Abstract
Haloarchaea are remarkable organisms known for their vast morphological diversity. The pleomorphic haloarchaeaon Haloferax volcanii undergoes a morphological transition between
two distinct cell types: a motile rod-like state and a sessile, biofilm-producing disk-like state.
In our investigation of these shape transitions, we first characterized two novel cytoskeletal
proteins found to act at the onset of shape transitions, the first found with such a behavior.
These two archaeal bactofilin homologs, halofilin A and halofilin B, were found to be critical
in regulating proper surface curvature of Hfx. volcanii cells during the disk-to-rod transi
tion. Additionally, we investigated potential mechanisms for initiating the shape transition
and found that cells likely exhibit a combination of both quorum- and mechano-sensitive
responses. Finally, We developed further tools to study the role the S-layer, a flexible glyco
protein lattice that acts as the sole cell envelope in Hfx. volcanii, plays in cell morphogenesis.
All combined, this thesis makes substantial progress towards creating a comprehensive model
relating cell envelope, cytoskeletal elements, and sensing mechanisms in Haloferax volcanii.