High-Affinity Vanadate Transport System in the Cyanobacterium<i>Anabaena variabilis</i>ATCC 29413

Pratte, Brenda S.; Thiel, Teresa

doi:10.1128/jb.188.2.464-468.2006

Cited by 32 publications

(43 citation statements)

References 58 publications

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“…RNAs were isolated from 50-ml cultures grown in AA/8, with or without fructose, and subjected to DNase digestion using a Turbo DNA-free kit (Ambion). Reverse transcription-PCR (RT-PCR) was performed as previously described (34), with the following change: 2.5 ng of RNA and 2.5 U of Superscript III (Invitrogen) were added per reaction. Primers were annealed at 58°C.…”

Section: Methodsmentioning

confidence: 99%

Regulation of Fructose Transport and Its Effect on Fructose Toxicity in Anabaena spp

2008

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Anabaena variabilis grows heterotrophically using fructose, while the close relative Anabaena sp. strain PCC 7120 does not. Introduction of a cluster of genes encoding a putative ABC transporter, herein named frtRABC, into Anabaena sp. strain PCC 7120 on a replicating plasmid allowed that strain to grow in the dark using fructose, indicating that these genes are necessary and sufficient for heterotrophic growth. FrtR, a putative LacI-like regulatory protein, was essential for heterotrophic growth of both cyanobacterial strains. Transcriptional analysis revealed that the transport system was induced by fructose and that in the absence of FrtR, frtA was very highly expressed, with or without fructose. In the frtR mutant, fructose uptake was immediate, in contrast to that in the wild-type strain, which required about 40 min for induction of transport. In the frtR mutant, high-level expression of the fructose transporter resulted in cells that were extremely sensitive to fructose. Even in the presence of the inducer, fructose, expression of frtA was low in the wild-type strain compared to that in the frtR mutant, indicating that FrtR repressed the transporter genes even in the presence of fructose. FrtR bound to the upstream region of frtA, but binding was not visibly altered by fructose, further supporting the hypothesis that fructose has only a modest effect in relieving repression of frtA by FrtR. A. variabilis grew better with increasing concentrations of fructose up to 50 mM, showing increased cell size and heterocyst frequency. Anabaena sp. strain PCC 7120 did not show any of these changes when it was grown with fructose. Thus, although Anabaena sp. strain PCC 7120 could take up fructose and use it in the dark, fructose did not improve growth in the light.

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Section: Methodsmentioning

confidence: 99%

Regulation of Fructose Transport and Its Effect on Fructose Toxicity in Anabaena spp

2008

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“…What happens to V in the periplasmic space of A. vinelandii is not known, but the catechols azotochelin and protochelin have been shown to be involved in Mo uptake as well as V uptake (Bellenger et al, unpublished), and molybdate in the periplasm is transported by a well-characterized ABC-type transporter (19,23,28). Such transporters commonly are used for oxoanion uptake (21,28,30,32), and one recently was identified for vanadate transport in A. variabilis (27). If such a transport system also exists in A. vinelandii, V uptake may be very similar to Mo uptake.…”

Section: Discussionmentioning

confidence: 99%

“…There are few studies of V uptake in microorganisms, but recently a high-affinity uptake system for vanadate was found in the N 2 -fixing cyanobacterium Anabaena variabilis (27). This system is an ABC-type transporter similar to those used for Mo uptake in various prokaryotes, including A. vinelandii (25).…”

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Vanadium Requirements and Uptake Kinetics in the Dinitrogen-Fixing Bacterium Azotobacter vinelandii

Bellenger

Wichard

Kraepiel

2008

Appl Environ Microbiol

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Vanadium is a cofactor in the alternative V-nitrogenase that is expressed by some N 2 -fixing bacteria when Mo is not available. We investigated the V requirements, the kinetics of V uptake, and the production of catechol compounds across a range of concentrations of vanadium in diazotrophic cultures of the soil bacterium Azotobacter vinelandii. In strain CA11.70, a mutant that expresses only the V-nitrogenase, V concentrations in the medium between 10 ؊8 and 10 ؊6 M sustain maximum growth rates; they are limiting below this range and toxic above. A. vinelandii excretes in its growth medium micromolar concentrations of the catechol siderophores azotochelin and protochelin, which bind the vanadate oxoanion. The production of catechols increases when V concentrations become toxic. Short-term uptake experiments with the radioactive isotope 49 V show that bacteria take up the V-catechol complexes through a regulated transport system(s), which shuts down at high V concentrations. The modulation of the excretion of catechols and of the uptake of the V-catechol complexes allows A. vinelandii to precisely manage its V homeostasis over a range of V concentrations, from limiting to toxic.

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“…The Mo-repressed vnf genes in A. variabilis are not tightly clustered but are found within a region of about 40 kb, which includes many uncharacterized genes (7). In addition to the structural genes, vnfH, vnfDG, and vnfK, there are the genes for scaffolding proteins, vnfEN, and the vanadate transport genes, vupABC (32,33).…”

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Role of RNA Secondary Structure and Processing in Stability of the nifH1 Transcript in the Cyanobacterium Anabaena variabilis

2015

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In the cyanobacterium Anabaena variabilis ATCC 29413, aerobic nitrogen fixation occurs in micro-oxic cells called heterocysts. Synthesis of nitrogenase in heterocysts requires expression of the large nif1 gene cluster, which is primarily under the control of the promoter for the first gene, nifB1. Strong expression of nifH1 requires the nifB1 promoter but is also controlled by RNA processing, which leads to increased nifH1 transcript stability. The processing of the primary nifH1 transcript occurs at the base of a predicted stem-loop structure that is conserved in many heterocystous cyanobacteria. Mutations that changed the predicted secondary structure or changed the sequence of the stem-loop had detrimental effects on the amount of nifH1 transcript, with mutations that altered or destabilized the structure having the strongest effect. Just upstream from the transcriptional processing site for nifH1 was the promoter for a small antisense RNA, sava4870.1. This RNA was more strongly expressed in cells grown in the presence of fixed nitrogen and was downregulated in cells 24 h after nitrogen step down. A mutant strain lacking the promoter for sava4870.1 showed delayed nitrogen fixation; however, that phenotype might have resulted from an effect of the mutation on the processing of the nifH1 transcript. The nifH1 transcript was the most abundant and most stable nif1 transcript, while nifD1 and nifK1, just downstream of nifH1, were present in much smaller amounts and were less stable. The nifD1 and nifK1 transcripts were also processed at sites just upstream of nifD1 and nifK1. IMPORTANCEIn the filamentous cyanobacterium Anabaena variabilis, the nif1 cluster, encoding the primary Mo nitrogenase, functions under aerobic growth conditions in specialized cells called heterocysts that develop in response to starvation for fixed nitrogen. The large cluster comprising more than a dozen nif1 genes is transcribed primarily from the promoter for the first gene, nifB1; however, this does not explain the large amount of transcript for the structural genes nifH1, nifD1, and nifK1, which are also under the control of the distant nifB1 promoter. Here, we demonstrate the importance of a predicted stem-loop structure upstream of nifH1 that controls the abundance of nifH1 transcript through transcript processing and stabilization and show that nifD1 and nifK1 transcripts are also controlled by transcript processing.A nabaena variabilis is a filamentous cyanobacterium that fixes nitrogen under oxic growth conditions in cells called heterocysts. Heterocysts, which are specialized micro-oxic cells that develop in a semiregular pattern in the filament in response to nitrogen stress, fix atmospheric dinitrogen to ammonium using the enzyme nitrogenase (1-3). The micro-oxic conditions of the heterocyst result from the glycolipid layer that may restrict oxygen diffusion into the cell, the absence of oxygen-evolving photosystem II, and increased respiration, all of which serve to protect nitrogenase from oxygen (4-6). While all heter...

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High-Affinity Vanadate Transport System in the CyanobacteriumAnabaena variabilisATCC 29413

Cited by 32 publications

References 58 publications

Regulation of Fructose Transport and Its Effect on Fructose Toxicity in Anabaena spp

Regulation of Fructose Transport and Its Effect on Fructose Toxicity in Anabaena spp

Vanadium Requirements and Uptake Kinetics in the Dinitrogen-Fixing Bacterium Azotobacter vinelandii

Role of RNA Secondary Structure and Processing in Stability of the nifH1 Transcript in the Cyanobacterium Anabaena variabilis

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