The extracellular proteome of Sulfolobus

PhD ceremony: Mr. A.F. Ellen, 16.15 uur, Aula Academiegebouw, Broerstraat 5, Groningen

Dissertation: The extracellular proteome of Sulfolobus

Promotor(s): prof. A.J.M. Driessen

Faculty: Mathematics and Natural Sciences

Microorganisms secrete proteins in their environment that fulfill numerous functions. I made an inventory of the extracellular proteins in a group of microorganisms, called Sulfolobus, which live at 80°C and under acidic conditions. As it turns out Sulfolobus secretes relatively little protein into their environment. However, I discovered that vesicles that are released into their surrounding by Sulfolobus are associated with so-called ESCRT proteins. In higher organisms the ESCRT proteins are involved in cell division but they also play a role in creating vesicles in a cellular organel that is called the endosome. My research suggests that the roles of the ESCRT proteins are similar in Sulfolobus and higher organisms. I also discovered that two Sulfolbus species produce antimicrobial compounds that in the case of the species Sulfolobus tokodaii are associated with the extracellular vesicles. The identity of the antimicrobial compounds was previously not known in Sulfolobus but I discover the two proteins that are responsible for the antimicrobial activity. Both proteins are required for antimicrobial activity and they seem to represent a completely new group of antimicrobial proteins. Which of those two proteins is the actual antimicrobial protein remains to be discovered.