Discovery of a dynamically unstable actin homolog, Salactin, through advances in Haloarchaeal imaging

Abstract

Archaea are fascinating extremophilic microorganisms that hold great potential for discoveries in cellular biology. Despite progress made in understanding the archaeal domain through metagenomic, biochemical, and structural information, little is known about how archaeal cells organize their internal cellular components in space and time. Studies of several processes could advance our understanding of archaeal cellular biology, including but not limited to cell shape propagation, cytoskeletal element, DNA replication, and chromosome segregation. While progress in our understanding has been made, further advancements in archaeal cellular biology could be made with the development or adaptation of imaging techniques to the archaeal domain. This thesis describes the usefulness of imaging technologies in progressing our understanding of archaeal cell biology, based on the imaging experience in bacteria and eukaryotes. In addition, two microfluidic devices were adapted for imaging two halophilic archaea, Halobacterium salinarum and Haloferax volcanii, both of which are well-suited for lab work and imaging. Advances in imaging techniques were used to further our understanding of a haloarchaeal actin homolog, Salactin, in H. salinarum. Salactin was initially thought to be involved in shape like its bacterial counterpart but was unexpectedly shown to be a dynamically unstable filament, similar to microtubule dynamics, and is important in low phosphate conditions when DNA segregation becomes more essential. Taken altogether, this thesis has demonstrated the potential of live-cell imaging in advancing our understanding of the cellular organization of archaeal cells in space and time. With increased live-cell imaging studies in archaea, I expect an explosion of amazing discoveries in archaea in the future.