Hunting for cultivable Micromonospora strains in soils of the Atacama Desert

Innovative procedures were used to selectively isolate small numbers of Micromonospora strains from extreme hyper-arid and high altitude Atacama Desert soils. Micromonosporae were recognised on isolation plates by their ability to produce filamentous microcolonies that were strongly attached to the agar. Most of the isolates formed characteristic orange colonies that lacked aerial hyphae and turned black on spore formation, whereas those from the high altitude soil were dry, blue-green and covered by white aerial hyphae. The isolates were assigned to seven multi- and eleven single-membered groups based on BOX-PCR profiles. Representatives of the groups were assigned to either multi-membered clades that also contained marker strains or formed distinct phyletic lines in the Micromonospora 16S rRNA gene tree; many of the isolates were considered to be putatively novel species of Micromonospora. Most of the isolates from the high altitude soils showed activity against wild type strains of Bacillus subtilis and Pseudomonas fluorescens while those from the rhizosphere of Parastrephia quadrangulares and from the Lomas Bayas hyper-arid soil showed resistance to UV radiation

Micromonospora acroterricola sp. nov., a novel actinobacterium isolated from a high altitude Atacama Desert soil

A Micromonospora strain, designated 5R2A7T, isolated from a high altitude Atacama Desert soil was examined by using a polyphasic approach. Strain 5R2A7T was found to have morphological, chemotaxonomic and cultural characteristics typical of members of the genus Micromonospora . The cell wall contains meso- and hydroxy-diaminopimelic acid, the major whole-cell sugars are glucose, ribose and xylose, the predominant menaquinones MK-10(H4), MK-10(H6), MK-10(H8) and MK-9(H6), the major polar lipids diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and an unknown glycolipid, and the predominant cellular fatty acids iso-C16 : 0, iso-C15 : 0 and 10-methyl C17 : 0. The digital genomic DNA G+C content is 72.3 mol%. Phylogenetic analysis of the 16S rRNA gene sequence indicated that strain 5R2A7T was closely related to Micromonospora coriariae DSM 44875T (99.8 %) and Micromonospora cremea CR30T (99.7 %), and was separated readily from the latter, its closest phylogenetic neighbour, based on gyrB and multilocus sequence data, by low average nucleotide identity (92.59 %) and in silico DNA–DNA relatedness (51.7 %) values calculated from draft genome assemblies and by a range of chemotaxonomic and phenotypic properties. Consequently, strain 5R2A7T is considered to represent a novel species of Micromonospora for which the name Micromonospora acroterricola sp. nov. is proposed. The type strain is 5R2A7T (=LMG 30755T=CECT 9656T)