Location of nitrogen fixation (nif) genes on indigenous plasmids of Enterobacter agglomerans

Singh, Mahavir; Kleeberger, A.; Klingmüller, Walter

doi:10.1007/bf00331061

Cited by 51 publications

(6 citation statements)

References 28 publications

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“…It is possible that the N 2 -fixing ability of IRBG500 is localized on extrachromosomal elements present. Such extrachromosomal nitrogenase has been detected in other enteric bacteria such as Enterobacter agglomerans (59) and Rahnella aquatilis (7). Although an expected fragment of 400 bp was amplified when the plasmid DNA was used as the template, it remains to be confirmed if the nitrogenase genes are localized on the plasmid because the plasmid DNA isolated also had contaminating genomic DNA (Fig.…”

Section: Discussionmentioning

confidence: 97%

Endophytic Colonization of Rice by a Diazotrophic Strain of Serratia marcescens

et al. 2001

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Six closely related N 2 -fixing bacterial strains were isolated from surface-sterilized roots and stems of four different rice varieties. The strains were identified as Serratia marcescens by 16S rRNA gene analysis. One strain, IRBG500, chosen for further analysis showed acetylene reduction activity (ARA) only when inoculated into media containing low levels of fixed nitrogen (yeast extract). Diazotrophy of IRBG500 was confirmed by measurement of 15 N 2 incorporation and by sequence analysis of the PCR-amplified fragment of nifH. To examine its interaction with rice, strain IRBG500 was marked with gusA fused to a constitutive promoter, and the marked strain was inoculated onto rice seedlings under axenic conditions. At 3 days after inoculation, the roots showed blue staining, which was most intense at the points of lateral root emergence and at the root tip. At 6 days, the blue precipitate also appeared in the leaves and stems. More detailed studies using light and transmission electron microscopy combined with immunogold labeling confirmed that IRBG500 was endophytically established within roots, stems, and leaves. Large numbers of bacteria were observed within intercellular spaces, senescing root cortical cells, aerenchyma, and xylem vessels. They were not observed within intact host cells. Inoculation of IRBG500 resulted in a significant increase in root length and root dry weight but not in total N content of rice variety IR72. The inoculated plants showed ARA, but only when external carbon (e.g., malate, succinate, or sucrose) was added to the rooting medium.

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Section: Discussionmentioning

confidence: 97%

Endophytic Colonization of Rice by a Diazotrophic Strain of Serratia marcescens

et al. 2001

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“…Since the nif genes of P. stutzeri CMT.9.A are plasmid-borne [38], they could have been lost through plasmid curing during routine subculturing. Plasmid-borne nif genes are known in diazotrophs of the genera Desulfol:ibrio [96], Enterobacter [99], Lignobacter [100], Rahnella [101] and Rhizobium [102]. As for JM300, the genomic location of its nif genes has not been investigated and its diazotrophy has yet to be confirmed by 15N 2 incorporation.…”

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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“…agglomerans 19-1-1 Nal r, Kmr/Nm r, a strain containing the nif plasmid pEA9 with Tn5-mob inserted in it as a label, and E. agglomerans 339 Sm r, a strain cured of its nif plasmid by heat treatment, were used for soil inoculations as described by Klingmiiller et al [1,2]. For a description of nil plasmids of E. agglomerans and the labelling procedure see Singh et al [3] and Klingmtiller et al [4]. A 3-kb sequence from the nil cluster of the pEA9 plasmid was isolated from pJJ3.0B (a derivative of pBR322) [5] and used as a probe for DNA-DNA hybridisation.…”

Section: Bacterial Strains Plasmids and Soil Inoculationsmentioning

confidence: 99%

Direct detection of nif-gene sequences of Enterobacter agglomerans in soil

Selenska

1991

FEMS Microbiology Letters

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Location of nitrogen fixation (nif) genes on indigenous plasmids of Enterobacter agglomerans

Cited by 51 publications

References 28 publications

Endophytic Colonization of Rice by a Diazotrophic Strain of Serratia marcescens

Endophytic Colonization of Rice by a Diazotrophic Strain of Serratia marcescens

N2-fixing pseudomonads and related soil bacteria

Direct detection of nif-gene sequences of Enterobacter agglomerans in soil

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