NDLI: Hydrogen production by nitrogenase as a potential crop rotation benefit

Please wait, while we are loading the content...

Hydrogen production by nitrogenase as a potential crop rotation benefit

Content Provider	Springer Nature Link
Author	Golding, Amber Leigh Dong, Zhongmin
Copyright Year	2010
Abstract	Both climate change and the adverse effects of chemical use on human and environmental health are recognized as serious issues of global concern. Nowhere is this more apparent than in the agricultural sector where release of greenhouse gases such as carbon dioxide, nitrous oxide and methane continues to be problematic and where use of nitrogen fertilizer is responsible for negative impacts on both human populations and ecosystems. The manipulation of biological nitrogen fixation (BNF) could help alleviate part of the difficulty by decreasing the need for nitrogen fertilizers, which require huge quantities of fossil fuel to produce and contribute to the release of nitrous oxide from soil as well as being responsible for the contamination of drinking water systems and natural habitats. BNF is performed by a variety of microorganisms. One of the most studied examples is the BNF carried out by rhizobial bacteria in symbiosis with their plant hosts such as pea and soybean. Hydrogen gas is an energy-rich, obligate by-product of BNF. Legume symbioses with rhizobia lacking hydrogenase enzymes (which can recycle hydrogen) have traditionally been viewed as energetically inefficient. However, recent studies suggest hydrogen release to soil may be beneficial, increasing soil carbon sequestration and promoting growth of hydrogen-oxidizing bacteria beneficial to plant growth; the alleged superiority of symbiotic performance in rhizobia possessing functional hydrogenases (HUP+) over those rhizobia without functional hydrogenases (HUP−) has also not been conclusively shown. The structure of the iron-molybdenum cofactor or FeMo-co of nitrogenase (the active site of the enzyme) has been elucidated through X-ray crystallography but the mechanism of nitrogen fixation remains unknown. However, studies of effects of hydrogen production on BNF have revealed potential candidate intermediates involved in the nitrogenase reaction pathway and have also shown the role of hydrogen as a competitive inhibitor of N2, with hydrogen now considered to be the primary regulator of the nitrogenase electron allocation coefficient. The regulation of oxygen levels within legume root nodules is also being investigated; nitrogen fixation is energetically expensive, requiring a plentiful oxygen supply but too high an oxygen concentration can irreversibly damage nitrogenase, so some regulation is needed. There is evidence from gas diffusion studies suggesting the presence of a diffusion barrier in nodules; leghaemoglobin is another potential O2 regulator. Possible functions of hydrogenases include hydrogen recycling, protection of nitrogenase from damaging O2 levels and prevention of inhibitory H2 accumulation; there is evidence for H2 recycling only in studies where H2 uptake has been strongly coupled to ATP production and where this is not the case, it is believed that the hydrogenase acts as an O2 scavenger, lowering O2 concentrations. The distribution of hydrogenases in temperate legumes has been found to be narrow and root and shoot grafting experiments suggest the host plant may exert some influence on the expression of hydrogenase (HUP) genes in rhizobia that possess them. Many still believe that HUP+ rhizobia are superior in performance to HUP− species; to this end, many attempts to increase the relative efficiency of nitrogenase through the introduction of HUP genes into the plasmids or chromosomes of HUP− rhizobia have been carried out and some have met with success but many other studies have not revealed an increase in symbiotic performance after successful insertion of HUP genes so the role of HUP in increasing parameters such as N2 fixation and plant yield is still unclear. One advantage of the hydrogen production innate to BNF is that the H2 evolved can be used to measure N2 fixation using new open-flow gas chamber techniques seen as superior to the traditional acetylene reduction assay (ARA) conducted in closed chambers, although H2 cannot be used for field studies yet as the ARA can. However, the ARA is now believed to be unreliable in field studies and it is recommended that other measures such as dry weight, yield and total nitrogen content are more accurate, especially in determining real food production, particularly in the developing nations. Another potential benefit of H2 release from root nodules is that it stays in the soil and has been found to be consumed by H2-oxidizing bacteria, many of which show plant growth–promoting properties such as the inhibition of ethylene biosynthesis in the host plant, leading to root elongation and increased plant growth; they may well be promising as biofertilizers if they can be successfully developed into seed inoculants for non-leguminous crop species, decreasing the need for chemical fertilizers. It has been suggested that rhizobia can produce nitrous oxide through denitrification but this has never been shown; it is possible that hydrogen release may provide more ideal conditions for denitrifying, free-living bacteria and so increase production of nitrous oxide that way and this issue will require more study. However, it seems unlikely that a natural system would release nitrous oxide to the same degree that chemical fertilizers have been shown to do.
Starting Page	101
Ending Page	121
Page Count	21
File Format	PDF
ISSN	16103653
Journal	Environmental Chemistry Letters
Volume Number	8
Issue Number	2
e-ISSN	16103661
Language	English
Publisher	Springer-Verlag
Publisher Date	2010-03-12
Publisher Place	Berlin, Heidelberg
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Geochemistry Analytical Chemistry Pollution Environmental Chemistry Ecotoxicology
Content Type	Text
Resource Type	Article
Subject	Environmental Chemistry

Sl.	Authority	Responsibilities	Communication Details
1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
2	Indian Institute of Technology Kharagpur	Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project	https://www.iitkgp.ac.in
3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
5	Website/Portal (Helpdesk)	Queries regarding NDLI and its services	support@ndl.gov.in
6	Contents and Copyright Issues	Queries related to content curation and copyright issues	content@ndl.gov.in
7	National Digital Library of India Club (NDLI Club)	Queries related to NDLI Club formation, support, user awareness program, seminar/symposium, collaboration, social media, promotion, and outreach	clubsupport@ndl.gov.in
8	Digital Preservation Centre (DPC)	Assistance with digitizing and archiving copyright-free printed books	dpc@ndl.gov.in
9	IDR Setup or Support	Queries related to establishment and support of Institutional Digital Repository (IDR) and IDR workshops	idr@ndl.gov.in

Pollution history revealed by sedimentary records: a review

Humic substances as surfactants

Efficient hydrogen peroxide decomposition to oxygen and water catalysed by a ruthenium pincer complex

Influence of support on catalytic behavior of nickel catalysts in the steam reforming of ethanol for hydrogen production

Nanosilver products and toxicity

Environmental geochemistry of technetium

Microbes to clean indoor pollutants

Electrochemistry: as cause and cure in water pollution—an overview

Soil irrigation with toxic cyanobacterial microcystins increases soil nitrification potential

Hydrogen production by nitrogenase as a potential crop rotation benefit

Similar Documents

Pollution history revealed by sedimentary records: a review

Humic substances as surfactants

Efficient hydrogen peroxide decomposition to oxygen and water catalysed by a ruthenium pincer complex

Influence of support on catalytic behavior of nickel catalysts in the steam reforming of ethanol for hydrogen production

Nanosilver products and toxicity

Environmental geochemistry of technetium

Microbes to clean indoor pollutants

Electrochemistry: as cause and cure in water pollution—an overview

Soil irrigation with toxic cyanobacterial microcystins increases soil nitrification potential

Hydrogen production by nitrogenase as a potential crop rotation benefit