Keywordsarchaea; ecology; oxidative stress; metals; natural habitats; survival strategies; molecular mechanisms; lysozyme; dUTPase; trehalose; structure; dynamics; spectroscopic techniques; gas vesicles; Halobacterium; Haloferax; Haloquadratum; Haloplanus; Halogeometricum; bacteriorhodopsin; oxygen; halophiles; extremophiles; hydrolases; saline environments; Caldicellulosiruptor saccharolyticus; biohydrogen; dark fermentation; cellulolytic thermophile; thermodynamics; rhamnose metabolism; pyrophosphate; redox balance; hydrogen inhibition; regulation; archaella; archaeal flagella; archaella; type IV pili; hami; cannulae; bindosome; glycosylation; archaeal virus; thermophile; structural homology; archaea; quorum sensing; extremophiles; microbial communication; ABC transporters; periplasmic binding proteins; arginine; structural stability; unfolding; antipredator behavior; hydrogen sulfide; Poecilia; predator avoidance; predator recognition; L-glutamate sources; glutamate racemase; PGA chirality; archaea; bacteria; Acidithiobacillus; acid mine drainage (AMD); acid streamers; Actinobacteria; Ferrovum; iron oxidation; microbial communities; hot spring; field campaign; interdisciplinary; extreme environment; osmoadaptation; chloride accumulation; compatible solutes; hybrid strategy; Halococcus species; Halococcus salifodinae; haloarchaea; Permian salt deposit; cell wall polymer; polyhydroxyalkanoate; prokaryotic evolution; hypersaline environments; halophiles; quorum sensing; N-acyl homoserine lactones; Halomonadaceae; Raman spectroscopy; extremophile; bio-strategy; geo-strategy; microorganism; magnetotactic bacteria; biomineralization; magnetite; greigite; biodiversity and ecology; extreme environments; extremophiles; astrobiology; metagenomics; hot springs; thermophiles; hypersaline; protist; eukaryote; microbialite; saltern; DHAB; Hamelin Pool; E. Mediterranean Sea; foraminifera; SSU rRNA; acidophiles; eukaryots; extremophiles; extreme environments; photosynthesis; Río Tinto; D-family DNA polymerase; DNA replication; binding domain; molecular structure; hyperthermophilic archaea; Pyrococcus; n/a; anaerobic thermophiles; thermal ecosystems; extremophiles; deep-sea; taxonomy; biotechnology