Modestobacter multiseptatus gen. nov., sp nov., a budding actinomycete from soils of the Asgard Range (Transantarctic Mountains)

Oligotrophic PYGV medium, inoculated with soils from Linnaeus Terrace (1600 m, Antarctica), yielded four aerobic actinomycetes with short rods, multip le and irregular septa and often motile buds. Cells were 1.0-2.8 x 1.0-3.0 pm and colonies were beige to pink. The isolates were nearly identical in p hysiological and biochemical tests. Three strains grew from 0 degrees C to 25-28 degrees C, but one was psychrophilic with a maximum growth temperatur e of 20 degrees C. Carbon sources utilized were a-glucose, a-galactose, lac tose, sucrose or mannitol; malate, succinate, fumarate, pyruvate or glutara te were decarboxylated aerobically. Peptone and yeast extract were the pref erred nitrogen sources. Nitrate was reduced aerobically or anaerobically. C ell walls contained mesodiaminopimelic acid, glutamate, alanine, glycine, g alactose, glucose and ribose. Major fatty acids of strains AA-802, -824 -82 5 and -826(T) were n18:1, i16:0 and ai17:0. Major respiratory quinones were MK-S(H-4) and MK-8(H-4). Polar lipids were diphosphatidylglycerol, phospha tidylethanolamine and phosphatidylinositol. Phosphatidylglycerol was found in most strains. The DNA G+C contents were 68-70 mol%. In 16S rDNA analyses , similarity values obtained for 500 nucleotides from the 5' terminus were > 99.5 %. Almost complete sequences from AA-826(T) and 825 were 99.9 % simi lar. Strain AA-826T belonged to a novel cluster of desert soil and rock iso lates within the Geodermatophilaceae and was equidistantly related to membe rs of Geodermatophilus and to a Blastococcus lineage. The four isolates rep resent a new genus, Modestobacter gen. nov., with Modestobacter multiseptat us sp. nov. as the type species. The type strain, Modestobacter multiseptat us AA-826T, was deposited in the DSMZ as DSM 44406(T).