Extremophiles features original research articles, reviews, and method papers on the biology, molecular biology, structure, function, and applications of microbial life at the edges of survivability. Conditions covered include high or low temperature, pressure, acidity, alkalinity, salinity, or desiccation; or in the presence of organic solvents, heavy metals, normally toxic substances, or radiation.The coverage incorporates aspects of multiple disciplines, including molecular biology, biodiversity, genetics, genomics, metagenomics, proteomics, bioinformatics, survival strategies, macromolecular structure, biotechnology, fermentation technology, ultrastructure, biotransformation, metabolism, enzymology, biomembranes, bioenergetics, biophysics, physiology, cell biology, symbiosis, ecology, bioremediation, methodologies, evolution, phylogeny, taxonomy, astrobiology, and others.

極端微生物以生物學、分子生物學、結構、功能和生存邊緣微生物生命應用方面的原始研究文章、綜述和方法論文為特色。所述條件包括高溫或低溫、壓力、酸度、堿度、鹽度或干燥;或在有機溶劑、重金屬、通常有毒物質或輻射的存在下。涵蓋多個學科領域，包括分子生物學、生物多樣性、遺傳學、基因組學、宏基因組學、蛋白質組學、生物信息學、生存策略、大分子結構、生物技術、發酵技術、超微結構、生物轉化、代謝、酶學、生物膜、生物能學、生物物理學、生理學、細胞生物學、共生、生態學、生物修復、方法學、進化、系統發育、分類學、天體生物學等。