Modestobacter altitudinis sp. nov., a novel actinobacterium isolated from Atacama Desert soil.

Three presumptive Modestobacter strains isolated from a high altitude Atacama Desert soil were the subject of a polyphasic study. The isolates, strains 1G4T, 1G51 and 1G52, were found to have chemotaxonomic and morphological properties that were consistent with their assignment to the genus Modestobacter. They formed a well supported clade in Modestobacter 16S rRNA gene trees and were most closely related to the type strain of 'Modestobacter excelsi' (99.8-99.9% similarity). They were also closely related to the type strains of Modestobacter caceresii (99.6 % similarity), Modestobacter italicus (99.7-99.9% similarity), Modestobacter lacusdianchii (98.4-99.2% similarity), Modestobacter marinus (99.4-99.5% similarity) and Modestobacter roseus (99.3-99.5% similarity), but were distinguished from their closest relatives by a combination of phenotypic features. Average nucleotide identity and digital DNA:DNA hybridization similarities drawn from comparisons of draft genome sequences of isolate 1G4T and its closest phylogenetic neighbours mentioned above, were well below the threshold used to assign closely related strains to the same species. The close relationship between isolate 1G4T and the type strain of M. excelsi was showed in a phylogenomic tree containing representative strains of family Geodermatophilaceae. The draft genome sequence of isolate 1G4T (size 5.18 Kb) was shown to be rich in stress related genes providing further evidence that the abundance of Modestobacter propagules in Atacama Desert habitats reflects their adaptation to the harsh environmental conditions prevalent in this biome. In light of all of these data it is proposed that the isolates be assigned to a novel species in the genus Modestobacter. The name proposed for this taxon is Modestobacter altitudinis sp. nov., with isolate 1G4T (=DSM 107534T=PCM 3003T) as the type strain.

Blastococcus atacamensis sp. nov., a novel strain adapted to life in the Yungay core region of the Atacama Desert.

A polyphasic study was undertaken to establish the taxonomic status of a Blastococcus strain isolated from an extreme hyper-arid Atacama Desert soil. The isolate, strain P6T, was found to have chemotaxonomic and morphological properties consistent with its classification in the genus Blastococcus. It was shown to form a well-supported branch in the Blastococcus 16S rRNA gene tree together with the type strains of Blastococcus capsensis and Blastococcus saxobsidens and was distinguished from the latter, its close phylogenetic neighbour, by a broad range of phenotypic properties. The draft genome sequence of isolate P6T showed 84.6 % average nucleotide identity, 83.0 % average amino acid identity and a digital DNA-DNA hybridisation value of 27.8 % in comparison with the genome sequence of B. saxobsidens DSM 44509T, values consistent with its assignment to a separate species. Based on these data it is proposed that isolate P6T (NCIMB 15090T=NRRL B-65468T) be assigned to the genus Blastococcus as Blastococcus atacamensis sp. nov. Analysis of the whole genome sequence of B. atacamensis P6T, with 3778 open reading frames and a genome size of 3.9 Mb showed the presence of genes and gene clusters that encode for properties that reflect its adaptation to the extreme environmental conditions that prevail in Atacama Desert soils.

Geodermatophilus chilensis sp. nov., from soil of the Yungay core-region of the Atacama Desert, Chile.

A polyphasic study was undertaken to establish the taxonomic status of three representative Geodermatophilus strains isolated from an extreme hyper-arid Atacama Desert soil. The strains, isolates B12T, B20 and B25, were found to have chemotaxonomic and morphological properties characteristic of the genus Geodermatophilus. The isolates shared a broad range of chemotaxonomic, cultural and physiological features, formed a well-supported branch in the Geodermatophilus 16S rRNA gene tree in which they were most closely associated with the type strain of Geodermatophilus obscurus. They were distinguished from the latter by BOX-PCR fingerprint patterns and by chemotaxonomic and other phenotypic properties. Average nucleotide identity, average amino acid identity and digital DNA-DNA hybridization values between the whole genome sequences of isolate B12T and G. obscurus DSM 43160T were 89.28%, 87.27% and 37.4%, respectively, metrics consistent with its classification as a separate species. On the basis of these data, it is proposed that the isolates be assigned to the genus Geodermatophilus as Geodermatophilus chilensis sp. nov. with isolate B12T (CECT 9483T=NCIMB 15089T) as the type strain. Analysis of the whole genome sequence of G. chilensis B12T with 5341 open reading frames and a genome size of 5.5Mb highlighted genes and gene clusters that encode for properties relevant to its adaptation to extreme environmental conditions prevalent in extreme hyper-arid Atacama Desert soils.

Geodermatophilus brasiliensis sp. nov., isolated from Brazilian soil.

A Gram-reaction-positive bacterial isolate, designated Tü 6233(T), with rudimentary, coral-pink vegetative mycelium that formed neither aerial mycelium nor spores, was isolated from a Brazilian soil sample. Chemotaxonomic and molecular characteristics of the isolate matched those described for members of the genus Geodermatophilus. Cell-wall hydrolysates contained meso-diaminopimelic acid as the diagnostic diamino acid and galactose as the diagnostic sugar. The major fatty acids were iso-C(16 : 0), iso-C(15 : 0) and C(17 : 1)ω8c and the predominant menaquinone was MK-9(H4). The polar lipids consisted of diphosphatidylglycerol, phosphatidylethanolamine, hydroxyphosphatidylethanolamine, phosphatidylinositol, an unknown glycophospholipid and an unknown phospholipid. The DNA G+C content of the strain was 75.4 mol%. The 16S rRNA gene sequence identity with members of the genus Geodermatophilus was 94.2-98.7%. Based on phenotypic, chemotaxonomic and phylogenetic data, strain Tü 6233(T) is proposed to represent a novel species, Geodermatophilus brasiliensis sp. nov., with the type strain Tü 6233(T) ( = DSM 44526(T) = CECT 8402(T)).