UV‐inducible cellular aggregation of the hyperthermophilic archaeon Sulfolobus solfataricus is mediated by pili formation

• Published in: Molecular microbiology 2008-11, Vol.70 (4), p.938-952
• Main Authors: Fröls, Sabrina, Ajon, Malgorzata, Wagner, Michaela, Teichmann, Daniela, Zolghadr, Behnam, Folea, Mihaela, Boekema, Egbert J., Driessen, Arnold J. M., Schleper, Christa, Albers, Sonja‐Verena
• Format: Article
• Language: English
• Subjects: Adenosine triphosphatase; Adenosine Triphosphatases - genetics; Adenosine Triphosphatases - metabolism; Archaeal Proteins - genetics; Archaeal Proteins - metabolism; Bacteriology; Biological and medical sciences; Cells; Deoxyribonucleic acid; DNA; DNA Breaks, Double-Stranded - radiation effects; DNA Repair; DNA, Archaeal - genetics; Electron microscopes; Escherichia coli - genetics; Escherichia coli - metabolism; Escherichia coli - radiation effects; Flagella - genetics; Flagella - metabolism; Fundamental and applied biological sciences. Psychology; Gene Deletion; Gene Expression Regulation, Archaeal; Gene Knockout Techniques; Genes; Genes, Archaeal; Microbiology; Miscellaneous; Multigene Family; Mutation; Operon; Plasmids; Proteins; RNA, Archaeal - genetics; Stress, Physiological; Sulfolobus solfataricus; Sulfolobus solfataricus - genetics; Sulfolobus solfataricus - metabolism; Sulfolobus solfataricus - physiology; Sulfolobus solfataricus - radiation effects; Ultraviolet radiation; Ultraviolet Rays
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/j.1365-2958.2008.06459.x

Summary The hyperthermophilic archaeon Sulfolobus solfataricus has been shown to exhibit a complex transcriptional response to UV irradiation involving 55 genes. Among the strongest UV‐induced genes was a putative pili biogenesis operon encoding a potential secretion ATPase, two pre‐pilins, a putative transmembrane protein and a protein of unknown function. Electron microscopy and image reconstruction of UV‐treated cells showed straight pili with 10 nm in diameter, variable in length, not bundled or polarized and composed of three evenly spaced helices, thereby clearly being distinguishable from archaeal flagella. A deletion mutant of SSO0120, the central type II/IV secretion ATPase, did not produce pili. It could be complemented by reintroducing the gene on a plasmid vector. We have named the operon ups operon for UV‐inducible pili operon of Sulfolobus. Overexpression of the pre‐pilins, Ups‐A/B (SSO0117/0118) in Sulfolobus resulted in production of extremely long filaments. Pronounced cellular aggregation was observed and quantified upon UV treatment. This aggregation was a UV‐dose‐dependent, dynamic process, not inducible by other physical stressors (such as pH or temperature shift) but stimulated by chemically induced double‐strand breaks in DNA. We hypothesize that pili formation and subsequent cellular aggregation enhance DNA transfer among Sulfolobus cells to provide increased repair of damaged DNA via homologous recombination.