Improved growth and morphological plasticity of Haloferax volcanii
- Publisher:
- Cold Spring Harbor Laboratory
- Publication Type:
- Journal Article
- Citation:
- BioRxiv, 2020
- Issue Date:
- 2020
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| Filename | Description | Size | |||
|---|---|---|---|---|---|
| 2020.05.04.078048v2.full.pdf | Accepted version | 1.76 MB |
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Abstract Some microbes display pleomorphism, showing variable cell shapes in a single culture, whereas others differentiate to adapt to changed environmental conditions. The pleomorphic archaeon Haloferax volcanii commonly forms discoid-shaped (‘plate’) cells in culture, but may also be present as rods, and can develop into motile rods in soft agar, or longer filaments in certain biofilms. Here we report improvement of H. volcanii growth in both semi-defined and complex media by supplementing with eight trace-element micronutrients. With these supplemented media, transient development of plate cells into uniformly-shaped rods was clearly observed during the early log phase of growth; cells then reverted to plates for the late log and stationary phases. In media prepared with high-purity reagents, without supplemental trace elements, rods and other complex elongated morphologies (‘pleomorphic rods’) were observed at all growth stages of the culture; the highly-elongated cells sometimes displayed a substantial tubule at one or less frequently both poles, as well as unusual tapered and highly-curved forms. Polar tubules were observed forming by initial mid-cell narrowing or tubulation, causing a dumbbell-like shape, followed by cell division towards one end. Formation of the uniform early-log rods, as well as the pleomorphic rods and tubules were dependent on the function of the tubulin-like cytoskeletal protein, CetZ1. Our results have revealed the remarkable morphological plasticity of H. volcanii , and shown that its changes in cell shape occur in response to multiple signals. Importance Microbes can show morphological responses to changed environmental conditions, which are important for their survival in a wide variety of environments. These conditions and the specific role of such morphological changes are poorly defined. Here we describe improved growth media for the model archaeon Haloferax volcanii , and the identification and characterization of environmental conditions— micronutrient starvation and culture dilution—that induce striking morphological responses. We show that the morphological changes require the tubulin-like cytoskeletal protein, CetZ1. We expect the discovery of these responses and the application of these conditions to facilitate the use of this species in ongoing studies of archaeal cell biology.
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