Initially working on evolutionary topics, we are now interested in the molecular mechanisms emerging when secondary evolved organisms originated. Here, a eukaryotic cell was engulfed by a host cell and the compartments of the symbiont were either reduced or eliminated. In the species we are working with at the moment, the symbiont was minimized to a plastid (complex plastid), which is surrounded by four membranes.
One topic of our recent work is the identification and characterization of the components and mechanisms, necessary to transport proteins across the four plastid surrounding membranes. Meanwhile we have identified the major players and the basic mechanisms involved in protein transport across the second and third outermost membrane.
A further project deals with a bacterial endosymbiont of a diatom. Here we are interested in the functions as well as in the genomic sequence of the endosymbiont.
Within SYNMIKRO we are working on two topics:
A: Diatoms as bioreactors
B: Genomic adaptations to intracellular lifestyle
A: There is a huge economical interest in the biotechnological production of molecules valuable for industrial and medical applications. Bacteria, fungi as well as mammalian cell cultures are used as bioreactors and more recently plants are of high interest for biotechnological syntheses as well. In order to run a bioreactor efficiently, not only the production rates but also the production costs are important issues. Bacteria, fungi and cell cultures need for their cultivation carbohydrates, which are an important cost factor. Plants on the other hand are light driven and synthesize their own energy-rich molecules. However, cultivation of plants as bioreactors depends on agricultural areas, which competes with food production.
Diatoms are unicellular organisms combining many useful characters for biotechnological production. They are light driven as plants, easy and cheap to propagate and need for cultivation no agricultural areas. The aim of our project is to establish diatoms as bioreactors. For that we use techniques to manipulate the organisms in the way that they produce molecules of our interest. In the meantime we were able to produce biopolymers as well as molecules of medical interest in the diatom. The production rates are promising, indicating that diatoms are bioreactors with a very high potential.
B: Internalization and intracellular reduction of symbionts within host cells are naturally occurring systems, in which the adaptation of symbiontic genomes to intracellular lifestyle can be studied. It is known that intracellular symbionts show in comparison to free-living relatives losses of cellular capacities and therefore losses of the encoding genes, making them to naturally minimized systems highlighting essential functions. In that respect, we are studying symbionts of bacterial and eukaryotic origin.
The most prominent compartments of eukaryotic cells, which originated via bacterial symbioses are the plastids, the mitochondria and the organelles of mitochondrial origin. Plastids and mitochondria harbor genomes, which are highly reduced due to gene losses and gene transfers into the cell nucleus of the host. We are studying the genomes of mitochondria and plastids in respect to similarities in gene content, which might indicate that some genes cannot be transferred into the cell nucleus. These have to be expressed in organello in a regulated manner. In addition, the evolution of plastids is studied by investigating genomic adaptations in the transition of a free-living cyanobacterium, the ancestors of these organelles, to plastids of land plants and algae.
Some algal groups originated by the fusion of two eukaryotic cells. In the course of co-evolution, the symbiont of many taxa, a photosynthetic active eukaryotic alga, was reduced to a plastid including a remnant cytoplasm, the PPC. We are determining the proteome of phylogenetic different PPCs. In a combined in silico/in vivo approach we investigate the functions and molecular players of the PPC, with the aim to extract essential functions in a naturally minimized eukaryotic system.