Dissertation: "Expression and synthetic activation of [FeFe]-hydrogenases in cyanobacteria"

  • Date:
  • Location: Zoom Polhemsalen (It will be possible to follow the dissertation through Zoom.)
  • Doctoral student: Adam Wegelius
  • About the dissertation
  • Organiser: Department of Chemistry - Ångström Laboratory
  • Contact person: Peter Lindblad
  • Phone: 018-471 2826
  • Disputation

Adam Wegelius defends his PhD thesis entitled "Expression and synthetic activation of [FeFe]-hydrogenases in cyanobacteria".

Opponent: Prof. Matthew Posewitz, Department of Chemistry, Colorado School of Mines, USA

Supervisors: Prof. Peter Lindblad, Associate Professor Karin Stensjö, and Dr. Namita Khanna, Department of Chemistry - Ångström, Molecular Biomimetics, Uppsala

Please note that due to restrictions, a very limited number of spectators will be able to follow the event on site. It will therefore be possible to follow the dissertation via Zoom. Contact the lecturer or tutor to access the zoom link before the event.

Link to the thesis in full text in DiVA.

Abstract

Photosynthetic microbes can be utilized for hydrogen production, generating a clean, carbon neutral energy carrier from abundant substrates. Cyanobacteria are photosynthetic prokaryotes with large potential for biotechnological energy applications and several strains are capable of hydrogen production. This production is catalysed by a bi-directional [NiFe]-hydrogenase, or by nitrogenase during nitrogen fixation. However, nature’s foremost hydrogen producing enzymes, the [FeFe]-hydrogenases, are not present in these organisms. Many [FeFe]-hydrogenases boast incredible catalytic activities and high bias towards proton reduction. Introduction of a suitable [FeFe]-hydrogenase in a cyanobacterial host could greatly improve the hydrogen production capacity. Unfortunately, generation and characterisation of cyanobacterial strains carrying active [FeFe]-hydrogenases is stalled by the intricate maturation process associated with these enzymes.

In this thesis, I investigate heterologous expression and artificial maturation of [FeFe]-hydrogenases in cyanobacteria. Genetic tools to reliably express [FeFe]-hydrogenases were developed and tested in the unicellular cyanobacterium Synechocystis PCC 6083, and in heterocysts of the filamentous cyanobacterium Nostoc punctiforme ATCC 29133. Following heterologous expression, functional, semisynthetic [FeFe]-hydrognases operating in vivo in cyanobacterial cells were generated by synthetic activation. The procedure proved successful in both the unicellular and filamentous strain, and for [FeFe]-hydrogenases from different groups and subclasses. The semisynthetic enzymes proved capable of hydrogen production under different environmental conditions and links to the metabolism of the host cell. Hydrogen production capacity proved long-lived and was retained for several days. In Nostoc punctiforme, synthetic activation was confirmed to generate active [FeFe]-hydrogenase in both vegetative cells and heterocyst.

The results presented in this thesis demonstrate a novel way to explore in vivo hydrogen production from heterologous [FeFe]-hydrogenases in cyanobacteria. In the search for suitable candidates for H2 production systems, synthetic activation may be used to investigate a wide range of [FeFe]-hydrogenases, strains and cultivation conditions, circumventing the need of elaborate maturation machinery optimisation.