Archaeal biodiversity in crystallizer ponds from a solar saltern: Culture versus PCR

The culturable haloarchaeal diversity in a crystallizer pond from a solar s altern has been analyzed and compared with the biodiversity directly retrie ved by analysis of rRNA genes amplified from the environment. Two different sets of culture conditions have been assayed: solid medium with yeast extr act as carbon source and liquid media with either yeast extract or a mixtur e of fishmeal, Spirulina sp., and Artemia salina. Seventeen colonies grown on plates with yeast extract incubated at 30 degreesC were analyzed by 16S rDNA partial sequencing. Sixteen were closely related to haloarchaea of the genus Halorubrum; 13 of them to Halorubrum coriense, a haloarchaeon isolat ed from a solar saltern pond in Australia, which had not been previously is olated from the pond analyzed in this study; and one to Haloarcula marismor tui. Liquid cultures were analyzed by ribosomal internal spacer analysis (R ISA) and partial sequencing of the 16SrRNA genes. A total of 18 sequences w ere analyzed, 15 corresponding to RISA bands obtained from cultures, and 3 from the environmental sample used as inoculum. Thirteen sequences obtained from cultures were related to several Halorubrum species, and 2 to Haloarc ula. One of the crones obtained directly from the environmental sample was distantly related to a Natranobacterium, whereas mio were related to SPhT, the phylo-type most frequently retrieved from this environment by culture i ndependent techniques. Our results show an extremely low diversity for the haloarchaea retrieved by cultivation even when modifications to the standar d technique are introduced.