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Bacteria belonging to the phylum Actinobacteria are a very good source of antibiotics, and indeed dominate the current clinical antibiotic space. This paper reports Mutactimycin AP, a new compound belonging to an anthracycline-type family of antibiotics, isolated from a Saccharothrix sp. This actinobacterial strain was isolated from the rhizosphere of lupine plants growing in the extreme hyper-arid Atacama Desert. Structural characterization was carried out using electrospray ionization-mass spectrometry (ESI-MS) and NMR spectroscopy in combination with molecular modelling. The compound was tested against the ESKAPE pathogens, where it showed activity against MRSA and five strains associated with bovine mastitis, where it showed activity against Enterococcus pseudoavium and Staphylycoccus Aureus subsp. Aureus .

Three dermacozines, dermacozines N-P ( 1 - 3 ), were isolated from the piezotolerant Actinomycete strain Dermacoccus abyssi MT 1.1 T , which was isolated from a Mariana Trench sediment in 2006. Herein, we report the elucidation of their structures using a combination of 1D/2D NMR, LC-HRESI-MS n , UV-Visible, and IR spectroscopy. Further confirmation of the structures was achieved through the analysis of data from density functional theory (DFT)-UV-Visible spectral calculations and statistical analysis such as two tailed t -test, linear regression-, and multiple linear regression analysis applied to either solely experimental or to experimental and calculated 13 C-NMR chemical shift data. Dermacozine N ( 1 ) bears a novel linear pentacyclic phenoxazine framework that has never been reported as a natural product. Dermacozine O ( 2 ) is a constitutional isomer of the known dermacozine F while dermacozine P ( 3 ) is 8-benzoyl-6-carbamoylphenazine-1-carboxylic acid. Dermacozine N ( 1 ) is unique among phenoxazines due to its near infrared (NIR) absorption maxima, which would make this compound an excellent candidate for research in biosensing chemistry, photodynamic therapy (PDT), opto-electronic applications, and metabolic mapping at the cellular level. Furthermore, dermacozine N ( 1 ) possesses weak cytotoxic activity against melanoma (A2058) and hepatocellular carcinoma cells (HepG2) with IC 50 values of 51 and 38 μM, respectively.

Whole genome sequences of four bacterial strains Dietzia maris SST1, Pseudomonas zhaodongensis SST2, Pseudomonas sp. SST3 and Halomonas sulfidaeris SST4, recovered from the South Shetland Trench sediment in Antarctica were analyzed using Ion Torrent sequencing technology. The respective sizes of their genomes (3.88, 4.99, 5.60 and 4.25 Mb) and GC contents (70.0, 60.3, 59.9 and 53.8%) are in agreement with these values of other strains of the species. The bacterial strains displayed promising antimicrobial activity against a number of pathogenic bacterial and fungal species. Whole genomes have been assembled and biosynthetic gene clusters (BGCs) have been identified using the antibiotics and Secondary Metabolite Analysis Shell (antiSMASH) web platform. Comparative analysis of the genome sequences revealed that the strains host abundant BGCs encoding for terpenes, siderophores, arylpolyene, bacteriocins, and lassopeptides. Furthermore, the key stress-related genes were identified and their distribution provided an insight into how these isolates adapt to key marine environmental conditions. This comprehensive study is a contribution to understanding the nature of life on the deep-sea environments., (Copyright © 2020 Elsevier B.V. All rights reserved.)

In this paper, we report on the chemistry of the rare South African Actinomycete Kribbella speibonae strain SK5, a prolific producer of hydroxamate siderophores and their congeners. Two new analogues, dehydroxylated desferrioxamines, speibonoxamine 1 and desoxy-desferrioxamine D 1 2 , have been isolated, together with four known hydroxamates, desferrioxamine D 1 3 , desferrioxamine B 4 , desoxy-nocardamine 5 and nocardamine 6 , and a diketopiperazine (DKP) 7 . The structures of 1 - 7 were characterized by the analysis of HRESIMS and 1D and 2D NMR data, as well as by comparison with the relevant literature. Three new dehydroxy desferrioxamine derivatives 8 - 10 were tentatively identified in the molecular network of K. speibonae strain SK5 extracts, and structures were proposed based on their MS/MS fragmentation patterns. A plausible spb biosynthetic pathway was proposed. To the best of our knowledge, this is the first report of the isolation of desferrioxamines from the actinobacterial genus Kribbella .

Dermacoccus abyssi strain MT1.1 T is a piezotolerant actinobacterium that was isolated from Mariana Trench sediment collected at a depth of 10898 m. The organism was found to produce ten dermacozines (A‒J) that belonged to a new phenazine family and which displayed various biological activities such as radical scavenging and cytotoxicity. Here, we report on the isolation and identification of a new dermacozine compound, dermacozine M, the chemical structure of which was determined using 1D and 2D-NMR, and high resolution MS. A whole genome sequence of the strain contained six secondary metabolite-biosynthetic gene clusters (BGCs), including one responsible for the biosynthesis of a family of phenazine compounds. A pathway leading to the biosynthesis of dermacozines is proposed. Bioinformatic analyses of key stress-related genes provide an insight into how the organism adapted to the environmental conditions that prevail in the deep-sea.

The Atacama Desert of northern Chile is considered one of the most arid and extreme environment on Earth. Its core region was described as featuring "Mars-like" soils that were at one point deemed too extreme for life to exist. However, recent investigations confirmed the presence of diverse culturable actinobacteria. In the current review, we discuss a total of 46 natural products isolated to date representing diverse chemical classes characterized from different actinobacteria isolated from various locations in the Atacama Desert. Their reported biological activities are also discussed.

We report the structural characterization of a new pyrazinone analogue; butrepyrazinone, which was isolated from a new actinomycete strain Verrucosispora sp. K51G recovered from Ghanaian mangrove river sediment. Spectroscopy-guided fractionation led to the isolation of a compound from the fermentation culture and a combination of NMR spectroscopy, high-resolution mass spectrometry and computer-aided calculations revealed that butrepyrazinone (10) possesses an unusual methylation pattern on the pyrazinone ring. Butrepyrazinone (10), however, displayed no antibacterial activity against Gram-positive S. aureus ATCC 25923, the Gram-negative E. coli ATCC 25922 and a panel of clinical isolates of methicillin-resistant S. aureus (MRSA) strains, suggesting that 10 may act as a signal molecule for this strain. Although the same molecule has been synthesized previously, this is the first report to disclose the discovery of butrepyrazinone (10) from nature.

In this study, 137 actinomycetes were isolated from subtidal marine sediments in the North Pacific and Caribbean coasts of Costa Rica. Bioinformatics analysis of the 16S rRNA gene sequences assigned the isolates to 15 families and 21 genera. Streptomyces was the dominant genus while the remaining 20 genera were poorly represented. Nearly 70% of the phylotypes presented a coastal-restricted distribution whereas the other 30% were common inhabitants of both shores. The coastal tropical waters of Costa Rica showed a high diversity of actinomycetes, both in terms of the number of species and phylogenetic composition, although significant differences were observed between and within shores. The observed pattern of species distribution might be the result of several factors including the characteristics of the ecosystems, presence of endemic species and the influence of terrestrial runoff.

Microorganisms are a valuable source of pharmaceutically active chemicals, serving as scaffolds for synthesis as well as lead structures. Investigating novel biomes frequently yields intriguing chemistry; the Atacama Desert in Chile is one such example. This study reports the isolation of a new reduced anthracycline-related compound from the Atacama Desert-derived bacterium Saccharothrix S26. Structural characterisation was achieved by one-dimensional and two-dimensional NMR, HR-LCMS, and X-ray crystallography. The compound was tested against the ESKAPE pathogens, bovine mastitis-related pathogens, and the fungal strain Cryptococcus neoformans, but no antimicrobial activity was observed. [ABSTRACT FROM AUTHOR]

In this paper, we report on the chemistry of the rare South African Actinomycete Kribbella speibonae strain SK5, a prolific producer of hydroxamate siderophores and their congeners. Two new analogues, dehydroxylated desferrioxamines, speibonoxamine 1 and desoxy-desferrioxamine D12, have been isolated, together with four known hydroxamates, desferrioxamine D13, desferrioxamine B 4, desoxy-nocardamine 5 and nocardamine 6, and a diketopiperazine (DKP) 7. The structures of 1–7 were characterized by the analysis of HRESIMS and 1D and 2D NMR data, as well as by comparison with the relevant literature. Three new dehydroxy desferrioxamine derivatives 8–10 were tentatively identified in the molecular network of K.speibonae strain SK5 extracts, and structures were proposed based on their MS/MS fragmentation patterns. A plausible spb biosynthetic pathway was proposed. To the best of our knowledge, this is the first report of the isolation of desferrioxamines from the actinobacterial genus Kribbella. [ABSTRACT FROM AUTHOR]

Abstract: Two new 16-membered macrolactone-type polyketides, Tianchimycin A (1) and B (2), were isolated from the rare actinomycete Saccharothrix xinjiangensis NRRL B-24321, together with one known compound, swalpamycin B (3). The isolated compounds were structurally characterized using 1D and 2D NMR and MS techniques. The antimicrobial activities of 1–3 were determined against a panel of Gram-negative and Gram-positive bacteria including five hospital isolates from NHS Grampian. Compound 3 displayed moderate antibacterial activity against three MRSA clinical isolates and Enterococcus faecalis ATCC 29212. [Copyright &y& Elsevier]