Identification of hox genes and analysis of their transcription in the unicellular cyanobacterium Gloeocapsa alpicola CALU 743 growing under nitrate-limiting conditions

Abstract

The unicellular non-N 2 -fixing cyanobacterium Gloeocapsa alpicola CALU 743 contains a bidirectional hydrogenase. Parts of all structural genes, encoding the hydrogenase, were identified, cloned and sequenced. When comparing the sequences with analogous sequences from other cyanobacteria the highest similarity was observed with hox genes from Synechocystis sp. PCC 6803. The hydrogenase activity increased considerably when the cells were grown aerobically in a medium with limiting concentrations of nitrate. However, the relative abundances of hoxH and hoxY transcripts, detected by RT-PCR, did not change significantly, demonstrating that the increase in the activity of G. alpicola hydrogenase was not a result of the increase of the transcription. In contrast, in Anabaena variabilis the induction of a bidirectional hydrogenase activity correlated with the relative level of hoxH and hoxY transcripts. ß : S 0 3 7 8 -1 0 9 7 ( 0 2 ) 0 0 8 9 4 -7

Transcription and Regulation of the Bidirectional Hydrogenase in the Cyanobacterium Nostoc sp. Strain PCC 7120

“…Anaerobic induction of the two hox gene clusters. It has been demonstrated that anaerobic conditions induce higher transcription levels of hoxH transcript in the filamentous, heterocystous Nostoc muscorum and Anabaena variabilis ATCC 29413 (6,46). In the present study, when cells of Nostoc sp.…”

“…3), a result which is in agreement with physiological data reported earlier (19,20). It has long been demonstrated that microaerobic/ anaerobic conditions influence the bidirectional hydrogenase activity in heterocystous cyanobacteria (6,19,20,39,44,46). However, this is the first time that it is demonstrated that the anaerobically induced activity of the enzyme is in parallel with an increase in transcription of the two hox operons in Nostoc sp.…”

“…Relatively little is known about the transcriptional regulation of the bidirectional hydrogenase in cyanobacteria. The relative abundances of hoxY and hoxH transcript levels in Gleocapsa alpicola did not change significantly under nitrogen-limiting conditions (46), while the activity of the enzyme increased considerably (46,51). The hoxH transcript level was not affected by a shift from ammonium-grown cells to N 2 -fixing conditions or the addition of hydrogen for Nostoc muscorum (6,7).…”

Characterization and transcriptional analysis of hupSLW in Gloeothece sp. ATCC 27152: an uptake hydrogenase from a unicellular cyanobacterium

“…In addition, a bi-directional enzyme (encoded by hoxEFUYH) may be present which, depending on the growth conditions, may display the capacity of both producing and consuming H 2 (Lambert & Smith, 1981;Houchins, 1984;Schmitz et al, 2002;Tamagnini et al, 2002). All cyanobacteria examined so far contain an uptake, a bi-directional or both the hydrogenases (Schmitz et al, 1995(Schmitz et al, , 2002Boison et al, 1996;Tamagnini et al, 2000Tamagnini et al, , 2002Sheremetieva et al, 2002;Schütz et al, 2004). Moreover, the uptake-type enzyme has been found in all nitrogen fixing cyanobacterial strains studied to date (Carrasco & Golden, 1995;Oxelfelt et al, 1998;Happe et al, 2000;Tamagnini et al, 2000Tamagnini et al, , 2002Schütz et al, 2004).…”

Redirecting Reductant Flux into Hydrogen Production via Metabolic Engineering of Fermentative Carbon Metabolism in a Cyanobacterium

“…Lactate was found to be the major excreted fermentation product of wild-type (WT) cells, and the enzyme producing D-lactate, which competes with hydrogenase for reducing equivalents, was eliminated genetically. Nitrate deprivation (25) and nickel supplementation (3) were previously shown to increase hydrogen yield in other strains, and therefore these treatments were examined in combination with the ldhA mutation to optimize conditions for hydrogen production. The ldhA mutant has dramatically redistributed fermentative fluxes in comparison to WT cells and a higher NAD(P)H/NAD(P) ϩ ratio and up to 5-fold higher hydrogen production than those of WT cells.…”