Excision of an 11-kilobase-pair DNA element from within the nifD gene in anabaena variabilis heterocysts

Brusca, John S.; Hale, Michael A.; Carrasco, Claudio D.; Golden, James W.

doi:10.1128/jb.171.8.4138-4145.1989

Cited by 53 publications

(40 citation statements)

References 41 publications

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“…The excisase gene xisA is located on the excised DNA element. This gene rearrangement occurs in heterocystous cyanobacteria, such as the best-studied species Anabaena variabilis (37) and Anabaena (Nostoc) PCC 7120 (43), but not in nonheterocystous, N 2 -fixing forms (93). Similar rearrangements happen during the late stages of heterocyst development of some cyanobacteria.…”

Section: Occurrence Of Nitrogenases In Heterocystsmentioning

confidence: 85%

Nitrogen Fixation and Hydrogen Metabolism in Cyanobacteria

Bothe

Schmitz²,

Yates

et al. 2010

Microbiol Mol Biol Rev

357

222

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SUMMARY This review summarizes recent aspects of (di)nitrogen fixation and (di)hydrogen metabolism, with emphasis on cyanobacteria. These organisms possess several types of the enzyme complexes catalyzing N2 fixation and/or H2 formation or oxidation, namely, two Mo nitrogenases, a V nitrogenase, and two hydrogenases. The two cyanobacterial Ni hydrogenases are differentiated as either uptake or bidirectional hydrogenases. The different forms of both the nitrogenases and hydrogenases are encoded by different sets of genes, and their organization on the chromosome can vary from one cyanobacterium to another. Factors regulating the expression of these genes are emerging from recent studies. New ideas on the potential physiological and ecological roles of nitrogenases and hydrogenases are presented. There is a renewed interest in exploiting cyanobacteria in solar energy conversion programs to generate H2 as a source of combustible energy. To enhance the rates of H2 production, the emphasis perhaps needs not to be on more efficient hydrogenases and nitrogenases or on the transfer of foreign enzymes into cyanobacteria. A likely better strategy is to exploit the use of radiant solar energy by the photosynthetic electron transport system to enhance the rates of H2 formation and so improve the chances of utilizing cyanobacteria as a source for the generation of clean energy.

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Section: Occurrence Of Nitrogenases In Heterocystsmentioning

confidence: 85%

Nitrogen Fixation and Hydrogen Metabolism in Cyanobacteria

Bothe

Schmitz²,

Yates

et al. 2010

Microbiol Mol Biol Rev

357

222

View full text Add to dashboard Cite

show abstract

“…The nifB gene of Anabaena sp. strain PCC 7120 was used as a probe of restriction digests of chromosomal DNA from A. variabilis ATCC 29413 and of cosmid 33D12, which contains the nif region of A. variabilis (9,24), to identify the approximate location of nifB (data not shown).…”

Section: Resultsmentioning

confidence: 99%

“…The nif genes of A. variabilis ATCC 29413 that are the homologs of the nif genes of Anabaena sp. strain PCC 7120 have been cloned and mapped (24), and the 11-kb excision element, but not the 55-kb excision element, has been found in that nif cluster (9).…”

mentioning

confidence: 99%

Characterization of nifB, nifS, and nifU genes in the cyanobacterium Anabaena variabilis: NifB is required for the vanadium-dependent nitrogenase

Lyons

Thiel

1995

J Bacteriol

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Anabaena variabilis ATCC 29413 is a heterotrophic, nitrogen-fixing cyanobacterium containing both a Mo-dependent nitrogenase encoded by the nif genes and V-dependent nitrogenase encoded by the vnf genes. The nifB, nifS, and nifU genes of A. variabilis were cloned, mapped, and partially sequenced. The fdxN gene was between nifB and nifS. Growth and acetylene reduction assays using wild-type and mutant strains indicated that the nifB product (NifB) was required for nitrogen fixation not only by the enzyme encoded by the nif genes but also by the enzyme encoded by the vnf genes. Neither NifS nor NifU was essential for nitrogen fixation in A. variabilis.Anabaena spp. are filamentous cyanobacteria capable of fixing dinitrogen in specialized morphologically distinct cells called heterocysts (18,41). Under diazotrophic growth conditions, vegetative cells compose 90 to 95% of the cells in a filament and contain both photosystems I and II. The other 5 to 10% of cells are heterocysts that have only photosystem I and therefore evolve no oxygen (40). Additional envelope layers in heterocysts may protect nitrogenase from oxygen (38, 39).Many nif genes have been identified in Anabaena sp. strain PCC 7120: one large cluster contains nifB, fdxN, nifS, nifU, nifH, nifD, nifK, nifN, nifX, open reading frame 3, nifW, open reading frame 1, open reading frame 2, and fdxH (8,23,30,33,36,37,42). nifJ is not part of the cluster (4). The nifB-fdxNnifS-nifU operon is interrupted by a 55-kb insertion in fdxN, and the nifD gene has an 11-kb insertion, both of which are excised during heterocyst differentiation (19,20). The heterocyst ferredoxin gene of Anabaena sp. strain PCC 7120, fdxH, is downstream of the other characterized nif genes in the cluster (8). The nif genes of A. variabilis ATCC 29413 that are the homologs of the nif genes of Anabaena sp. strain PCC 7120 have been cloned and mapped (24), and the 11-kb excision element, but not the 55-kb excision element, has been found in that nif cluster (9).Besides the nif genes that encode nitrogenase 1, which requires a Mo cofactor, Anabaena variabilis also contains vnf genes that encode nitrogenase 2, which requires a V cofactor (53). Nitrogenases that do not require Mo were first described in Azotobacter vinelandii, which has nitrogenase 1, nitrogenase 2, and nitrogenase 3. Nitrogenase 3, which requires only Fe in the cofactor, is encoded by the anf genes (6, 10, 27). The vnf and anf systems of A. vinelandii do not have homologs of all the genes of the nif system. Known vnf and anf genes include vnfDGK, homologous to nifDK; vnfEN, homologous to nifEN; vnfA, homologous to nifA; and anfHDGK, homologous to nif HDK (6). The nifB, nifS, nifU, nifM, and nifV genes are required for the activity of all three nitrogenases of A. vinelandii (28,29). The vnfEN genes may also function in the anf system (6). The vnf-and anf-encoded nitrogenases are repressed by Mo and have the ability to reduce acetylene not only to ethylene but also to ethane, which is one criterion for the presence of these altern...

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“…However, this particular nifH is not part of a nif-gene cluster in A. variabilis. This organism possesses three nifclusters, one of which is interrupted by an insertion sequence including an integrase (Brusca et al, 1989). Under anaerobic conditions, this insertion sequence is excised, leaving an intact nif operon that functions in vegetative cells (Thiel et al, 1995).…”

Section: Discussionmentioning

confidence: 99%

Horizontal transfer of the nitrogen fixation gene cluster in the cyanobacterium Microcoleus chthonoplastes

et al. 2009

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The filamentous, non-heterocystous cyanobacterium Microcoleus chthonoplastes is a cosmopolitan organism, known to build microbial mats in a variety of different environments. Although most of these cyanobacterial mats are known for their capacity to fix dinitrogen, M. chthonoplastes has not been assigned as a diazotrophic organism. None of the strains that were correctly identified as M. chthonoplastes has been shown to fix dinitrogen and it has repeatedly been reported that these organisms lacked the cyanobacterial nifH, the structural gene for dinitrogenase reductase. In this study, we show that a complete nif-gene cluster is present in the genome of M. chthonoplastes PCC 7420 and that the three structural nitrogenase genes, nifHDK, are present in a collection of axenic strains of M. chthonoplastes from distant locations. Phylogenetic analysis of nifHDK revealed that they cluster with the Deltaproteobacteria and that they are closely related to Desulfovibrio. The nif operon is flanked by typical cyanobacterial genes, suggesting that it is an integral part of the M. chthonoplastes genome. In this study, we provide evidence that the nif operon of M. chthonoplastes is acquired through horizontal gene transfer. Moreover, the presence of the same nif-cluster in M. chthonoplastes isolates derived from various sites around the world suggests that this horizontal gene transfer event must have occurred early in the evolution of M. chthonoplastes. We have been unable to express nitrogenase in cultures of M. chthonoplastes, but we show that these genes were expressed under natural conditions in the field.

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Excision of an 11-kilobase-pair DNA element from within the nifD gene in anabaena variabilis heterocysts

Cited by 53 publications

References 41 publications

Nitrogen Fixation and Hydrogen Metabolism in Cyanobacteria

Nitrogen Fixation and Hydrogen Metabolism in Cyanobacteria

Characterization of nifB, nifS, and nifU genes in the cyanobacterium Anabaena variabilis: NifB is required for the vanadium-dependent nitrogenase

Horizontal transfer of the nitrogen fixation gene cluster in the cyanobacterium Microcoleus chthonoplastes

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