Our lab’s research places special emphasis on type IV pili, cell surface structures that mediate, and, in some cases, regulate, the processes involved in establishing and maintaining biofilms, microbial aggregates that allow cells to survive severe environmental stresses.
While investigating the roles played by pili in surface adhesion, we discovered six conserved H. volcanii adhesion pilins are also involved in regulating flagella-dependent motility. This previously unknown mechanism that plays a role in mediating the transition from the planktonic to sessile state, underscores the importance of the ability to quickly adapt to severe changes in the local environment. Complementation experiments indicate that pilin regulation of motility does not require assembled pili and that pilins do not interact directly with the flagella. We are now attempting to identify an intermediate through which pilin-dependent motility regulation operates (Fig. 3).
Surprisingly, while some type IV pilins promote microcolony formation, as has previously been reported, a distinct subset inhibits this early step in biofilm formation. Preliminary quantitative mass spectrometry analyses carried out in collaboration with the Hippler lab at the Wilhelms University of Muenster suggest differential expression of pilins in planktonic and early biofilm cells. We are also investigating the effects that N-glycosylation, as well as other post-translation modifications, have on this regulatory mechanism in collaboration with the Hippler lab.
These biochemical and molecular biological characterizations are complemented by transposon screens for mutants exhibiting an adhesion phenotype, using an H. volcanii transposon library we recently developed in collaboration with the Savilathi lab at the University of Turku.
- Legerme G., E. Yang, R. Esquivel, S. Kiljunan, H. Savilathi and M. Pohlschroder. 2016. Screening of a Haloferax volcanii transposon library reveals novel motility and adhesion mutants. Life.6:1-14.
- Esquivel, R., S. Schulze, M. Hippler and M. Pohlschroder. 2016. Identification of Haloferax volcanii flagellin and pilin N-glycans with diverse roles. J. Biol. Chem. 291:10602-14.
- Pohlschroder, M. and S. Albers. 2016. Editorial: Archaeal cell envelope and surface structures. Front. Microbiol. 6:1515.
- Pohlschroder, M. and R. Esquivel. 2015. Archaeal type IV pili and their roles in biofilm formation. Frontiers in Microbiology (invited review).6:190.
- Kiljunen, S., M. Pujunen, K. Dilks, S. Storf, M. Pohlschroder and H. Savilahti. 2014. Generation of comprehensive transposon insertion mutant library for the model archaeon, Haloferax volcanii, and its use for gene discovery. BMC Biol. 103.
- Esquivel R. and M. Pohlschroder. 2014. A conserved type IV pilin signal peptide H-domain is critical for the post-translational regulation of flagella-dependent motility. Mol. Microbiol. 93:493-504.
- Esquivel, R, R. Xu and M. Pohlschroder. 2013. Novel, archaeal adhesion pilins with a conserved N-terminus. J. Bacteriol. 195:3808-3818.
- Tripepi, M., R. Esquivel and M. Pohlschroder. 2013. Haloferax volcanii cells lacking the flagellin, FlgA2, are hypermotile. Microbiol. 159:2249-2258.
- Tripepi, M., J. You, S. Temel, O. Onder, D. Brisson, and M. Pohlschroder. 2012. N-glycosylation of Haloferax volcanii flagellins is essential for flagella-biosynthesis. J. Bacteriol. 194:4876-4887.
- Szabo, Z. and M. Pohlschroder. 2012. Diversity and subcellular distribution of archaeal secreted proteins. Invited review. Front. in Microbiol. doi: 10.3389/fmicb. 00207.
- Imam S., Z. Chen, D.S. Roos, and M. Pohlschroder. 2011. Identification of surprisingly diverse type IV Pili, across a broad range of gram-positive bacteria. PloS One 6(12):e28919.
- Pohlschroder, M., A. Ghosh, M. Tripepi, and S. Albers. 2011. Archaeal type IV pilus-like structures – ancient prokaryotic surface organelles. Invited Review. Curr. Opin. in Microbiol. 4(3):357-63.