Genetic and morphological characteristics of two ecotypes of Eustigmatos calaminaris sp nov (Eustigmatophyceae) inhabiting Zn- and Pb-loaded calamine mine spoils

Knowledge on species diversity and distribution of eustigmatophycean algae (Stramenopiles) in the environment is currently very limited. Some of them are considered promising organisms for industrial application. Phylogenetic analysis of two strains (E120, E5) of a coccoid microalga isolated from highly Zn- and Pb-polluted calamine mine spoils revealed that they belong to the genus Eustigmatos. Cells of both strains were morphologically identical. Some features of their vegetative cells and zoospores differed from other described nominal Eustigmatos species. 18S rDNA sequences of E120 and E5 were identical but also differed in two or three nucleotide substitutions from the other Eustigmatos species (E. vischeri, E. magnus, E. polyphem). Only 1 - 3 nucleotide substitutions in 18S rDNA sequence were found among all the examined Eustigmatos species. ITS1-5.8S rDNA-ITS2 region was more variable (15 - 22 differences) than 18S rDNA, except for E120 and E5 strains which differed in only one nucleotide substitution (in 5.8S rDNA). Genetic differences found between the isolated strains (E120, E5) and the other Eustigmatos species were comparable to those observed among all nominal Eustigmatos species studied. This suggests that the isolates represent a new species. The name Eustigmatos calaminaris sp. nov. (referred to the locality) has been proposed. The E120 strain from the mine spoil with higher heavy metal contents was more Zn- and Pb-resistant than E5 from the less polluted ground. Their high, though varied resistance to Zn/Pb stress, together with the very slight genetic divergence between them, indicate that they represent two ecotypes of the same new species.