Nitric Oxide: Interaction with the Ammonia Monooxygenase and Regulation of Metabolic Activities in Ammonia Oxidizers

ABSTRACTNitrite reductase (NirK) and nitric oxide reductase (NorB) have long been thought to play an essential role in nitrous oxide (N2O) production by ammonia-oxidizing bacteria. However, essential gaps remain in our understanding of how and when NirK and NorB are active and functional, putting into question their precise roles in N2O production by ammonia oxidizers. The growth phenotypes of theNitrosomonas europaeaATCC 19718 wild-type and mutant strains deficient in expression of NirK, NorB, and both gene products were compared under atmospheric and reduced O2tensions. Anoxic resting-cell assays and instantaneous nitrite (NO2−) reduction experiments were done to assess the ability of the wild-type and mutantN. europaeastrains to produce N2O through the nitrifier denitrification pathway. Results confirmed the role of NirK for efficient substrate oxidation ofN. europaeaand showed that NorB is involved in N2O production during growth at both atmospheric and reduced O2tensions. Anoxic resting-cell assays and measurements of instantaneous NO2−reduction using hydrazine as an electron donor revealed that an alternate nitrite reductase to NirK is present and active. These experiments also clearly demonstrated that NorB was the sole nitric oxide reductase for nitrifier denitrification. The results of this study expand the enzymology for nitrogen metabolism and N2O production byN. europaeaand will be useful to interpret pathways in other ammonia oxidizers that lack NirK and/or NorB genes.

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Pacific Northwest Marine Sediments Contain Ammonia-Oxidizing Bacteria in the β Subdivision of theProteobacteria

Applied and Environmental Microbiology ◽

10.1128/aem.66.10.4532-4535.2000 ◽

2000 ◽

Vol 66 (10) ◽

pp. 4532-4535 ◽

Cited By ~ 81

Author(s):

Stephen C. Nold ◽

Jizhong Zhou ◽

Allan H. Devol ◽

James M. Tiedje

Keyword(s):

Pacific Northwest ◽

Marine Sediments ◽

Marine Sediment ◽

Ammonia Oxidizing Bacteria ◽

Ammonia Oxidizers ◽

Ammonia Monooxygenase ◽

Gene Sequences ◽

Freshwater Sediments ◽

Aquatic Sediments ◽

Monooxygenase Gene

ABSTRACT The diversity of ammonia-oxidizing bacteria in aquatic sediments was studied by retrieving ammonia monooxygenase and methane monooxygenase gene sequences. Methanotrophs dominated freshwater sediments, while β-proteobacterial ammonia oxidizers dominated marine sediments. These results suggest that γ-proteobacteria such asNitrosococcus oceani are minor members of marine sediment ammonia-oxidizing communities.

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Reduction of spermatogonia and testosterone in rat testes flown on space lab-3

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100142864 ◽

1986 ◽

Vol 44 ◽

pp. 248-249

Author(s):

Delbert E. Philpott ◽

W. Sapp ◽

C. Williams ◽

T. Fast ◽

J. Stevenson ◽

...

Keyword(s):

Social Interaction ◽

Social Status ◽

Population Size ◽

Physiological Response ◽

Social Rank ◽

Reproductive Function ◽

Testicular Development ◽

Organ Weights ◽

Reproductive Maturation ◽

Metabolic Activities

Space Lab 3 (SL-3) was flown on Shuttle Challenger providing an opportunity to measure the effect of spaceflight on rat testes. Cannon developed the idea that organisms react to unfavorable conditions with highly integrated metabolic activities. Selye summarized the manifestations of physiological response to nonspecific stress and he pointed out that atrophy of the gonads always occurred. Many papers have been published showing the effects of social interaction, crowding, peck order and confinement. Flickinger showed delayed testicular development in subordinate roosters influenced by group numbers, social rank and social status. Christian reported increasing population size in mice resulted in adrenal hypertrophy, inhibition of reproductive maturation and loss of reproductive function in adults. Sex organ weights also declined. Two male dogs were flown on Cosmos 110 for 22 days. Fedorova reported an increase of 30 to 70% atypical spermatozoa consisting of tail curling and/or the absence of a tail.

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Localization of endothelial nitric oxide synthase in the normal and failing human atrial myocardium

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100166397 ◽

1996 ◽

Vol 54 ◽

pp. 786-787

Author(s):

Chi-Ming Wei ◽

Margarita Bracamonte ◽

Shi-Wen Jiang ◽

Richard C. Daly ◽

Christopher G.A. McGregor ◽

...

Keyword(s):

Nitric Oxide ◽

Heart Failure ◽

Nitric Oxide Synthase ◽

Endothelial Nitric Oxide Synthase ◽

Cardiac Tissues ◽

Mammalian Tissues ◽

End Stage Heart Failure ◽

End Stage ◽

Oxide Synthase ◽

Endothelial Nitric Oxide

Nitric oxide (NO) is a potent endothelium-derived relaxing factor which also may modulate cardiomyocyte inotropism and growth via increasing cGMP. While endothelial nitric oxide synthase (eNOS) isoforms have been detected in non-human mammalian tissues, expression and localization of eNOS in the normal and failing human myocardium are poorly defined. Therefore, the present study was designed to investigate eNOS in human cardiac tissues in the presence and absence of congestive heart failure (CHF).Normal and failing atrial tissue were obtained from six cardiac donors and six end-stage heart failure patients undergoing primary cardiac transplantation. ENOS protein expression and localization was investigated utilizing Western blot analysis and immunohistochemical staining with the polyclonal rabbit antibody to eNOS (Transduction Laboratories, Lexington, Kentucky).

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Artificial cells containing sustainable energy conversion engines

Emerging Topics in Life Sciences ◽

10.1042/etls20190103 ◽

2019 ◽

Vol 3 (5) ◽

pp. 573-578 ◽

Cited By ~ 3

Author(s):

Kwanwoo Shin

Keyword(s):

Energy Conversion ◽

Nicotinamide Adenine Dinucleotide ◽

Sustainable Energy ◽

Living Cells ◽

Energy Transduction ◽

Artificial Cells ◽

Energy Conversion Process ◽

Metabolic Reactions ◽

Metabolic Activities ◽

Reduced Nicotinamide Adenine Dinucleotide

Living cells naturally maintain a variety of metabolic reactions via energy conversion mechanisms that are coupled to proton transfer across cell membranes, thereby producing energy-rich compounds. Until now, researchers have been unable to maintain continuous biochemical reactions in artificially engineered cells, mainly due to the lack of mechanisms that generate energy-rich resources, such as adenosine triphosphate (ATP) and reduced nicotinamide adenine dinucleotide (NADH). If these metabolic activities in artificial cells are to be sustained, reliable energy transduction strategies must be realized. In this perspective, this article discusses the development of an artificially engineered cell containing a sustainable energy conversion process.

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