Current Research Interests and Cooperations
Research activities in the Molecular Bioenergetics Group at the Institute of Physical Chemistry, University of Vienna, has always been and still is focusing on cyanobacteria
(blue-green algae). Special interest is thereby paid to respiratory electron transport and energy conversion (ATP synthesis), interactions between photosynthesis and respiration,
and to enzymes responsible for the scavenging (detoxification) of reactive oxygen species (ROS). Major achievements our research group has made over the past years on these three aspects of cyanobacterial bioenergetics were the identification and characterization of a fully functional terminal respiratory oxidase in both cytoplasmic or plasma membranes (CM) and intracytoplasmic or thylakoid membranes (ICM) of at present thirty-three different species and strains of cyanobacteria as an aa3-type cytochrome-c oxidase, the identification of the plastoquinol-cytochrome-c/plastocyanin electron transport sequence as the common link of respiratory and photosynthetic electron transport in cyanobacterial thylakoid membranes, and the isolation, purification, and functional & genetic characterization of a cytosolic bifunctional cyanobacterial catalase ("catalase-peroxidase"). A major breakthrough achieved in our group, independently of but at about the same time as in Norio Murata’s group in Okazaki, was the successful isolation, separation and purification of fully functional CM and ICM from a wide variety of cyanobacteria. In this way it could be shown, rather unexpectedly, that also the chlorophyll-free CM was the site of a complete respiratory chain including the aa3-type cytochrome-c oxidase. Attempts are currently made in cooperation with the group of Prof. Shelagh Ferguson-Miller at the MSU in East Lansing, USA, to overexpress this enzyme in Rhodobacter sphaeroides in order to finally obtain sufficient amounts of the enzyme for in-depth kinetic and spectroscopic studies. A further point of recent interest which has come from the release of the totally sequenced genomes of Synechocystis sp. PCC6803 - and quite recently also of Anabaena sp.PCC7120- are questions related to the possible occurrence of three different terminal respiratory oxidases in cyanobacteria according to three different sets of oxidase genes that were identified, but of which only the aa3-type cytochrome-c oxidase has been found so far to be expressed under a variety of different growth conditions checked. And a final aspect of more recent research in our group(s) is the monofunctional (i.e. "classical") catalase that was isolated here from Chlorogloeopsis fritschii and has turned out to be the only monofunctional catalase among >20 cyanobacterial species screened for the presence of superoxide dismutases and various types of hydroperoxidases.
Our traditional cyanobacteria on which we have obtained most our major results published so far and which continue to be used for most basic bioenergetic investigations in our laboratory are Anacystis nidulans (Synechococcus sp. PCC6301), Synechocystis sp. PCC6803, Anabaena (Nostoc) sp. PCC7120 and 7939, and Nostoc sp. PCC8009.