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

Abstract

SummaryThe 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.

Lrs14 transcriptional regulators influence biofilm formation and cell motility of Crenarchaea

“…However, none of the surface structure components, with the exception of upsAE, were found to be significantly altered in expression in biofilms formed by Dsaci1223 (Figure 4a). Although ups pili are essential for ultraviolet-induced cell aggregation and DNA transfer (Frö ls et al 2008), their role in surface attachment from shaking cultures and during biofilm maturation was demonstrated (Henche et al, 2011). However, Dups strains formed very unstable biofilms showing cell clusters unevenly distributed, which is different from Dsaci1223 biofilms.…”

Tackling the minority: sulfate-reducing bacteria in an archaea-dominated subsurface biofilm

“…By placing an in situ trapping system in this subsurface setting, slime-like biofilm structures consisting almost exclusively of SM1 euryarchaeal cells can be caught from the water stream, in stark contrast to the abovementioned string-of-pearls community (Henneberger et al, 2006). This second life-style of the SM1 Euryarchaeon differs also from other described microbial systems, in which archaea are involved in biofilm formation (Lapaglia and Hartzell, 1997;Tyson et al, 2004;Frols et al, 2008): first, the SM1 euryarchaeal biofilm represents the only known naturally occurring Archaea-dominated biofilm, revealing a purity of up to 95% based on microscopic counts (Henneberger et al, 2006). Second, the small archaeal cocci form porous colonies with defined distances between the single cells mediated by their unique cell surface appendages (Moissl et al, 2005;Henneberger et al, 2006).…”

Type IV Pilin Proteins: Versatile Molecular Modules

“…In many species, surface contact-or, perhaps, a local increase in viscosity or mechanical strain on membranes-leads to upregulation of pilin expression (43). In Haemophilus influenzae, alkaline pH is required for optimal pilus expression (33), while some archaea produce T4P in response to UV irradiation (7,147). For many pathogens, T4P are made only in response to growth under specific culture conditions or at specific temperatures and/or in response to host cell contact (102,254,274).…”