Antimicrobial Activity and Functional Genes of Actinobacteria from Coastal Wetland

Nocardiopsis codii sp. nov., and Rhodococcus chondri sp. nov., two novel actinomycetal species isolated from macroalgae collected in the northern Portuguese coast

Two novel actinomycetal strains, designated CC-R113T and CC-R104T, were isolated from the tissues of two macroalgae collected on the northern Portuguese coast. Phylogenetic analyses based on the 16S rRNA gene showed that strain CT-R113T belongs to the genus Nocardiopsis, being closely related to Nocardiopsis umidischolae 66/93T and Nocardiopsis tropica VKM Ac-1457T, with 98.65 and 98.39 % sequence similarity, respectively. The clade formed between the three type strains was confirmed by phylogenomic analysis. The genome of strain CT-R113T was 7.27 Mb in size with a G+C content of 71.3 mol %, with average nucleotide identity (ANI) values of 89.59 and 90.14 % with strains 66/93T and VKM Ac-1457T, respectively. The major cellular fatty acids were identified as C18 : 1  ω9c, iso-C16 : 0 and anteiso-C17 : 0. Menaquinone 10 (MK-10) was the major respiratory quinone. Comparative analysis of 16S rRNA gene sequences showed that strain CC-R104T belongs to the genus Rhodococcus and is most closely related to Rhodococcus pyridinivorans DSM 44555T, with 98.24 % sequence similarity. However, phylogenomic analysis revealed that strain CC-R104T establishes a clade with Rhodococcus artemisae DSM 45380T, being more distant from Rhodococcus pyridinivorans DSM 44555T. The genome of strain CC-R104T was 5.34 Mb in size with a G+C content of 67.01 mol%. The ANI value between strains CC-R104T and DSM 45380T was 81.2 % and between strains CC-R104T and DSM 44555T was 81.5 %. The major cellular fatty acids were identified as C18 : 1  ω9c, C16 : 0 and summed feature 3. Menaquinone 8 (MK-8) was the only respiratory quinone. For both CC-R113T and CC-R104T, optimum growth was observed at pH 7.0, 28 °C and 0-5 % NaCl and whole-cell hydrolysates contained meso-diaminopimelic acid as the cell-wall diamino acid. On the basis of phenotypic, molecular and chemotaxonomic characteristics, strains CT-R113T and CC-R104T are considered to represent novel species, for which the names Nocardiopsis codii sp. nov. (type strain CT-R113T=LMG33234T=UCCCB172T) and Rhodococcus chondri sp. nov. (type strain CC-R104T=LMG33233T=UCCCB171T) are proposed.

Genus Nocardiopsis: A Prolific Producer of Natural Products

Actinomycetes are currently one of the major sources of bioactive secondary metabolites used for medicine development. Accumulating evidence has shown that Nocardiopsis, a key class of actinomycetes, has the ability to produce novel bioactive natural products. This review covers the sources, distribution, bioactivities, biosynthesis, and structural characteristics of compounds isolated from Nocardiopsis in the period between March 2018 and 2021. Our results reveal that 67% of Nocardiopsis-derived natural products are reported for the first time, and 73% of them are isolated from marine Nocardiopsis. The chemical structures of the Nocardiopsis-derived compounds have diverse skeletons, concentrating on the categories of polyketides, peptides, terphenyls, and alkaloids. Almost 50% of the natural products isolated from Nocardiopsis have been discovered to display various bioactivities. These results fully demonstrate the great potential of the genus Nocardiopsis to produce novel bioactive secondary metabolites that may serve as a structural foundation for the development of novel drugs.