Growth and septation of animal-attached bacteria

Up to now, the study of bacterial reproduction focused on a handful of model microorganisms. On the other hand, cell biological studies of environmental bacteria such as those thriving on animal surfaces are scarce. In this research proposal we want to determine the molecular and cell biological mechanisms underlying the reproductive anomalies of four Gammaproteobacteria stably associated to animals. The ultimate goal is the identification of cell growth and septum positioning mechanisms conserved among this ecologically and medically important group of microorganisms. We will study selected cell division proteins in cell-free systems and apply a wide palette of state-of-the-art and classic microscopic techniques to both live and fixed nematode-bacteria consortia (e.g. Selective Plane Illumination Microscopy, 3D structured illumination microscopy, cryo-EM and confocal laser scanning microscopy).

Project leader: Dr. Silvia Bulgheresi

Participants: Silvia Bulgheresi, Philipp Weber, Nika Pende, Lena König, Tobias Viehböck
Key collaborators:
Ass. Prof. Tanneke den Blaauwen, Swammerdam Institute for Life Sciences, Amsterdam, ·
Ass. Prof. Martin Loose, Institute of Science and Technology Austria (IST Austria), Klosterneuburg
Dr. Kareem Elsayad, Campus Science Support Facilities (CSF), Advanced Microscopy Facility, Vienna
Ass. Prof. Martin Pilhofer, ETH Zürich Department of Biology Institute of Molecular Biology & Biophysics, Zürich
Prof. Yves Brun & Prof. Michael Van Nieuwenhze, Indiana University

Duration: 01.11.2015-31.10.2020 

Funding agency: Austrian Science Fund (FWF)


Project completed

Bacterial cell growth and division have only been studied in a dozen of cultivable species in spite of the fact that millions of them are estimated to live on our planet. This knowledge gap must be urgently filled if we want to grasp the conserved fundamentals of cell reproduction. Therefore, we studied the reproductive strategies of Thiosymbion, a group of non-model bacteria, which exclusively occur on the surface of animals (ectosymbionts). In particular, in longitudinally dividing Thyiosymbion, we found that: 1) septation can start at one cell pole only, so that a ring of the tubulin homolog FtsZ is dispensable; 2) not only bacterial cell division but also cell growth can be host-polarised; 3) the actin homolog MreB is medial throughout the cell cycle and its polymerisation is required for medial FtsZ polymerisation and septation; 4) a bidimensional segregation mode maintains symbiont chromosome orientation toward it host. We hypothesise that these extraordinary cell biological features are adaptions to the symbiotic lifestyle. Establishment of symbiont cultures and development of gene manipulation/protein imaging techniques are ongoing to prove that cell biological adaptations, such as longitudinal division or fixed chromosome configuration, are required for symbiosis establishment or maintenance.

Publications from this project:

Pende N, Wang J, Weber P, Verheul J, Kuru E, Rittmann S..... Bulgheresi S, (2018). Host-Polarized Cell Growth in Animal Symbionts.. Current biology : CB, 28 (7), pp. 1039-1051.e5
DOI: 10.1016/j.cub.2018.02.028

Weber P, Moessel F, Paredes G, Viehboeck T, Vischer N, Bulgheresi S, (2019). A Bidimensional Segregation Mode Maintains Symbiont Chromosome Orientation toward Its Host.. Current biology : CB, 29 (18), pp. 3018-3028.e4
DOI: 10.1016/j.cub.2019.07.064

Leisch N, Pende N, Weber PM, Gruber-Vodicka HR, Verheul J, Vischer NO, Abby SS... Bulgheresi S. (2016). Asynchronous division by non-ring FtsZ in the gammaproteobacterial symbiont of Robbea hypermnestra.. Nature microbiology, pp. 16182
DOI: 10.1038/nmicrobiol.2016.182