Two Gram-positive, non-motile and aerobic bacteria were isolated from a water sample of the hypersaline Ekho Lake, Antarctica. The cocci or short rods grew well on oligotrophic PYGV agar of pH 7.5 and at 26 degrees C. Strains EL-17KT and EL-17AT both required thiamine and biotin, strain EL-17AT also required nicotinic acid. Carbon sources utilized by both strains were acetate, pyruvate, alpha-D-glucose, glutamate and (weakly) citrate, but succinate, malate or butyrate were utilized only by EL-17KT. Gelatin, starch and DNA were hydrolyzed, NH, was formed from peptone, and nitrate was reduced aerobically by both strains. The isolates had the same temperature tolerance for growth in the range tested (below 3 to above 33.5 degrees C) and pH range (<5.5 to >9.5) and were sensitive to chloramphenicol and penicillin G. Their cell walls contained LL-diaminopimelic acid and had a single glycine residue as interpeptide bridge. Strain EL-17AT contained glycine at position 1 of the peptide subunit (peptidoglycan type A 3gamma'). Isolates EL-17KT and EL-17AT differed in their maximum NaCl tolerance, which was 15% or 6-8%, respectively. The major fatty acid of EL-17KT was C18:1 and that of EL-17AT was ai-C15:0. The major respiratory quinones of EL-17KT and EL-17AT were MK-8(H4) and MK-9(H4), respectively. The former isolate had 69 mol% G+C, the latter had 73 mol% G+C. Comparative 16S rRNA gene sequencing revealed phylogenetic relationships of isolate EL-17KT with the genus Nocardioides, with N. pyridinolyticus and N. plantarum as the closest relatives. Phenotypic and genotypic characteristics support the description of a new species, Nocardioides aquaticus sp. nov., with EL-17KT as the type strain (= DSM 11439T). Isolate EL-17AT is related to the genus Friedmanniella, with E antarctica and E spumicola as the closest relatives. The differentiating characteristics support the description of a new species, Friedmanniella lacustris sp. nov., with EL-17AT as the type strain (= DSM 11465T).