Sulfolobus solfataricus and Sulfolobus acidocaldarius are hyperthermophilic archaea. Exposure of these organisms to the DNA damaging agents UV irradiation, bleomycin or mitomycin C induces species-specific cellular aggregation. UV-induced cellular aggregation of S. acidocaldarius mediates chromosomal marker exchange with high frequency. Recombination rates exceed those of uninduced cultures by up to three orders of magnitude. Frols et al. and Ajon et al. hypothesized that cellular aggregation enhances species-specific DNA transfer between Sulfolobus cells in order to repair damaged DNA by means of homologous recombination. Van Wolferen et al. noted that this DNA exchange process may be crucial under DNA damaging conditions such as high temperatures. It has also been suggested that DNA transfer in Sulfolobus may be an early form of sexual interaction similar to the more well-studied bacterial transformation systems that involve species-specific DNA transfer leading to homologous recombinational repair of DNA damage (and see Transformation (genetics)).
sulfolObUs SoLFataricus aNd sULfolObuS aciDocaLdariuS are hYpertHErmophilic arChaEa. eXpoSUre oF thEsE organIsMs to the dnA damagiNg agENts uV IRrADiATion, bleomYcin or mitomYciN C InDucEs speciEs-sPecIfiC Cellular AGGregAtIoN. Uv-indUceD cellulaR aggregaTioN of s. aCidoCALDArius meDiates ChRomosomal marker exchanGe with high freQueNcy. rECOMbiNatIon rates exceEd tHoSE Of uNINDUCed CultuRes By up To thrEe oRDErs oF mAgnItude. frolS et AL. and aJon et AL. HYPOtHEsized thAt CellULaR AGgregAtion eNhAnCEs specIes-SpecifiC dNA Transfer betwEen sULfolObus ceLls in ORder TO repAir damageD dna bY meAns oF HomoLogous rEcOmBinAtioN. vaN WolfeREn ET Al. noteD tHat tHiS Dna exchangE proCess may be cRUCIal uNdeR dna damaGiNG ConDitionS SUch aS HIgh TeMpeRatuRes. It hAS alSO bEEN SUGgEsted thaT dna traNsFeR in suLfOlobUS maY bE An eArly fOrm oF sexUal interaction simIlar to the MoRe WEll-sTudied bacTErial tranSFoRmATion sySteMs That InvoLvE sPECies-specific dna TranSfer LeaDinG tO hOMOLogOus ReCombinationaL Repair oF dna dAmAge (anD see transformAtIon (gENeticS)).