MinD2 modulates cell shape and motility in the archaeon .

In bacteria and archaea, proteins of the ParA/MinD family of ATPases regulate the spatiotemporal organization of various cellular cargoes, including cell division proteins, motility structures, chemotaxis systems, and chromosomes. In bacteria, such as , MinD proteins are crucial for the correct placement of the Z-ring at mid-cell during cell division. However, previous studies have shown that none of the 4 MinD homologs present in the archaeon have a role in cell division, suggesting that these proteins regulate different cellular processes in haloarchaea.

Archaeal type six secretion system mediates contact-dependent antagonism.

Microbial communities are shaped by cell-cell interactions. Although archaea are often found in associations with other microorganisms, the mechanisms structuring these communities are poorly understood. Here, we report on the structure and function of haloarchaeal contractile injection systems (CISs).

Role of VapBC4 toxin-antitoxin system of in heat stress adaptation.

Unlabelled: Toxin-antitoxin (TA) systems are important for stress adaptation in prokaryotes, including persistence, antibiotic resistance, pathogenicity, and biofilm formation. Toxins can cause cell death, reversible growth stasis, and direct inhibition of crucial cellular processes through various mechanisms, while antitoxins neutralize the effects of toxins. In bacteria, these systems have been studied in detail, whereas their function in archaea remains elusive.

The use of thermostable fluorescent proteins for live imaging in .

Introduction: Among hyperthermophilic organisms, protein localization is challenging due to the high growth temperatures that can disrupt proper folding and function of mostly mesophilic-derived fluorescent proteins. While protein localization in the thermophilic model archaeon has been achieved using antibodies with fluorescent probes in fixed cells, the use of thermostable fluorescent proteins for live imaging in thermophilic archaea has so far been unsuccessful. Given the significance of live protein localization in the field of archaeal cell biology, we aimed to identify fluorescent proteins for use in .

MinD2 modulates cell shape and motility in the archaeon .

In bacteria and archaea, proteins of the ParA/MinD family of ATPases regulate the spatiotemporal organization of various cellular cargoes, including cell division proteins, motility structures, chemotaxis systems, and chromosomes. In bacteria, such as , MinD proteins are crucial for the correct placement of the Z-ring at mid-cell during cell division. However, previous studies have shown that none of the 4 MinD homologs present in the archaeon have a role in cell division, suggesting that these proteins regulate different cellular processes in haloarchaea.

CryoEM reveals the structure of an archaeal pilus involved in twitching motility.

Amongst the major types of archaeal filaments, several have been shown to closely resemble bacterial homologues of the Type IV pili (T4P). Within Sulfolobales, member species encode for three types of T4P, namely the archaellum, the UV-inducible pilus system (Ups) and the archaeal adhesive pilus (Aap). Whereas the archaellum functions primarily in swimming motility, and the Ups in UV-induced cell aggregation and DNA-exchange, the Aap plays an important role in adhesion and twitching motility.

Adhesion pilus retraction powers twitching motility in the thermoacidophilic crenarchaeon Sulfolobus acidocaldarius.

Type IV pili are filamentous appendages found in most bacteria and archaea, where they can support functions such as surface adhesion, DNA uptake, aggregation, and motility. In most bacteria, PilT-family ATPases disassemble adhesion pili, causing them to rapidly retract and produce twitching motility, important for surface colonization. As archaea do not possess PilT homologs, it was thought that archaeal pili cannot retract and that archaea do not exhibit twitching motility.

Distinct life cycle stages of an ectosymbiotic DPANN archaeon.

DPANN archaea are a diverse group of microorganisms that are thought to rely on an ectosymbiotic lifestyle; however, the cell biology of these cell-cell interactions remains largely unknown. We applied live-cell imaging and cryo-electron tomography to the DPANN archaeon Nanobdella aerobiophila and its host, revealing two distinct life cycle stages. Free cells possess archaella and are motile.

Proteins containing photosynthetic reaction centre domains modulate FtsZ-based archaeal cell division.

Cell division in all domains of life requires the orchestration of many proteins, but in Archaea most of the machinery remains poorly characterized. Here we investigate the FtsZ-based cell division mechanism in Haloferax volcanii and find proteins containing photosynthetic reaction centre (PRC) barrel domains that play an essential role in archaeal cell division. We rename these proteins cell division protein B 1 (CdpB1) and CdpB2.

Archaeal GPN-loop GTPases involve a lock-switch-rock mechanism for GTP hydrolysis.

GPN-loop GTPases have been found to be crucial for eukaryotic RNA polymerase II assembly and nuclear trafficking. Despite their ubiquitous occurrence in eukaryotes and archaea, the mechanism by which these GTPases mediate their function is unknown. Our study on an archaeal representative from showed that these dimeric GTPases undergo large-scale conformational changes upon GTP hydrolysis, which can be summarized as a lock-switch-rock mechanism.

Application of the endogenous CRISPR-Cas type I-D system for genetic engineering in the thermoacidophilic archaeon .

CRISPR (clustered regularly interspaced short palindromic repeats)-Cas systems are widely distributed among bacteria and archaea. In this study, we demonstrate the successful utilization of the type I-D CRISPR-Cas system for genetic engineering in the thermoacidophilic archaeon . Given its extreme growth conditions characterized by a temperature of 75°C and pH 3, an uracil auxotrophic selection system was previously established, providing a basis for our investigations.

"Influence of plasmids, selection markers and auxotrophic mutations on cell shape plasticity".

and other Haloarchaea can be pleomorphic, adopting different shapes, which vary with growth stages. Several studies have shown that cell shape is sensitive to various external factors including growth media and physical environment. In addition, several studies have noticed that the presence of a recombinant plasmid in the cells is also a factor impacting cell shape, notably by favoring the development of rods in early stages of growth.

adhesion pili power twitching motility in the absence of a dedicated retraction ATPase.

Type IV pili are ancient and widespread filamentous organelles found in most bacterial and archaeal phyla where they support a wide range of functions, including substrate adhesion, DNA uptake, self aggregation, and cell motility. In most bacteria, PilT-family ATPases disassemble adhesion pili, causing them to rapidly retract and produce twitching motility, important for surface colonization. As archaea do not possess homologs of PilT, it was thought that archaeal pili cannot retract.

Archaeal type IV pili stabilize Haloferax volcanii biofilms in flow.

Multicellular communities of contiguous cells attached to solid surfaces called biofilms represent a common microbial strategy to improve resilience in adverse environments. While bacterial biofilms have been under intense investigation, whether archaeal biofilms follow similar assembly rules remains unknown.Haloferax volcanii is an extremely halophilic euryarchaeon that commonly colonizes salt crust surfaces.

Putative nucleotide-based second messengers in archaea.

Second messengers transfer signals from changing intra- and extracellular conditions to a cellular response. Over the last few decades, several nucleotide-based second messengers have been identified and characterized in especially bacteria and eukaryotes. Also in archaea, several nucleotide-based second messengers have been identified.

Stay or Go: Sulfolobales Biofilm Dispersal Is Dependent on a Bifunctional VapB Antitoxin.

A type II VapB14 antitoxin regulates biofilm dispersal in the archaeal thermoacidophile Sulfolobus acidocaldarius through traditional toxin neutralization but also through noncanonical transcriptional regulation. Type II VapC toxins are ribonucleases that are neutralized by their proteinaceous cognate type II VapB antitoxin. VapB antitoxins have a flexible tail at their C terminus that covers the toxin's active site, neutralizing its activity.

Systematic comparison of unilamellar vesicles reveals that archaeal core lipid membranes are more permeable than bacterial membranes.

One of the deepest branches in the tree of life separates the Archaea from the Bacteria. These prokaryotic groups have distinct cellular systems including fundamentally different phospholipid membrane bilayers. This dichotomy has been termed the lipid divide and possibly bestows different biophysical and biochemical characteristics on each cell type.

Archaella Isolation.

Swimming archaea are propelled by a filamentous structure called the archaellum. The first step for the structural characterization of this filament is its isolation. Here we provide various methods that allow for the isolation of archaella filaments from well-studied archaeal model organisms.

Electron cryo-microscopy reveals the structure of the archaeal thread filament.

Pili are filamentous surface extensions that play roles in bacterial and archaeal cellular processes such as adhesion, biofilm formation, motility, cell-cell communication, DNA uptake and horizontal gene transfer. The model archaeaon Sulfolobus acidocaldarius assembles three filaments of the type-IV pilus superfamily (archaella, archaeal adhesion pili and UV-inducible pili), as well as a so-far uncharacterised fourth filament, named "thread". Here, we report on the cryo-EM structure of the archaeal thread.

The cell biology of archaea.

The past decade has revealed the diversity and ubiquity of archaea in nature, with a growing number of studies highlighting their importance in ecology, biotechnology and even human health. Myriad lineages have been discovered, which expanded the phylogenetic breadth of archaea and revealed their central role in the evolutionary origins of eukaryotes. These discoveries, coupled with advances that enable the culturing and live imaging of archaeal cells under extreme environments, have underpinned a better understanding of their biology.

Methods to Analyze Motility in Eury- and Crenarchaea.

Many archaea display swimming motility in liquid medium, which is empowered by the archaellum. Directional movement requires a functional archaellum and a sensing system, such as the chemotaxis system that is used by Euryarchaea. Two well-studied models are the euryarchaeon Haloferax volcanii and the crenarchaeon Sulfolobus acidocaldarius.

Progress and Challenges in Archaeal Cell Biology.

Over the past decades there has been a growing interest in the domain of archaea. In this chapter we highlight the recent advances that have been made in studying the cell biology of archaea. We particularly focus on methods for genetic manipulation and imaging of different archaeal species and discuss the technical limitations at the often-extreme growth conditions.

Methods for Markerless Gene Deletion and Plasmid-Based Expression in Sulfolobus acidocaldarius.

A well-functioning genetic system, which is important for studying gene functions in vivo, requires a transformation method, a vector system and a selection system. Sulfolobus acidocaldarius is a crenarchaeal model organism that grows optimally at 75 °C and a pH of 3. These extreme growth conditions cause some difficulties in developing a genetic system.

Structural insights into the mechanism of archaellar rotational switching.

Signal transduction via phosphorylated CheY towards the flagellum and the archaellum involves a conserved mechanism of CheY phosphorylation and subsequent conformational changes within CheY. This mechanism is conserved among bacteria and archaea, despite substantial differences in the composition and architecture of archaellum and flagellum, respectively. Phosphorylated CheY has higher affinity towards the bacterial C-ring and its binding leads to conformational changes in the flagellar motor and subsequent rotational switching of the flagellum.

Towards Elucidating the Rotary Mechanism of the Archaellum Machinery.

Motile archaea swim by means of a molecular machine called the archaellum. This structure consists of a filament attached to a membrane-embedded motor. The archaellum is found exclusively in members of the archaeal domain, but the core of its motor shares homology with the motor of type IV pili (T4P).