Species-specific recognition of Sulfolobales mediated by UV-inducible pili and S-layer glycosylation patterns

Abstract

AbstractThe UV-inducible pili system of Sulfolobales (Ups) mediates the formation of species-specific cellular aggregates. Within these aggregates, cells exchange DNA in order to repair DNA double strand breaks via homologous recombination. Substitution of theS. acidocaldariuspilin subunits UpsA and UpsB with their homologs fromSulfolobus tokodaiishowed that these subunits facilitate species-specific aggregation. A region of low conservation within the UpsA homologs is primarily important for this specificity. Aggregation assays in the presence of different sugars showed the importance ofN-glycosylation in the recognition process. In addition, theN-glycan decorating the S-layer ofS. tokodaiiis different from the one ofS. acidocaldarius. Therefore, eachSulfolobusspecies seems to have developed a unique UpsA binding pocket and uniqueN-glycan composition to ensure aggregation and consequently also DNA exchange with cells from only the same species, which is essential for DNA repair by homologous recombination.ImportanceType IV pili can be found on the cell surface of many archaea and bacteria where they play important roles in different processes. The Ups-pili from the crenarchaeal Sulfolobales species are essential in establishing species-specific mating partners, ensuring genome stability. With this work, we show that differentSulfolobusspecies have species-specific regions in their Ups-pilin subunits, which allow them to interact only with cells from the same species. Additionally, differentSulfolobusspecies all have unique S-layerN-glycosylation patterns. We propose that the unique features of each species allow the recognition of specific mating partners. This knowledge for the first time gives insights into the molecular basis of archaeal self-recognition.