[1] The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) [2] and National Center for Biotechnology Information (NCBI)[1] Fervidicoccaceae "Ignicoccaceae" Desulfurococcaceae 2 "Ignisphaeraceae" Pyrodictiaceae Desulfurococcaceae Caldisphaeraceae Acidilobaceae Sulfolobaceae Desulfurococcaceae Fervidicoccaceae Pyrodictiaceae "Ignicoccaceae" Acidilobaceae "Ignisphaeraceae" Zestosphaera {NBVN01} Sulfolobaceae Exposure of Sulfolobus solfataricus to the DNA damaging agents UV-irradiation, bleomycin or mitomycin C induces cellular aggregation.

Ajon et al.[10] showed that UV-induced cellular aggregation mediates chromosomal marker exchange with high frequency.

[citation needed] In another related species, Sulfolobus acidocaldarius, UV-irradiation also increases the frequency of recombination due to genetic exchange.

[12] The ups (UV-induced pilus) operon of Sulfolobus species is highly induced by UV irradiation.

The pili encoded by this operon are employed in promoting cellular aggregation, which is necessary for subsequent DNA exchange between cells, resulting in homologous recombination.