prereflexive cogito Fabian Czerwinski's blog


Focal adhesions in bacteria: PLOS Computational Biology accepts our paper

Dear Dr. Igoshin,

We are pleased to inform you that we will be delighted to publish your manuscript, 'Myxococcus xanthus gliding motors are elastically coupled to the substrate as predicted by the focal adhesion model of gliding motility', in PLOS Computational Biology.

to: Oleg A. Igoshin
cc: Rajesh Balagam, Douglas B. Litwin, Fabian Czerwinski, Mingzhai Sun, Heidi B. Kaplan, Joshua W. Shaevitz

What a great find in your inbox on a Friday morning! Oleg had taken the lead in taking the debate about the gliding motility of Myxococcus xanthus to a new level. Myxo, this soil-dwelling 2um-long bacterium, has a mode of propelling itself forward in a directional fashion. However, there's been an intense debate whether this gliding process is mediated to the extracellular matrix by focal adhesion complexes or by viscous coupling. By combining our optical tweezers experiments about the motor activity under load with great computer modelling, we could essentially show that the predictions of a focal adhesion model hold! Even for high workloads, the motor complexes were not dragged over the extracellular matrix, but stayed in place. Taking into account the additional coupling between adhesion complexes essentially rules out that viscous coupling is the only source of extracellular adhesion.

The preprint of our paper has been on the arXiv for quite a while, but I'll keep you updated when PLOS Computational Biology "prints" it. I'm very happy that another piece of the work Mingzhai and I put into the understanding of the dynamics of Myxo motility lead to such a cool publication.


Talk at DPG International Spring Meeting

This is one of the best meetings on biophysics: The division Biological Physics at the German Physical Society Meeting, section Condensed Matter. It is extremely inspiring and stimulating, and, of course, a great chance to meet up with friends updating each other on the science we did during the past year. This year's meeting takes place in Dresden during the first week of April. In the course of a week, there are three (sometimes two) parallel sessions of presentations on biophysics followed by poster sessions, plus the chance to join the sessions of other sections (e.g. Chemical and Polymer Physics Division).

I'm very excited to present our recent results on the bacterium M. xanthus. Its gliding motors play an important role in the sporulation process, and we could grasp that function in a convincing series of optical tweezers and fluorescence experiments.

Directional Motors Move on Cell Surface and Give Rise to Gliding Motility and Sporulation in M. xanthus
Tue, Apr 1 2014, 14:00-14:15, HUEL 386, Session: BP 20

Eukaryotic cells utilize an arsenal of processive transport systems to deliver macromolecules to specific subcellular sites. In prokaryotes, such transport mechanisms have only been shown to mediate gliding motility, a form of microbial surface translocation. Here, we show that the motility function of the Myxococcus xanthus Agl-Glt machinery results from the specialization of a versatile class of bacterial transporters.

Specifically, we used fluorescence microscopy and optical traps to demonstrate that the Agl motility motor is modular and dissociates from the rest of the gliding machinery (the Glt complex) to bind the newly expressed Nfs complex, a close Glt paralogue, during sporulation. Following this association, the Agl system transports Nfs proteins directionally around the spore surface. Since the main spore coat polymer is secreted at discrete sites around the spore surface, its transport by Agl-Nfs ensures its distribution around the spore. Thus, the Agl-Glt/Nfs machineries may constitute a novel class of directional bacterial surface transporters that can be diversified to specific tasks depending on the cognate cargo and machinery-specific accessories.

I decided to give the fascinating story of sporulation and the important role of the motors as we unrevealed it by optical tweezers experiments a big chunk of the talk, and give those of you more interested in the genetics an opportunity to meet me following the session for an extended discussion. Hope to see you there, looking very much forward to your input.


New paper on myxo spore formation

M. xanthus (myxo) is a soil-dwelling, non-harmful bacteria, that became my personal case study into the fascinating world of bacteria motility. Myxo uses two different ways to propel itself forward, twitching and gliding; very much unlike E. coli that typically swims. In our studies, we learnt that the gliding motors also play an important role when myxo forms spores: the motors get recycled and move the spore coat forming machinery around "fresh" spores.

Left: One microbead is moved around a myxo spore whilst another microbead stays fixed.
Right: Fluorescently-tagged proteins move around a myxo spore.

Our collaborative paper with Tam Mignot's group just got published in PLoS Biology. I'm particularly thrilled about the feedback we've received already: The paper was highlighted by Mary Hoff and reviewed by Christina Kåhrström.

Of course, we've been telling the community about the work already: Tam presented it at a conference at the EMBL in Heidelberg in October 2013. In March, I'm presenting the whole story at the Meeting of the German Physical Society (DPG Tagung) in Dresden, and looking forward to discuss the impact of our findings in person.

So long, enjoy the read!

Morgane Wartel, Adrien Ducret, Shashi Thutupalli, Fabian Czerwinski, Anne-Valérie Le Gall, Emilia M. F. Mauriello, Ptissam Bergham, Yves V. Brun, Joshua W. Shaevitz and Tam Mignot, "A versatile class of cell surface directional motors gives rise to gliding motility and sporulation in Myxococcus xanthus," PLOS Biology 11(12) e1001728 (2013)
doi 10.1371/journal.pbio.1001728

Mary Hoff, "Agl, The Multitasking Motor Protein," PLOS Biology 11(12), e1001729 (2013)
doi 10.1371/journal.pbio.1001729

Christina T. Kåhrström, "Multitasking in Myxococcus," Nature Reviews Microbiology, published online 02 Jan 2014
doi 10.1038/nrmicro3202


Myxo at Imagine Science Film Festival

If you are a scientist, it is easy to get frustrated about how science is portrayed in movies. Or, how little the actual enjoyment of research observations gets used in filmmaking. At the Imagine Science Film Festival, the film category Scenes stands out in providing a collection of laboratory footage ready to be cut, edited, ... I thought it sounded like a great idea and submitted an overnight growing and swarming M. xanthus colony.Filmmakers combined it with other submissions to a nice piece that "world premiered" last Wednesday at the Bell House in Brooklyn, NY ;-)

Just like last year, I was participating in a lot of the festival sessions discussing film making of lab protocols, high precision camera techniques, and simply nurturing half-baked ideas about fun perspectives that melt one's perception of micro, meso and macro. One of those discussions lead to some semi-serious planning to shot a science short with Chloe Zimmermann. The festival in general was well organized and sponsored big, and there were good occasions to share opinions and knowledge, a perfect way to spend your time outside the lab.


Princeton’s Laboratory Learning Program

Cycling through Jersey after a remarkable experience this evening, I reflected a little about the just seen: At the Peddie School I had attended a dinner and a science fair in which the high school students had presented excellent laboratory work they'd had conducted over Summer. In posters and short talks I learnt about the diversity of plant species in Iceland and North Carolina, about the analysis of astronomical data, and inducible fluorescences in eukaryotic cell lines. Swetha Sanagavarapu had invited me since we had been working together on the extraction of bacterial species from soil samples. There is a little bit of a framework for highschool-university interactions at Princeton highlighted in the Laboratory Learning Program. For example, Swetha had prepared herself in a rigorous one-year course in biolaboratory techniques that allowed her to master some of our labs experiments with ease. Once arriving on campus, she had received the necessary safety training and had jumped right into the project.

For all the projects that the young students had explained to me tonight, I was impressed how knowledgable they had become on their topics, how determined they were to finish projects in such a timely manner of just six to eight weeks in an often totally new environment. The efforts Peddie School had put on together with Princeton and other universities is a great example that science education must be understood as a continuous process facilitated by all educational institutions at all levels of learning. Reminiscing along these lines, science fairs, Jugend forscht and other chances for young scientists to exchange and grow with their engagement are important. I kept on cycling ...


Biophysical Society Network Meeting PA 2012

My colleague Ben Bratton and I just returned from an exciting day at Lehigh University about 50mi East of Princeton. This year's Biophysical Society Network Meeting for Pennsylvania was an awesome opportunity to get in as much interesting science as fits in a single day. The list of speakers was pretty strong to begin with ranging from the innovative NMR research by Sharon Rozovsky to Phil Nelson, one of biophysics all-time heroes. In between, lucky me got a shot with a platform talk about our work on the gliding motors of M. xanthus, and I was thrilled about the positive feedback in the following discussions.

A good meeting always incorporates an outstanding poster session. In particular, I learnt a bunch from Moumita Das about the importance of crosslinkers in stabilizing the cytoskeleton.

Again, a great meeting with throughout awesome science, we need more of those regional network meetings.