极端寄生虫的进化史

Extreme adaptations of species often cause such significant changes that their evolutionary¹ history is difficult to reconstruct. Zoologists² at the University of Basel in Switzerland have now discovered a new parasite³ species that represents the missing link between fungi⁴ and an extreme group of parasites⁵. Researches are now able to understand for the first time the evolution of these parasites, causing disease in humans and animals. The study has been published in the latest issue of the scientific journal Proceedings⁶ of the National Academy of Sciences (PNAS). Parasites use their hosts to simplify their own lives. In order to do so, they evolved features that are so extreme that it is often impossible to compare them to other species. The evolution of these extreme adaptations is often impossible to reconstruct. The research group lead by Prof. Dieter Ebert from the Department of Environmental Science at the University of Basel has now discovered the missing link that explains how this large group of extreme parasites, the microsporidia, has evolved. The team was supported in their efforts by scientists from Sweden and the U.S.   Microsporidia are a large group of extreme parasites that invade humans and animals and cost great damage for health care systems and in agriculture; over 1,200 species are known. They live inside their host's cells and have highly specialized⁷ features: They are only able to reproduce inside the host's cells, they have the smallest known genome of all organisms with a cell nucleus⁸ (eukaryotes) and they posses no mitochondria of their own (the cell's power plant). In addition, they developed a specialized infection apparatus⁹, the polar tube, which they use to insert themselves into the cells of their host. Due to their phenomenal high molecular¹⁰ evolution rate, genome analysis has so far been rather unsuccessful: Their great genomic divergence¹¹ from all other known organisms further complicates¹² the study of their evolutionary lineage.