Failure of Putative Nitrogen-fixing Bacteria to Fix Nitrogen

Hill, Susan; Postgate, J. R.

doi:10.1099/00221287-58-2-277

Cited by 91 publications

(37 citation statements)

References 9 publications

(3 reference statements)

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“…To verify that these organisms did indeed possess nitrogenase and that the observed growth was not due to scavenging of trace amounts of fixed nitrogen present in medium (see Hill & Postgate, 1969), the acetylene reduction test was done on each culture. Cells from flasks grown at their optimum p02 values were injected into assay flasks and re-gassed to the required p 0 2 values.…”

Section: Results a N D Discussionmentioning

confidence: 99%

Nitrogen Fixation in Obligate Methanotrophs

Murrell

Dalton

1983

Microbiology

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A number of representative species of obligate methane-oxidizing bacteria were surveyed for their ability to fix N2 by growth experiments and the acetylene reduction test. Although all strains exhibited growth on nitrogen-free plates, only type I1 organisms and the type X methanotroph Methylococcus capsulatus (Bath) grew well in nitrogen-free liquid medium and were capable of active acetylene reduction. N,-fixation in type I1 methanotrophs was less sensitive to 0, than in the type X methanotroph Methylococcus capsulatus (Bath) and batch cultures of type I1 organisms could be established at p 0 2 values of up to 0.2 bar. N,-fixation in Methylococcus capsulatus (Bath) was inhibited at p 0 2 values above 0.1 5 bar and the 'switch-off' of nitrogenase activity by ammonia was also observed in this organism.

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Section: Results a N D Discussionmentioning

confidence: 99%

Nitrogen Fixation in Obligate Methanotrophs

Murrell

Dalton

1983

Microbiology

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“…Instead, the organisms must be able to survive using the traces of combined nitrogen in the media and in the air (Hill & Postgate, 1969) and the need to assess nitrogen fixation by means other than Kjeldahl has been discussed by these workers.…”

Section: Discussionmentioning

confidence: 99%

Non-symbiotic Nitrogen-fixing Organisms from Some New Zealand Tussock-grassland Soils

Line

Loutit

1971

Journal of General Microbiology

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SUMMARYThe screening of several hundred isolates from tussock-grassland soils for nitrogen-fixing ability resulted in the isolation of Clostridium butyricum and five facultatively anaerobic nitrogen-fixing species. These latter have been identified as Bacillus circulans (tentative identification), B. polymyxa, Enterobacter aerogenes (formerly Aerobucter aerogenes), Klebsiella pneumoniae and Escherichia intermedia.Estimates of numbers of these species indicate that they will be responsible for only very low rates of nitrogen fixation in the soils tested.

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“…The ability of the pseudomonads to fix atmospheric N 2 has not been appreciated [7,66,67] usually because of the following problems [39]: (a) mistaken or uncertain identification of the diazotroph; (b) lack of rigorous tests for diazotrophy in pseudomonads; and (c) multigeneric nature of the genus Pseudomonas as discussed above. Early attempts to find an N2-fixing pseudomonad were unsuccessful, due to the failure to recognise the 02 sensitivity or microaerobic character of its N2-fixing system.…”

Section: Diazotrophymentioning

confidence: 99%

“…Under such conditions, bacteria that fix N 2 microaerobically and prefer N-deficient media containing 'starter' nitrogen are likely to be missed. On the other hand, organisms which have the ability to scavenge traces of volatile nitrogenous compounds such as ammonia from the immediate atmosphere or organisms which could assimilate contaminating nitrogenous compounds in the medium could be misconstrued as Nz-fixing [66]. The test, however, is still useful in isolating putative N 2 fixers.…”

Section: Determinative Testsmentioning

confidence: 99%

N2-fixing pseudomonads and related soil bacteria

Chan

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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Failure of Putative Nitrogen-fixing Bacteria to Fix Nitrogen

Cited by 91 publications

References 9 publications

Nitrogen Fixation in Obligate Methanotrophs

Nitrogen Fixation in Obligate Methanotrophs

Non-symbiotic Nitrogen-fixing Organisms from Some New Zealand Tussock-grassland Soils

N2-fixing pseudomonads and related soil bacteria

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