Dr. Reinhard Wirth
Working area: Cell Surface Appendages of Archaea
Cell surface appendages of microorganisms may serve various functions like motility (flagella) or adhesion (fimbriae/pili). Some – but by far not all – surface appendages of bacteria are characterized very well; in case of the “standard motility organelle”, namely the flagellum of Escherichia coli we know e.g.: its structure and synthesis up to the molecular level, all genes involved and their hierarchic regulation, the function as rotating filament, the mechanism of stimulus recognition and processing etc. For at least two adhesion structures – fimbriae (also called pili) – we know their structure, their mode of synthesis etc.
In the case of archaea much less is known. It has been proven only for haloarchaea that their flagella rotate to result in swimming. It is speculated – but not proven – that archaeal flagella grow from the basis (in contrast to bacterial flagella); absolutely nothing is known with respect to the motor. A comparison of bacterial and archaeal flagella is shown in Fig. 1 (from Bardy et al., (2003) Microbiology 149:295-304). In case of archaeal fimbriae we know since 1979 only that they exist; no data, as to e.g. their function or composition, however, are available. In our group we started 4 years ago a systematic analysis of archaeal cell surface appendages, concentrating on a few species – since 2007 that work is supported by a joint DFG grant together with Dr. Reinhard Rachel (University of Regensburg). We are interested especially in the structure of cell surface appendages, their function (in vitro and in vivo), their mode of biosynthesis, etc. It turned out that we have identified in some cases new adhesins, which might be of technological interest.
Fig. 1: Schemes for function and synthesis of bacterial and archaeal flagella (Bardy et al., 2003; Microbiology 149:295-304).
Flagella of Pyrococcus furiosus
The main results here come from the ph.d. work (finished in 2007) of Daniela Näther. She was able to show that the motility organelles of this hyperthermophilic archaeum not only are used for swimming; the flagella have a diameter of ca. 10 nm and can be up to 8 µm long. [According to its name rushing fireball the cocci move very fast; we have no exact data as to their velocity, yet. For this we would need high-speed movies, which had to be taken with a “thermo-microscope”, requiring work under anaerobic conditions at the optimal growth temperature of 95° C.] D. Näther was able to show that P. furiosus uses its flagella also for adhesion to various surfaces; in addition flagella can be aggregated into “cable-like” structures to result in cell-cell-connections. In the course of this work (done in cooperation with Dr. R. Rachel, University of Regensburg, and Prof. Dr. Gerhard Wanner, University of Munich) we obtained very attractive pictures, used e.g. as cover of J. Bacteriol. (October, 2006); (Fig. 2: Adhesion of P. furiosus via flagella to a sand grain from its natural habitat and formation of cell-cell-contacts). Further (unpublished) work of D. Näther defined various transcripts of the flagellar operon; during that work we learned that the published genome sequence in that region contains major faults.
Fig. 2: Adhesion of P. furiosus to a sand grain from its habitat and formation of cell-cell-contacts
Cell Surface Appendages of Other Archaea
All data mentioned here (again obtained in cooperation with Dr. R. Rachel and Prof. Dr. G. Wanner) are unpublished and, therefore, given only in summary.
We have been able to show that the fimbriae of Methanothermobacter thermoautotrophicus are used for adhesion to various surfaces. We have identified the structural gene for the fimbrin and could express it as a fusion protein. Antibodies against the recombinant fimbrin react with the fimbriae, which are ca. 5.5 nm in diameter and up to 10 µm long. Fig. 3 shows a picture of cells plus fimbriae obtained by fluorescence staining (size bar 5 µm).
In the case of Ignicoccus hospitalis we have identified a new structure, arbitrarily called fibers. These are up to 20 µm long filaments of ca. 15 µm diameter, again (as for the M. thermoautotrophicus fimbriae) encoded by an unannotated gene. The main function seems to be adhesion; Fig. 4 shows cells with fibers grown on mica (size bar 5 µm).
A new methanogenic isolate (“KIN24-T80”) was characterized by Annett Bellack during her diploma thesis. The archaeum possesses even more flagella than P. furiosus; they are used for swimming, adhesion and formation of cell-cell-contacts. First data indicate that this isolate might be a very good model to study archaeal flagella. Fig. 5 demonstrates the multitude of flagella on KIN24-T80 cells (size bar 1 µm).
Interactions of Pyrococcus furiosus with Biotic Surfaces
Data obtained by D. Näther gave rise to the question if P. furiosus might be able to interact with biotic surfaces. In a first approach we used Methanopyrus kandleri, an archaeum found in similar biotopes like P. furiosus (sea water, close to 100° C, anaerobic conditions). During her diploma thesis Simone Schopf used the fact that P. furiosus is inhibited by its own fermentation product H2, which is used by M. kandleri for its energy-yielding reactions during methanogenesis. She was able to establish a stable coculture of these two archaeons, using a medium with a special gas phase. It turned out that M. kandleri does adhere to glass – in contrast to P. furiosus. P. furiosus, however, is able to adhere to M. kandleri cells (and to cells of its own species), resulting in a structured biofilm – often of fried egg appearance (Fig. 6 shows such a colony). Very interestingly, P. furiosus seems to interact with M. kandleri not only via its flagella, but is able to establish also direct cell-cell-connections (Fig. 7: early stadium of interaction between 4 single P. furiosus cocci with one M. kandleri rod).
|Before 2003 we worked on:|
|The possibility of gene transfer between archaea and bacteria (specifically Methanocaldococcus jannaschii and Thermotoga maritima) – supported by Bayerische Forschungsstiftung Projekt 171/96.|
|Bacteria from marine macroorganisms as producers of biologically active substances – supported by BMBF Projekt: "Endo- und exozytische Mikroorganismen aus marinen Makroorganismen: Eine Quelle für biologisch aktive Naturstoffe".|
|Specific bacterial pheromones, the so-called sex pheromones, of Enterococcus faecalis – supported by DFG Projekt Wi 731/6-1 und 6-2.|
|Prof. Dr. Reinhard Wirth||Raum BIO 1.01.21||Tel.: +49 941 943 1825||Fax.: +49 941 943 1824|
|Dr. Annett Bellack||Raum BIO 1.01.19||Tel.: +49 941 943 1828|
|Elke Papst, Techn. Assistentin||Raum BIO 1.01.19||Tel.: +49 941 943 1827|
|Elisabeth Piechatchek||Raum BIO 1.01.19||Tel.: +49 941 943 1827|
|Matthias Ugele||Raum BIO 1.01.19||Tel.: +49 941 943 1827|
Wirth, R., Muscholl, A., Wanner, G.: The role of pheromones in bacterial interactions. Trends Microbiol. 4:96-103 (1996)
Marcinek, H., Wirth, R., Muscholl, A., Gauer, M.: Enterococcus faecalis gene transfer under natural conditions in municipal sewage water treatment plants. Appl. Env. Microbiol. 64:626-632 (1998)
Baumann, C., Judex, M., Huber, H., Wirth, R.: Estimation of genome sizes of hyperthermophiles. Extremophiles 2:101-108 (1998)
Wirth, R.: Sex pheromones and gene transfer in Enterococcus faecalis. Res. Microbiol. 151:493-496 (2000)
Süßmuth, S., Muscholl, A., Wirth, R., Susa, M., Marre, R., Rozdzinski, E.: Aggregation Substance Promotes Adherence, Phagocytosis, and Intracellular Survival of Enterococcus faecalis within Human Macrophages and Suppresses Respiratory Burst. Infect. Immun. 68:4900-4906 (2000)
Waar, K., Muscholl-Silberhorn, A.B., Willems, R.J.L., Slooff, M.J.H., Harmsen, H.J.M., Degener, J.E.: Genogrouping and Incidence of Virulence Factors of Enterococcus faecalis in Liver Transplant Patients Differ from Blood Culture and Fecal Isolates. J. Infect. Dis. 185:1121-1127 (2002)
Siebert, K., M. Busl, I. Asmus, J. Freund, A. Muscholl-Silberhorn, and R. Wirth. Evaluation of Methods for Storage of Marine Macroorganisms with Optimal Recovery of Bacteria. Appl. Environ. Microbiol. 70 :5912-5915 (2004)
Näther, D.J.; R.
Rachel, G. Wanner, and R. Wirth. 2006. Flagella of Pyrococcus furiosus:
Multifunctional Organelles, Made for Swimming, Adhesion to Various Surfaces,
and Cell-Cell Contacts. J. Bacteriol. 188:6915-6923 (2006)
course in microbiology
# Advanced course organismic microbiology I
# Advanced course organismic microbiology II
# Research course in microbiology
# Final course in microbiology
# Lectures (2-years-rhythm):
microbial physiology II
bacterial mechanisms of pathogenicity