Effect of Hydrogen, Sucrose and Oxygen on Uptake Hydrogenase in Nitrogen-fixing and Ammonium-grown Pseudomonas saccharophila ATCC 15946

Barraquio, Wilfredo L.; Knowles, Roger

doi:10.1099/00221287-134-4-893

“…latus [172] and P. saccharophila [134]. Enzyme synthesis is repressed by high concentrations of organic substrates also in these two species.…”

Section: H Oxidation and Chemolithotrophymentioning

confidence: 95%

“…DNA topology has been suggested to regulate hydrogenase synthesis [170] based on the repression of hydrogenase expression when DNA gyrase inhibitors were added to the derepression medium [171]. 02 represses hydrogenase synthesis in Alcaligenes latus [172], Azospirillum brasilense [173,174] and Pseudomonas saccharophila [134]. Hydrogenase activities of A. brasilense [174] and A. lipoferum [173,175] are inhibited by 02, whereas those of A. amazonense [173] and P. saccharophila [134] are not.…”

Section: H Oxidation and Chemolithotrophymentioning

confidence: 99%

“…02 represses hydrogenase synthesis in Alcaligenes latus [172], Azospirillum brasilense [173,174] and Pseudomonas saccharophila [134]. Hydrogenase activities of A. brasilense [174] and A. lipoferum [173,175] are inhibited by 02, whereas those of A. amazonense [173] and P. saccharophila [134] are not. H 2 induces the synthesis of hydrogenase in A. latus [172], P. saccharophila [134] and X. autotrophicus [162], while that of hydrogenase in A. brasilense appears not inducible [174].…”

Section: H Oxidation and Chemolithotrophymentioning

confidence: 99%

“…Hydrogenase activities of A. brasilense [174] and A. lipoferum [173,175] are inhibited by 02, whereas those of A. amazonense [173] and P. saccharophila [134] are not. H 2 induces the synthesis of hydrogenase in A. latus [172], P. saccharophila [134] and X. autotrophicus [162], while that of hydrogenase in A. brasilense appears not inducible [174]. The H 2 evolved during N 2 fixation is most likely responsible for stimulating hydrogenase expression in A.…”

Section: H Oxidation and Chemolithotrophymentioning

confidence: 99%

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N2-fixing pseudomonads and related soil bacteria

Chan

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1994

FEMS Microbiology Reviews

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Pseudomonas-like organisms form a highly heterogeneous and ubiquitous group of bacteria. Recent identification of an authentic P~eudomonas genus should help to decrease difficulties which arose from taxonomic uncertainties. Further difficulties in recognising N2-fixing Pseudomonas species lie in the confirmation of diazotrophy. Optimised conditions are often needed for the detection of nitrogenase activity since it is controlled by specific environmental factors and physiological requirements. However, genetically constructed N2-fixing strains from authentic Pseudomonas species have demonstrated that at least some members of the genus possess mechanisms to accommodate and express nil (N z fixation) genes from a well-studied diazotroph, Klebsiella pneumoniae. Renowned for their catabolic versatility, pseudomonads can use a wide range of carbon and energy substrates. Hence, potential N2-fixing pseudomonads are conceivably less limited by carbon and energy sources available in the environment compared to other N2-fixing organisms. Pseudomonas species dominate in the rhizosphere of some plants from which isolates have been shown to be diazotrophic. Several strains are also chemolithotrophs, capable of using H 2 as energy and electron source and CO2 as carbon source. Besides assays for N2-fixing activity, DNA hybridisation to the well conserved molybdo-nitrogenase structural gene probe is an indicator of diazotrophy. However, absence of hybridisation to this probe, despite N 2 fixation activity, has been reported. Although the genetics of N 2 fixation in pseudomonads have hardly been studied, some nif genes have been shown to be plasmid-borne. Pseudomonas species are also predominant soil denitrifiers, reducing nitrate and nitrite to gaseous forms of nitrogen during anaerobic respiration. Hence, they play an important role in the global biological nitrogen cycle. Several diazotrophic species including a few pseudomonads can also denitrify. The potential contribution by Ne-fixing pseudomonads to the sinks and sources of soil nitrogen is considered small in the short term but essentially remains unclear in the absence of experimental data. Reliable rapid methods for their specific enumeration are indispensable for assessing their population dynamics and ascertaining their ecological significance.

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“…N 2 fixation by free-living aerobic heterotrophs occurs under microaerobic to aerobic conditions. Like most aerobic N 2 fixers, diazotrophic pseudomonads are microaerophilic when fixing N 2 [38,39,46,47,63,92,114,116,134]. In natural environments, soil moisture may indirectly influence nitrogenase activity by affecting 0 2 movement into the soil pores.…”

Section: Limiting Factorsmentioning

confidence: 99%

N₂-fixing pseudomonads and related soil bacteria

Chan

¹

,

Barraquio

²

,

Knowles

³

1994

FEMS Microbiology Reviews

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Pseudomonas-like organisms form a highly heterogeneous and ubiquitous group of bacteria. Recent identification of an authentic P~eudomonas genus should help to decrease difficulties which arose from taxonomic uncertainties. Further difficulties in recognising N2-fixing Pseudomonas species lie in the confirmation of diazotrophy. Optimised conditions are often needed for the detection of nitrogenase activity since it is controlled by specific environmental factors and physiological requirements. However, genetically constructed N2-fixing strains from authentic Pseudomonas species have demonstrated that at least some members of the genus possess mechanisms to accommodate and express nil (N z fixation) genes from a well-studied diazotroph, Klebsiella pneumoniae. Renowned for their catabolic versatility, pseudomonads can use a wide range of carbon and energy substrates. Hence, potential N2-fixing pseudomonads are conceivably less limited by carbon and energy sources available in the environment compared to other N2-fixing organisms. Pseudomonas species dominate in the rhizosphere of some plants from which isolates have been shown to be diazotrophic. Several strains are also chemolithotrophs, capable of using H 2 as energy and electron source and CO2 as carbon source. Besides assays for N2-fixing activity, DNA hybridisation to the well conserved molybdo-nitrogenase structural gene probe is an indicator of diazotrophy. However, absence of hybridisation to this probe, despite N 2 fixation activity, has been reported. Although the genetics of N 2 fixation in pseudomonads have hardly been studied, some nif genes have been shown to be plasmid-borne. Pseudomonas species are also predominant soil denitrifiers, reducing nitrate and nitrite to gaseous forms of nitrogen during anaerobic respiration. Hence, they play an important role in the global biological nitrogen cycle. Several diazotrophic species including a few pseudomonads can also denitrify. The potential contribution by Ne-fixing pseudomonads to the sinks and sources of soil nitrogen is considered small in the short term but essentially remains unclear in the absence of experimental data. Reliable rapid methods for their specific enumeration are indispensable for assessing their population dynamics and ascertaining their ecological significance. NUM347(a mbds.nrc.ca. distributed within any one genus, diazotrophic strains commonly exist in the genera of both archaeobacteria (eqv. archaebacteria [1]) and eubacteria. Free-living diazotrophs excluding photosynthetic bacteria and cyanobacteria are mostly heterotrophs with aerobic, microaerobic or anaerobic respiration when fixing N 2. Because of the high energy demand for N 2 fixation, free-liv-SSDI 01 68-6445(93)E0092-X

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pH dependence of uptake hydrogenases inAzospirillum brasilenseandA. amazonense

Fu

¹

,

Tito

²

,

Knowles

³

1989

FEMS Microbiology Letters

2

0

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Methylene blue (MB)‐dependent uptake hydrogenase activity of Azospirillum brasilense was at least 30% higher than O2‐dependent activity in this species, whereas for A. amazonense the reverse was true. Both MB‐dependent and O2‐dependent uptake hydrogenase activities of A. brasilense showed maxima at pH 7.0 both in vivo and in vitro. For A. amazonense, both in vivo and in vitro, the MB‐dependent uptake hydrogenase activity increased roughly linearly as pH values were increased from pH 6.25 to 7.75, whereas the O2‐dependent activity was almost unaffected by pH. The optimal pH for A. amazonense growth was broad and in the range of 5.4 to 6.5.

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Effect of Hydrogen, Sucrose and Oxygen on Uptake Hydrogenase in Nitrogen-fixing and Ammonium-grown Pseudomonas saccharophila ATCC 15946

Cited by 4 publications

References 27 publications

N2-fixing pseudomonads and related soil bacteria

N2-fixing pseudomonads and related soil bacteria

N₂-fixing pseudomonads and related soil bacteria

pH dependence of uptake hydrogenases inAzospirillum brasilenseandA. amazonense

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