Abstract
The taxonomic status, biotechnological and ecological potential of several Micromonospora strains isolated from an extreme hyper arid Atacama Desert soil were determined. Initially, a polyphasic study was undertaken to clarify the taxonomic status of five micromonosporae, strains LB4, LB19, LB32T, LB39T and LB41, isolated from an extreme hyper-arid soil collected from one of the driest regions of the Atacama Desert. All of the isolates were found to have chemotaxonomic, cultural and morphological properties consistent with their classification in the genus Micromonospora. Isolates LB32T and LB39T were distinguished from their nearest phylogenetic neighbours and proposed as new species, namely as Micromonospora arida sp. nov. and Micromonospora inaquosa sp. nov., respectively. Eluted methanol extracts of all of the isolates showed activity against a panel of bacterial and fungal indicator strains, notably against multi-drug resistant Klebsiella pneumoniae ATCC 700603 while isolates LB4 and LB41 showed pronounced anti-tumour activity against HepG2 cells. Draft genomes generated for the isolates revealed a rich source of novel biosynthetic gene clusters, some of which were unique to individual strains thereby opening up the prospect of selecting especially gifted micromonosporae for natural product discovery. Key stress-related genes detected in the genomes of all of the isolates provided an insight into how micromonosporae adapt to the harsh environmental conditions that prevail in extreme hyper-arid Atacama Desert soils.
Highlights
New natural products, especially antibiotics, are needed to control the spread of multi-drug resistant (MDR) microbial pathogens, as exemplified by MDR-resistant Gram-negative bacteria that are associated with high mortality rates[1,2]
The cultural, chemotaxonomic and morphological properties of the isolates were consistent with their classification in the genus Micromonospora[16,28]
The draft genomes of isolates LB4, LB19, LB32T, LB39T and LB41 have been deposited in GenBank under accession numbers QGSX00000000, QDGB00000000, QGSY00000000, QGSZ00000000, QGTA00000000, respectively, and are publically available
Summary
Chemotaxonomic, morphological and genomic properties of the isolates. In general, the cultural, chemotaxonomic and morphological properties of the isolates were consistent with their classification in the genus Micromonospora[16,28]. M. saelicesensis strain Lupac 09T, unlike isolate LB32T, grew at pH 9.0 and 45 °C, showed much greater activity in the API-ZYM tests, was oxidase positive, oxidised glycyl-L-proline and D-sorbitol and grew in the presence of lithium chloride, sodium bromate and sodium formate These differential characters are underscored by several chemotaxonomic traits, notably differences in fatty acid and whole cell sugar patterns (Table 2). Isolate LB39T can be distinguished from the type strain of M. chokoriensis, its closest phylogenetic neighbour, using a combination of chemotaxonomic and other phenotypic features (Table 2) The former, unlike the latter, produces α-mannosidase, oxidises L-arginine, D-serine #2, butyric acid and bromo-succinic acid and grows in the presence of minocycline, sodium chloride (4%, w/v) and potassium tellurite. It is evident that isolate LB19 belongs to the recently recognised species, Isolate Isolate LB4 LB41
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