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Applied and Environmental Microbiology, April 2004, p. 2137-2145, Vol. 70, No. 4
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.4.2137-2145.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Gas Exchange in the Filamentous Cyanobacterium Nostoc punctiforme Strain ATCC 29133 and Its Hydrogenase-Deficient Mutant Strain NHM5

Pia Lindberg,1,{dagger} Peter Lindblad,1* and Laurent Cournac2

Department of Physiological Botany, Evolutionary Biology Centre, Commissariat à l’Energie Atomique (CEA), Uppsala University, SE-752 36 Uppsala, Sweden,1 Direction des Sciences du Vivant, Département d’Ecophysiologie Végétale et de Microbiologie, Cadarache, DSV, DEVM, Laboratoire d'Ecophysiologie de la Photosynthèse, UMR 6191 CNRS CEA, Université Méditerranée CEA 1000, F-13108 Saint Paul lez Durance Cedex,France2

Received 11 August 2003/ Accepted 18 December 2003

Nostoc punctiforme ATCC 29133 is a nitrogen-fixing, heterocystous cyanobacterium of symbiotic origin. During nitrogen fixation, it produces molecular hydrogen (H2), which is recaptured by an uptake hydrogenase. Gas exchange in cultures of N. punctiforme ATCC 29133 and its hydrogenase-free mutant strain NHM5 was studied. Exchange of O2, CO2, N2, and H2 was followed simultaneously with a mass spectrometer in cultures grown under nitrogen-fixing conditions. Isotopic tracing was used to separate evolution and uptake of CO2 and O2. The amount of H2 produced per molecule of N2 fixed was found to vary with light conditions, high light giving a greater increase in H2 production than N2 fixation. The ratio under low light and high light was approximately 1.4 and 6.1 molecules of H2 produced per molecule of N2 fixed, respectively. Incubation under high light for a longer time, until the culture was depleted of CO2, caused a decrease in the nitrogen fixation rate. At the same time, hydrogen production in the hydrogenase-deficient strain was increased from an initial rate of approximately 6 µmol (mg of chlorophyll a)–1 h–1 to 9 µmol (mg of chlorophyll a)–1 h–1 after about 50 min. A light-stimulated hydrogen-deuterium exchange activity stemming from the nitrogenase was observed in the two strains. The present findings are important for understanding this nitrogenase-based system, aiming at photobiological hydrogen production, as we have identified the conditions under which the energy flow through the nitrogenase can be directed towards hydrogen production rather than nitrogen fixation.

* Corresponding author. Mailing address: Department of Physiological Botany, EBC, Uppsala University, SE-752 36 Uppsala, Sweden. Phone and fax: 46 18 4712826. E-mail: peter.lindblad{at}ebc.uu.se.

{dagger} Present address: Service de Bioénergétique, Dép. de Biologie Joliot Curie, CEA Saclay, 91191 Gif-Sur-Yvette Cedex, France.

Applied and Environmental Microbiology, April 2004, p. 2137-2145, Vol. 70, No. 4
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.4.2137-2145.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.



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