Three Chlamydomonas strains were isolated from the soils of a hot spring located in the Campi FlegreiCaldera (Naples, Italy). Ecophysiological, morpho-cytological and molecular features were used tocharacterize these isolates and to compare them with chlamydomonax acidophila strains from algalculture collections. The strains were collected from three points of the volcanic site, differing in theirphysico-chemical conditions. Among the examined Chlamydomonas strains, only the isolates from CampiFlegrei could grow optimally at pH valuesr3.0. These isolates also showed a high tolerance to desiccationand high temperatures, not evidenced by the other Chlamydomonas strains included in the study. 18SrDNA phylogeny indicates that the isolates from Campi Flegrei are closely related to Chlamydomonaspitschmannii and two strains isolated in Canada and Europe, that have been designated asChlamydomonas acidophila. A Chlamydomonas acidophila strain isolated from the type locality in Japanis less closely related according to its molecular phylogeny, and can also be discerned by light and electronmicroscopy.Moreover, vegetative cells and sporangia of Chlamydomonas acidophila from Japan showed amedian trilaminar structure not observed in the other strains. Our results show that Chlamydomonaspitschmannii could represent a hitherto unknown extremophilic Chlamydomonas species.
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