# Freimoser:Research

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## Research

The focus of the research in our group is a simple molecule: inorganic polyphosphate (poly P). Poly P is a linear polymer that consists of a variable number of phosphate residues (from three to more than a thousand) that are linked by energy-rich phosphoanhydride bonds. It has been detected in all organisms and living cells and was found in many organelles. In eukaryotes, poly P is particularly prominent in fungi, algae and trypanosomatids. Poly P serves as a phosphate and energy store and regulates enzymes, chromatin condensation and translation. Poly P is also involved in bacterial pathogenicity, survival during stationary phase in bacteria and yeast, or the adaptation to alkaline and osmotic stress. In the slime mold Dictyostelium discoideum, poly P regulates development and predation behaviour, and in humans blood coagulation is accelerated and fibrinolysis is delayed by poly P.

### Poly P in Saccharomyces cerevisiae:

We have developed a fast and easy method for the quantification of poly P in yeast, which is amenable for large-scale analyses. This allowed extraction and quantification of poly P in mutant strains of all non-essential yeast genes. From this screen we conclude that at least 5% of all yeast genes are required for the maintenance of normal poly P levels. We are now studying specific pathways to determine their link with poly P metabolism. In addition, we study phenotypical differences in poly P hypo- and hyper-accumulating strains in order to learn more about the biological significance of poly P accumulation in yeast.

### Cell wall localized poly P:

One of our major goals and a very difficult problem is the specific localization of poly P. We have developed a staining method that is based on poly P binding proteins and immunohistochemical detection that allows for highly sensitive localization of poly P in fungal cell walls. We have used this technique for a systematic study of poly P in fungi from all fungal phyla. In the future we will also define procedures to stain poly P intracellularly.