Introduction to Archaea Cell Biology

A collection of vocabulary flashcards covering the discovery, structure, metabolism, and biotechnology applications of the Domain Archaea.

Archaea

A domain of single-celled microorganisms representing a distinct branch on the tree of life, often thriving in extreme environments and possessing unique cellular characteristics.

Ether-linked lipids

A unique characteristic of archaeal membranes where branched isoprene chains are attached to glycerol via ether bonds ($C-O-C$), providing stability in extreme temperatures and pH.

S-layer

A crystalline protein or glycoprotein layer forming the outermost cell envelope in many archaea, offering structural rigidity, protection from osmotic lysis, and acting as a selective barrier.

Methanogenesis

A metabolic process unique to certain archaea that produces methane ($CH_4$) as a byproduct, typically by reducing carbon dioxide ($CO_2$) with hydrogen ($H_2$).

Chaperones

Proteins that assist in the proper folding and refolding of other proteins, preventing denaturation under high temperatures or other environmental stresses.

Compatible solutes

Small organic molecules accumulated by archaea to balance osmotic pressure and protect cellular components from environmental stress.

16S rRNA sequencing

A molecular method pioneered by Carl Woese to map evolutionary relationships, which led to the discovery of Archaea as a domain distinct from Bacteria and Eukarya.

Euryarchaeota

A diverse phylum of Archaea that includes methanogens, halophiles, and many thermophiles.

Asgard Archaea

A superphylum of Archaea believed to be the closest relatives to eukaryotes, potentially holding clues to the origin of eukaryotic cells.

DPANN Superphylum

A group of archaea often characterized by small cell sizes, reduced genomes, and a tendency to live as obligate symbionts with other archaea.

Hami

Complex, grappling hook-like external appendages found primarily in the Crenarchaeota phylum that facilitate strong surface attachment and biofilm formation.

Archaella

Specialized archaeal motility structures composed of multiple archaellin proteins, powered by $ATP$ hydrolysis, and growing from the base rather than the tip.

Pseudomurein

A cell wall polymer found in some archaea that structurally resembles bacterial peptidoglycan but contains N-acetyltalosaminuronic acid ($NAT$) and $\beta-1,3$ glycosidic bonds, making it resistant to lysozyme.

Bacteriorhodopsin (BR)

A light-driven proton pump in the cell membrane of haloarchaea that extrudes $H^+$ ions to create a proton motive force for $ATP$ synthesis.

Halorhodopsin (HL)

A light-driven chloride pump used by haloarchaea to import $Cl^-$ ions, helping to maintain osmotic balance and membrane potential.

Sensory rhodopsins

Light-sensitive proteins that act as photoreceptors, signaling to the archaellum to guide the cell's movement in response to light quality and intensity (phototaxis).

Reverse gyrase

A unique enzyme found in hyperthermophilic archaea that introduces positive supercoils into chromosomal $DNA$ to protect it from denaturation at high temperatures.

Histone homologs

Proteins in archaea structurally similar to eukaryotic histones that wrap and compact $DNA$ into tetramer-based superhelix structures.

TATA box

A promoter element in archaeal gene regulation that serves as a binding site for transcription factors, similar to those found in eukaryotes.

BRE (B recognition element)

A $DNA$ sequence found upstream of the TATA box in archaeal promoters, recognized by archaeal transcription factor B ($TFB$).

Extremozymes

Highly stable enzymes produced by archaea that remain active under extreme industrial conditions, such as high temperatures ($95^\text{o}C$) or corrosive pH levels.

Archaeosomes

Vesicles formed from archaeal membrane lipids that offer enhanced stability and are explored for use in drug delivery and vaccine administration.

Polyhydroxyalkanoates (PHAs)

Biodegradable bioplastics produced by some haloarchaea, such as Haloferax mediterranei, which serve as an environmentally friendly alternative to synthetic plastics.