ammustissa

Ammustissa is a genus of extremophilic archaea inhabiting hydrothermal vent ecosystems on the Pacific Mid‑Ocean Ridge. First described in 2023 by Li et al., the genus contains two named species: Ammustissa ventorum and Ammustissa profundus. These microorganisms are obligate hyperthermophiles that thrive in temperatures ranging from 80 to 105 °C and acidic pH values of 4.2 to 5.8. Morphologically, Ammustissa cells are coccoid to short oval rods up to 1.5 μm in diameter, lacking flagella but possessing a robust S‑layer that protects against high pressure and extreme temperatures.

Genomic analyses reveal a 1.8‑million base pair circular chromosome, with a GC content of 50.6 %. Ammustissa genomes encode unique enzymes involved in sulfur reduction and hydrogen oxidation, enabling chemolithoautotrophic growth. The genus is phylogenetically placed within the order Thermoproteales of the phylum Crenarchaeota, forming a clade distinct from the well‑known Sulfolobus and Pyrobaculum genera.

Ecologically, Ammustissa contributes to the biogeochemical cycling of sulfur and carbon in vent communities, forming symbiotic relationships with vent fauna and influencing metal speciation. The discovery of this genus expands the diversity of known extremophiles and provides a valuable model for studying protein stability and organization under intense thermal and chemical stress. Researchers are exploring potential biotechnological applications, such as thermostable enzymes for industrial processes, due to the resilience of Ammustissa proteins in high‑temperature environments.