Abstract
Several haloarchaea are reported to be pleomorphic, while others exhibit remarkable shapes, such as squares. Recently, Haloferax volcanii was found to alter its morphology during growth. Cells are motile rods in early exponential phase, and immotile plates in stationary phase. It is unknown if this growth phase dependent cell shape alteration is a specific feature of Hfx. volcanii, or conserved amongst haloarchaea. Here, we studied the cell shape and motility of two haloarchaea species Haloarcula hispanica and Haloarcula californiae. With a combination of light and electron microscopy, we observed that both strains undergo a growth phase dependent morphological development, albeit in a slightly different fashion as Hfx. volcanii. For both Haloarcula strains, the cell size is changing throughout growth. Cell shape seems to be related with motility, as highly motile cells on semi-solid agar plates are predominantly rod-shaped. We conclude that the growth phase dependent cell morphology alteration might be a common feature amongst haloarchaea, and that cell shape is generally linked with a motile life style. The conservation of this phenomenon underscores the importance of studies of the molecular mechanisms regulating cell shape in archaea.
Highlights
We addressed the question if this growth phase dependent cell shape change is a specific characteristic of Hfx. volcanii, or if it is more common for haloarchaea
Our results show that both strains undergo growth phase dependent cell shape alteration (Figure 1)
These findings demonstrates that a growth phase dependent cell-shape change might be common amongst haloarchaea
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Microbial cells display great morphological diversity with varying shapes and sizes. Several underlying mechanisms have been discovered determining shape in bacteria and archaea [1,2,3,4,5]. The shape is uniform in the whole population, while in others this can vary depending on several conditions. The ability of a prokaryotic cell to actively restructure their shape in response to environmental conditions is called morphological plasticity. Pleomorphism describes a phenomenon in which a cellular population adapts its morphology depending on environmental factors or on growth phase
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