Vogl, K. | bioRxiv Science

bioRxiv2026

Control of motility and cell shape of Haloferax volcanii is linked by a transcriptional regulator

Archaea rely on motility and morphological plasticity to navigate their environments, yet the transcriptional regulation of these processes remains poorly understood. In Haloferax volcanii, archaellum-dependent motility is transcriptionally regulated, but an EarA-like master regulator is absent. Here, we identify CsmR as a transcriptional regulator that links archaellum biogenesis and cell-shape transitions in H. volcanii. Deletion of csmR abolished detectable motility, whereas overexpression increased motility and promoted a sustained rod-like morphology. Comparative transcriptomics defined a CsmR-associated regulon that includes archaellum and chemotaxis genes as well as rod-shape determinants (e.g., Sph3 and RdfA), and upstream motif enrichment supports a direct role for CsmR in transcriptional control. Furthermore, csmR and cirA, a KaiC-like regulator, share extensive transcriptional overlap, with CirA likely fine-tuning CsmR-mediated regulation through post-translational modification. These findings establish CsmR as a key integrator of motility and cell shape regulation in Haloferax volcanii, suggesting that haloarchaea coordinate these fundamental processes through an unidentified transcriptional network. Moreover, Northern blotting and cell shape observation suggest that transcription factor RosR is involved in the regulation of an sRNA that shares extensive overlap with the cirA gene, possibly fine-tuning the effect of CirA on the regulation of the archaellum cluster and the rod shape determinants sph3 and rdfA. Understanding this interplay provides new insights into archaeal adaptability and may reveal broader regulatory principles in prokaryotic cell biology.

microbiology↗

bioRxiv2023

Uncovering the temporal dynamics and regulatory networks of thermal stress response in a hyperthermophile using transcriptomics and proteomics

Extremophiles, such as the hyperthermophilic archaeon Pyrococcus furiosus, thrive under extreme conditions and must rapidly adapt to changes in the physical parameters of their natural environment for short-term and long-term survival. When inhabiting hydrothermal vents, these organisms face substantial temperature gradients, necessitating the evolution of adaptive thermal stress mechanisms. However, the dynamics and coordination of cellular responses at the transcriptome and proteome levels remain underexplored. This study presents an integrated analysis of RNA-sequencing and mass spectrometry data to elucidate the transcriptomic and proteomic responses to heat and cold shock stress and recovery in P. furiosus. Our results reveal surprisingly rapid and dynamic changes in gene and protein expression patterns associated with these stress responses. Heat shock triggers extensive transcriptome reprogramming, orchestrated by the transcriptional regulator Phr, which targets a broader gene repertoire than previously demonstrated. For heat shock signature genes, RNA levels swiftly return to baseline upon recovery, while protein levels remain persistently upregulated, reflecting a rapid but more sustained response. Intriguingly, cold shock at 4{degrees}C elicits distinct short-term and long-term responses at both RNA and protein levels. By conducting a cluster analysis, we identified gene sets with either congruent or contrasting trends in RNA and protein changes. Notably, these clusters represent well-separated arCOG groups and appear to be tailored to their individual cellular responses. Our study provides a comprehensive overview of the cellular response to temperature stress, advancing our understanding of stress response mechanisms in hyperthermophilic archaea and provide valuable insights into the molecular adaptations that facilitate life in extreme environments.

microbiology↗