MORPHOLOGICAL AND MOLECULAR CHARACTERIZATION OF FOUR NOSTOC SPECIES ISOLATED FROM DESERT SOILS

Kubecková, K. 1 , Johansen, J. R. 1 , Li X. 2 & Vincent, J. 11 Department of Biology, John Carroll University, University Heights, OH 44118 USA; 2 Botany Department, Miami University, Oxford OH 45056 USA Four strains of Nostoc were isolated and characterized with regards to morphology and life cycle. Three strains were isolated from microbiotic soil crusts in the Mojave Desert of Southern California, and one strain was isolated from the lichen Collema tenax from crusts in Canyonlands National Park. All four strains were found to be morphologically distinct, with differences in: macrocolony appearance, microcolony shape and size, density of trichomes within the microcolony, and hormogonia production. The most commonly reported species from desert soils is Nostoc commune Vaucher. However, our strains all differ from that taxon in the size and shape of akinetes and heterocysts. Collema tenax is reported to have Nostoc commune as its phycobiont, but our observations on the phycobiont indicate that it is very distinct from that species and other Nostoc we have observed in desert soils. We subsequently sequenced a partial sequence of the 16SrRNA gene and the associated internal transcribed spacer (ITS) between the 16SrRNA and 23SrRNA genes for all four strains. Evidence of three multiple rRNA operons each was recovered for two strains, based upon configuration and sequence differences in the ITS regions. ITS with the following configurations were observed: no tRNA genes, tRNA Ile and tRNA Ala genes, and the beginning portion of tRNA Ile immediately followed by the end portion of tRNA Ala . Although our strains appear distinct from the descriptions of species in Geitler (1932) and Starmach (1966), further molecular characterization of species in this genus is probably warranted before they are assigned to existing or new species.