gas ◽  
Anabaena Variabilis ◽  
Uptake Hydrogenase ◽  
Transcriptional Reporter ◽  
Exogenous Addition ◽  
Step Down ◽  
Additional Level ◽  
Pcc 7120

ABSTRACT Nitrogen-fixing cyanobacteria such as Anabaena variabilis ATCC 29413 use an uptake hydrogenase, encoded by hupSL, to recycle hydrogen gas that is produced as an obligate by-product of nitrogen fixation. The regulation of hupSL in A. variabilis is likely to differ from that of the closely related Anabaena sp. strain PCC 7120 because A. variabilis lacks the excision element-mediated regulation that characterizes hupSL regulation in strain PCC 7120. An analysis of the hupSL transcript in a nitrogenase mutant of A. variabilis that does not produce any detectable hydrogen indicated that neither nitrogen fixation nor hydrogen gas was required for the induction of hupSL. Furthermore, exogenous addition of hydrogen gas did not stimulate hupSL transcription. Transcriptional reporter constructs indicated that the accumulation of hupSL transcript after nitrogen step-down was restricted primarily to the microaerobic heterocysts. Anoxic conditions were not sufficient to induce hupSL transcription. The induction of hupSL after nitrogen step-down was reduced in a mutant in the global nitrogen regulator NtcA, but was not reduced in a mutant unable to form heterocysts. A consensus NtcA-binding site was identified upstream of hupSL, and NtcA was found to bind to this region. Thus, while neither hydrogen gas nor anoxia controlled the expression of hupSL, its expression was controlled by NtcA. Heterocyst differentiation was not required for hupSL induction in response to nitrogen step-down, but heterocyst-localized cues may add an additional level of regulation to hupSL.

Hydrogenation of polar functionalities with Cp*Ru(PN) catalysts

2008 ◽  
Vol 80 (5) ◽  
pp. 1047-1053 ◽  
Author(s):  
Masato Ito
Keyword(s):  
Molecular Hydrogen ◽  
Structural Modification ◽  
Recent Progress ◽  
Catalytic Performance ◽  
Efficient Access ◽  
Synthetic Intermediates ◽  
Molecular Catalysts

This account deals with an overview of our recent progress toward the development of molecular catalysts for the reduction in polar functionalities with molecular hydrogen (H2). An emphasis is placed on the newly designed Cp*Ru(PN) complexes, which have been identified as efficient catalysts for the hydrogenation of imides. The structural modification of the complex enhances the catalytic performance and allows efficient access to various chiral synthetic intermediates.

Turning around the electron flow in an uptake hydrogenase. EPR spectroscopy and in vivo activity of a designed mutant in HupSL from Nostoc punctiforme

2016 ◽  
Vol 9 (2) ◽  
pp. 581-594 ◽  
Author(s):  
Patrícia Raleiras ◽  
Namita Khanna ◽  
Hélder Miranda ◽  
Lívia S. Mészáros ◽  
Henning Krassen ◽  
...  
Keyword(s):  
Point Mutation ◽  
Epr Spectroscopy ◽  
Electron Flow ◽  
Single Point ◽  
Single Point Mutation ◽  
Uptake Hydrogenase ◽  
Nostoc Punctiforme

The uptake hydrogenase HupSL became a H2 producer in N. punctiforme after modifying the proximal FeS cluster with the single point mutation C12P.

scholarly journals Hydrogen Metabolism inHelicobacter pyloriPlays a Role in Gastric Carcinogenesis through Facilitating CagA Translocation

mBio ◽  
2016 ◽  
Vol 7 (4) ◽  
Author(s):  
Ge Wang ◽  
Judith Romero-Gallo ◽  
Stéphane L. Benoit ◽  
M. Blanca Piazuelo ◽  
Ricardo L. Dominguez ◽  
...  
Keyword(s):  
Gastric Cancer ◽  
Cancer Risk ◽  
Respiratory Chain ◽  
Molecular Hydrogen ◽  
Gastric Carcinogenesis ◽  
Hydrogenase Activity ◽  
Hydrogen Metabolism ◽  
Gastric Cancer Risk ◽  
Ags Cells ◽  
H Pylori

ABSTRACTA known virulence factor ofHelicobacter pylorithat augments gastric cancer risk is the CagA cytotoxin. A carcinogenic derivative strain, 7.13, that has a greater ability to translocate CagA exhibits much higher hydrogenase activity than its parent noncarcinogenic strain, B128. A Δhydmutant strain with deletion of hydrogenase genes was ineffective in CagA translocation into human gastric epithelial AGS cells, while no significant attenuation of cell adhesion was observed. The quinone reductase inhibitor 2-n-heptyl-4-hydroxyquinoline-N-oxide (HQNO) was used to specifically inhibit the H2-utilizing respiratory chain of outer membrane-permeabilized bacterial cells; that level of inhibitor also greatly attenuated CagA translocation into AGS cells, indicating the H2-generated transmembrane potential is a contributor to toxin translocation. The Δhydstrain showed a decreased frequency of DNA transformation, suggesting thatH. pylorihydrogenase is also involved in energizing the DNA uptake apparatus. In a gerbil model of infection, the ability of the Δhydstrain to induce inflammation was significantly attenuated (at 12 weeks postinoculation), while all of the gerbils infected with the parent strain (7.13) exhibited a high level of inflammation. Gastric cancer developed in 50% of gerbils infected with the wild-type strain 7.13 but in none of the animals infected with the Δhydstrain. By examining the hydrogenase activities from well-defined clinicalH. pyloriisolates, we observed that strains isolated from cancer patients (n= 6) have a significantly higher hydrogenase (H2/O2) activity than the strains isolated from gastritis patients (n= 6), further supporting an association betweenH. pylorihydrogenase activity and gastric carcinogenesis in humans.IMPORTANCEHydrogen-utilizing hydrogenases are known to be important for some respiratory pathogens to colonize hosts. Here a gastric cancer connection is made via a pathogen’s (H. pylori) use of molecular hydrogen, a host microbiome-produced gas. Delivery of the known carcinogenic factor CagA into host cells is augmented by the H2-utilizing respiratory chain of the bacterium. The role of hydrogenase in carcinogenesis is demonstrated in an animal model, whereby inflammation markers and cancer development were attenuated in the hydrogenase-null strain. Hydrogenase activity comparisons of clinical strains of the pathogen also support a connection between hydrogen metabolism and gastric cancer risk. While molecular hydrogen use is acknowledged to be an alternative high-energy substrate for some pathogens, this work extends the roles of H2oxidation to include transport of a carcinogenic toxin. The work provides a new avenue for exploratory treatment of some cancers via microflora alterations.

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