Actinomadura graeca sp. nov.: A novel producer of the macrocyclic antibiotic zelkovamycin.

As part of a screening programme for antibiotic-producing bacteria, a novel Actinomadura species was discovered from a soil sample collected in Santorini, Greece. Preliminary 16S rRNA gene sequence comparisons highlighted Actinomadura macra as the most similar characterised species. However, whole-genome sequencing revealed an average nucleotide identity (ANI) value of 89% with A. macra, the highest among related species. Further phenotypic and chemotaxonomic analyses confirmed that the isolate represents a previously uncharacterised species in the genus Actinomadura, for which the name Actinomadura graeca sp. nov. is proposed (type strain 32-07T). The G+C content of A. graeca 32-07 is 72.36%. The cell wall contains DL-diaminopimelic acid, intracellular sugars are glucose, ribose and galactose, the predominant menaquinone is MK-9(H6), the major cellular lipid is phosphatidylinositol and fatty acids consist mainly of hexadecanoic acid. No mycolic acid was detected. Furthermore, A. graeca 32-07 has been confirmed as a novel producer of the non-ribosomal peptide antibiotic zelkovamycin and we report herein a provisional description of the unique biosynthetic gene cluster.

Actinomadura decatromicini sp. nov., isolated from mountain soil in Thailand.

A novel actinomycete strain CYP1-5T was isolated from the mountain soil sample collected from Chaiyaphum province, Thailand and its taxonomic position was clarified by using a polyphasic taxonomic approach. The chemotaxonomic properties of strain CYP1-5T were consistent within the genus Actinomadura. Cell-wall peptidoglycan of this strain contained meso-diaminopimelic acid. Galactose, madurose, and ribose were presented as the diagnostic sugars in whole-cell hydrolysates. The major menaquinone was MK-9(H6). Major cellular fatty acids were iso-C16:0 and C16:0. Phosphatidylglycerol, diphosphatidylglycerol, phosphatidylinositol, and phosphatidylinositol mannoside were observed as predominant phospholipids. Based on the results of phylogenetic analyses of 16S rRNA gene sequence, strain CYP1-5T was constituent with the genus Actinomadura and was closely related to Actinomadura syzygii GKU157T (99.5%) and Actinomadura chibensis IFM 10266T (= JCM 14158T) (98.2%). The draft genome size of strain CYP1-5T was 9.30 Mb with 72.2 mol% of G + C content. Strain CYP1-5T showed ANIb values of 94.9% with A. syzygii GKU157T and 93.2% with A. chibensis JCM 14158T. Phenotypic characteristics, phylogenetic analysis and genome data support that strain CYP1-5T could be discriminated from its closest relatives, representing a novel species of the genus Actinomadura, for which the name Actinomadura decatromicini sp. nov. is proposed. The type strain is CYP1-5T (= JCM 16996T = KCTC 19916T = TISTR 2901T).

Gene Cluster Activation in a Bacterial Symbiont Leads to Halogenated Angucyclic Maduralactomycins and Spirocyclic Actinospirols.

Growth from spores activated a biosynthetic gene cluster in Actinomadura sp. RB29, resulting in the identification of two novel groups of halogenated polyketide natural products, named maduralactomycins and actinospirols. The unique tetracyclic and spirocyclic structures were assigned based on a combination of NMR analysis, chemoinformatic calculations, X-ray crystallography, and 13C labeling studies. On the basis of HRMS2 data, genome mining, and gene expression studies, we propose an underlying noncanonical angucycline biosynthesis and extensive post-polyketide synthase (PKS) oxidative modifications.

Actinomycetoma Caused by Actinomadura mexicana, A Neglected Entity in the Caribbean.

Mycetoma is a chronic infection that is slow to develop and heal. It can be caused by fungi (eumycetoma) or bacteria (actinomycetoma). We describe a case of actinomycetoma caused by Actinomadura mexicana in the Caribbean region.