Abstract
A series of Rhizobium meliloti and Rhizobium trifolii strains were used as inocula for alfalfa and clover, respectively, grown under bacteriologically controlled conditions. Replicate samples of nodules formed by each strain were assayed for rates of H(2) evolution in air, rates of H(2) evolution under Ar and O(2), and rates of C(2)H(2) reduction. Nodules formed by all strains of R. meliloti and R. trifolii on their respective hosts lost at least 17% of the electron flow through nitrogenase as evolved H(2). The mean loss from alfalfa nodules formed by 19 R. meliloti strains was 25%, and the mean loss from clover nodules formed by seven R. trifolii strains was 35%. R. meliloti and R. trifolii strains also were cultured under conditions that were previously established for derepression of hydrogenase synthesis. Only strains 102F65 and 102F51 of R. meliloti showed measurable activity under free-living conditions. Bacteroids from nodules formed by the two strains showing hydrogenase activity under free-living conditions also oxidized H(2) at low rates. The specific activity of hydrogenase in bacteroids formed by either strain 102F65 or strain 102F51 of R. meliloti was less than 0.1% of the specific activity of the hydrogenase system in bacteroids formed by H(2) uptake-positive Rhizobium japonicum USDA 110, which has been investigated previously. R. meliloti and R. trifolii strains tested possessed insufficient hydrogenase to recycle a substantial proportion of the H(2) evolved from the nitrogenase reaction in nodules of their hosts. Additional research is needed, therefore, to develop strains of R. meliloti and R. trifolii that possess an adequate H(2)-recycling system.
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Claims 9
Claim · model-written summary
Nodules formed by R. meliloti on alfalfa lost at least 17% of nitrogenase electron flow as hydrogen.
- Taxon
- alfalfa
Medicago sativae1 - Organ / stage
- Nodulese0
- Interactor
- R. meliloti
Sinorhizobium melilotie0symbiont - Outcome
- electron flow through nitrogenase as evolved H(2)e0
- Direction
- loste0
- Value
- at least 17%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nodules formed by all strains of R. meliloti and R. trifolii on their respective hosts lost at least 17% of the electron flow through nitrogenase as evolved H(2)”
e1“inocula for alfalfa and clover, respectively”
Claim · model-written summary
Nodules formed by R. trifolii on clover lost at least 17% of nitrogenase electron flow as hydrogen.
- Organ / stage
- Nodulese0
- Interactor
- R. trifolii
Rhizobium leguminosarume0symbiont - Outcome
- electron flow through nitrogenase as evolved H(2)e0
- Direction
- loste0
- Value
- at least 17%e0
TrifoliumOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nodules formed by all strains of R. meliloti and R. trifolii on their respective hosts lost at least 17% of the electron flow through nitrogenase as evolved H(2)”
e1“inocula for alfalfa and clover, respectively”
Claim · model-written summary
Alfalfa nodules formed by 19 R. meliloti strains lost a mean 25% of electron flow as hydrogen.
- Taxon
- alfalfaMedicago sativae0
- Organ / stage
- nodulese0
- Interactor
- R. melilotiSinorhizobium melilotie0symbiont
- Outcome
- mean losse0
- Value
- 25%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The mean loss from alfalfa nodules formed by 19 R. meliloti strains was 25%”
Claim · model-written summary
Clover nodules formed by seven R. trifolii strains lost a mean 35% of electron flow as hydrogen.
- Organ / stage
- nodulese0
- Interactor
- R. trifoliiRhizobium leguminosarume0symbiont
- Outcome
- mean losse0
- Value
- 35%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the mean loss from clover nodules formed by seven R. trifolii strains was 35%”
Claim · model-written summary
Only R. meliloti strains 102F65 and 102F51 showed measurable hydrogenase activity while free living.
- Material
- strains 102F65 and 102F51e0
- Interactor
- R. melilotiSinorhizobium melilotie0symbiont
- Outcome
- measurable activitye0
Not reportedTaxon
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Only strains 102F65 and 102F51 of R. meliloti showed measurable activity under free-living conditions”
Claim · model-written summary
Bacteroids from those two strains oxidized hydrogen at low rates.
- Organ / stage
- nodulese0
- Interactor
- R. melilotiSinorhizobium melilotie1symbiont
- Outcome
- oxidized H(2)e0
- Qualifier
- at low ratese0
Not reportedTaxon
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Bacteroids from nodules formed by the two strains showing hydrogenase activity under free-living conditions also oxidized H(2) at low rates”
e1“strains 102F65 and 102F51 of R. meliloti”
Claim · model-written summary
Hydrogenase activity in bacteroids of the two R. meliloti strains was below 0.1% of the R. japonicum comparator.
- Interactor
- R. melilotiSinorhizobium melilotie0symbiont
- Outcome
- specific activity of hydrogenasee0
- Direction
- less thane0
- Value
- 0.1%e0
- Comparator
- Rhizobium japonicum USDA 110e0
Not reportedTaxon
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The specific activity of hydrogenase in bacteroids formed by either strain 102F65 or strain 102F51 of R. meliloti was less than 0.1% of the specific activity of the hydrogenase system in bacteroids formed by H(2) uptake-positive Rhizobium japonicum USDA 110”
Claim · model-written summary
The tested rhizobia had insufficient hydrogenase to recycle much of the hydrogen evolved from host nodules.
- Interactor
- R. melilotiSinorhizobium melilotie0symbiont
- Gene
- hydrogenasee0
- Outcome
- recycle a substantial proportion of the H(2)e0
Not reportedTaxon
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“R. meliloti and R. trifolii strains tested possessed insufficient hydrogenase to recycle a substantial proportion of the H(2) evolved from the nitrogenase reaction in nodules of their hosts”
Claim · model-written summary
The authors call for developing rhizobial strains with adequate hydrogen recycling.
- Outcome
- develop strains of R. meliloti and R. trifolii that possess an adequate H(2)-recycling systeme0
Not reportedTaxon
Verbatim
e0“Additional research is needed, therefore, to develop strains of R. meliloti and R. trifolii that possess an adequate H(2)-recycling system”