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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - CCDSA (Control of cell division in Sulfolobus acidocaldarius)

Teaser

Summary

Eukaryotes evolved from a symbiotic merger of an archaeal host with a bacterial endosymbiont, prompting a dramatic and extensive reorganisation of cellular structure. Despite having diverged approximately 2 billion years ago, extant archaea and eukaryotes share core aspects of cell cycle control and conserved components of the cell division machinery. Comparative genomic analyses predict that the archaeal cell cycle could serve as a streamlined, minimal model for the far more elaborate eukaryotic one- yet little is known about how most archaea grow and divide. In proposing to use a combination of high-resolution imaging, genetics and quantitative cell biology to investigate the cell cycle of the model archaeon Sulfolobus acidocaldarius, we had two primary goals: to establish an archaeal model for the cell cycle, and to gain new insights into eukaryotic cell cycle control through an understanding of its origins.

Work performed

We have created tools and established protocols for the imaging of fixed and inert, live Sulfolobus cells using super-resolution and conventional microscopy. These, along with optimised synchronization methods and FACS assays, have helped us construct a complete, high-resolution timeline of the Sulfolobus cell cycle. This temporal map has nucleated two new projects in the lab, focused on chromosome dynamics, and on ESCRTIII-mediated cell division - both with major implications for our understanding of the evolution of eukaryotic cell cycle control.

We have constructed the first ever live-imaging setup for a thermophilic organism using a custom-built microscope. We have used this to corroborate our data from fixed, staged cells using membrane and DNA dyes stable at high temperature. Building upon this base, we expect to monitor real-time cell cycle dynamics. We also expect that this platform will be easily adapted to the imaging of other extremophilic organisms, many of which are of commercial interest.

Our data on cell cycle dynamics will be used to inform an ongoing genetic screen for new cell cycle regulators. In the meantime, we have used phylogenetic analyses to link our collaboratorsâ€™ and our findings in Sulfolobus to the newly discovered uncultured Asgard archaea that appear to be the closest known relatives of eukaryotes. We have also identified structural analogies to eukaryotic nuclear remodelling, a process we are currently investigating using fission yeast as a model.

Much of this work has been carried out in close collaboration with the Henriques lab at UCL, the Lindas lab at Stockholm University, and the Ettema lab at Uppsala University. The work has helped the Baum lab and collaborators obtain further funding from the BBSRC and the Wellcome Trust, and we expect the bulk of these results to be published within the year or so.

Final results

We expect that this work will make Sulfolobus a better model for archaeal cell biology in general and archaeal cell cycle control in particular. To aid this, we will disseminate our novel tools and protocols as quickly, widely and openly as possible. In particular, we hope that the live imaging platform, to our knowledge the only one of its kind, will prove useful to a large community of researchers interested in the growth, division and ecology of this understudied domain of life.

We also expect that this work on archaea will have implications for our understanding of core cell cycle control in eukaryotes- including testable predictions that can be assessed using comparative experimental approaches in key eukaryotic model systems such as yeast or human cell lines.