Nocardiopsis oceani sp. nov. and Nocardiopsis nanhaiensis sp. nov., actinomycetes isolated from marine sediment of the South China Sea

Comprehensive updates on the biological features and metabolic potential of the versatile extremophilic actinomycete Nocardiopsis dassonvillei

Nocardiopsis dassonvillei prevails under harsh environmental conditions and the purpose of this review is to highlight its biological features and recent biotechnological applications. The organism prevails in salt-rich soils/marine systems and some strains endure extreme temperatures and pH. A few isolates are associated with marine organisms and others cause human diseases. Comparative genomic analysis indicates its versatility in producing biotechnologically relevant metabolites. Antimicrobial, cytotoxic, anticancer and growth promoting biomolecules are obtained from this organism. It also synthesizes biotechnologically important enzymes. Bioactive compounds and enzymes obtained from this actinomycete provide evidence regarding its metabolic competence and its potential economic value.

Nocardiopsis changdeensis sp. nov., an endophytic actinomycete isolated from the roots of Eucommia ulmoides Oliv

Strain Mg02T was isolated from roots of Eucommia ulmoides Oliv. collected from Changde City, Hunan Province, China. Strain Mg02T, which exhibited distinct chemotaxonomic characteristics of the genus Nocardiopsis: cell-wall chemotype III/C, i.e., meso-diaminopimelic acid as diagnostic amino acid in whole-cell hydrolysates and menaquinone MK-10 with variable degrees of saturation in the side chain as the predominant isoprenoid quinone, was investigated by a polyphasic approach to determine their taxonomic position. Sequence analysis of the 16S rRNA gene indicated that strain Mg02T is affiliated to the genus Nocardiopsis, having highest sequence similarity to Nocardiopsis flavescens CGMCC 4.5723T (99.1%) and <98.7% to other species of the genus Nocardiopsis with validly published names. Phylogenetic analysis of 16S rRNA gene indicated strain Mg02T formed a separate evolutionary clade, suggesting that it could be a novel Nocardiopsis species. Phylogenomic analysis showed that strain Mg02T was closely related to N. flavescens CGMCC 4.5723T and distinct from the latter according to the clustering patterns. The Average Nucleotide Identity and digital DNA-DNA hybridization values between strain Mg02T and N. flavescens CGMCC 4.5723T were far below the species-level thresholds. Based on phenotypic, phylogenetic and chemotaxonomic characteristics, we think that strain Mg02T should represent a novel Nocardiopsis species, for which the name Nocardiopsis changdeensis sp. nov. is proposed. The type strain is Mg02T (=MCCC 1K06174T = JCM 34709T).

Nocardiopsis eucommiae sp. nov., a novel endophytic actinomycete isolated from leaves of Eucommia ulmoides Oliv

A novel Gram-stain-positive, endophytic actinobacterium, designated strain HDS5^T, was isolated from leaves of Eucommia ulmoides Oliv. collected from Changde City, Hunan Province, PR China. Strain HDS5^T produced yellowish oil green substrate mycelia on Gause's synthetic medium, which also carried yellowish oil green aerial hyphae, fragmenting into rod-shaped elements with smooth surfaces. Strain HDS5^T grew at pH 5.0-11.0 (optimum, pH 7), at 20-40 °C (optimum, 28 °C) and in the presence of 0-8.0% NaCl (w/v; optimum, 0-1.0 %). Whole-cell hydrolysates contained meso-diaminopimelic acid as the diagnostic amino acid and no diagnostic sugars. The predominant fatty acids were iso-C_16:0 and C_18 : 1 ω9c. The menaquinones were MK-10(H₂), MK-10(H₄) and MK-10(H₆). Strain HDS5^T showed high 16S rRNA gene sequence similarity to Nocardiopsis prasina DSM 43845^T (99.72 %), Nocardiopsis ganjiahuensis DSM 45031^T (99.31 %), Nocardiopsis exhalans JCM 11759^T (99.17 %), Nocardiopsis alba DSM 43377^T (99.11 %), Nocardiopsis metallicus KBS6^T (99.11 %), Nocardiopsis valliformis DSM 45023^T (99.04 %), Nocardiopsis listeri NBRC 13360^T (98.97 %), Nocardiopsis lucentensis DSM 44048^T (98.83 %), Nocardiopsis terrae YIM 90022^T (98.83 %) and <98.7 % similarities to other type strains. Phylogenetic analysis of 16S rRNA gene sequences and whole-genome sequences showed that strain HDS5^T was closely related to N. prasina DSM 43845^T. However, the average nucleotide identity based on blast and digital DNA-DNA hybridization values between them were determined to be 90.1 and 40.9 %, respectively, below the threshold of 95-96 and 70 % for the delineation of prokaryotic genomic species, suggesting that strain HDS5^T represents a novel Nocardiopsis species. Furthermore, the morphological and physio-biochemical characteristics were sufficient to distinguish strain HDS5^T from N. prasina DSM 43845^T. Consequently, based on phenotypic and genotypic characteristics, strain HDS5^T represents a new Nocardiopsis species, for which the name Nocardiopsis eucommiae sp. nov. is proposed. The type strain is HDS5^T (=MCCC 1K06172^T=JCM 34707^T).

Nocardiopsis dassonvillei subsp. crassaminis subsp. nov., isolated from freshwater sediment, and reappraisal of Nocardiopsis alborubida Grund and Kroppenstedt 1990 emend. Nouioui et al. 2018

An actinomycete, strain D1^T, was isolated from a freshwater sediment sample collected from the San Pablo river in the La Risueña community, Santiago de Cuba province, Cuba. The strain was identified as a member of the genus Nocardiopsis by means of a polyphasic taxonomic study. It produced a light yellow non-fragmented substrate mycelium, a white well-developed aerial mycelium and straight to flexuous hyphae. No specific spore chains were observed. Strain D1^T contained meso-diaminopimelic acid, no diagnostic sugars, and MK-10(H₂), MK-10(H₄), MK-10 and MK-10(H₆) as predominant menaquinones, but not phosphatidylcholine as diagnostic polar lipid of the genus Nocardiopsis. The predominant fatty acids were iso-C_16 : 0, 10-methyl-C_18 : 0 and anteiso-C_17 : 0. Strain D1^T showed the highest degree of 16S rRNA gene sequence similarity to Nocardiopsis synnematoformans DSM 44143^T (99.8 %), Nocardiopsis dassonvillei subsp. albirubida NBRC 13392^T (99.8 %) and Nocardiopsis dassonvillei subsp. dassonvillei DSM 43111^T (99.6 %). A genomic OrthoANIu value between D1^T and N. dassonvillei subsp. dassonvillei DSM 43111^T of 97.63 % and a dDDH value of 78.9 % indicated that strain D1^T should be classified in N. dassonvillei. However, phenotypic characteristics distinguished strain D1^T from its nearest neighbour taxon. On basis of these results we propose to classify strain D1^T (=LMG 30468^T=CECT 30033^T) as a representative of a novel subspecies of the genus Nocardiopsis, for which the name Nocardiopsis dassonvillei subsp. crassaminis subsp. nov. is proposed. In addition, the genomic distance between N. dassonvillei subsp. albirubida NBRC 13392^T and N. dassonvillei subsp. dassonvillei DSM 43111^T as determined through OrthoANIu (93.64 %) and dDDH (53.40 %), along with considerable phenotypic and chemotaxonomic differences reported in earlier studies, indicated that the classification of this taxon as Nocardiopsis alborubida Grund and Kroppenstedt 1990 is to be preferred over its classification as N. dassonvillei subsp. albirubida Evtushenko et al. 2000.

Marine Rare Actinomycetes: A Promising Source of Structurally Diverse and Unique Novel Natural Products

Rare actinomycetes are prolific in the marine environment; however, knowledge about their diversity, distribution and biochemistry is limited. Marine rare actinomycetes represent a rather untapped source of chemically diverse secondary metabolites and novel bioactive compounds. In this review, we aim to summarize the present knowledge on the isolation, diversity, distribution and natural product discovery of marine rare actinomycetes reported from mid-2013 to 2017. A total of 97 new species, representing 9 novel genera and belonging to 27 families of marine rare actinomycetes have been reported, with the highest numbers of novel isolates from the families Pseudonocardiaceae, Demequinaceae, Micromonosporaceae and Nocardioidaceae. Additionally, this study reviewed 167 new bioactive compounds produced by 58 different rare actinomycete species representing 24 genera. Most of the compounds produced by the marine rare actinomycetes present antibacterial, antifungal, antiparasitic, anticancer or antimalarial activities. The highest numbers of natural products were derived from the genera Nocardiopsis, Micromonospora, Salinispora and Pseudonocardia. Members of the genus Micromonospora were revealed to be the richest source of chemically diverse and unique bioactive natural products.

Transcriptomic and Ectoine Analysis of Halotolerant Nocardiopsis gilva YIM 90087T Under Salt Stress

The genus Nocardiopsis is an unique actinobacterial group that widely distributed in hypersaline environments. In this study, we investigated the growth conditions, transcriptome analysis, production and accumulation of ectoine by Nocardiopsis gilva YIM 90087^T under salt stress. The colony color of N. gilva YIM 90087^T changed from yellow to white under salt stress conditions. Accumulation of ectoine and hydroxyectoine in cells was an efficient way to regulate osmotic pressure. The ectoine synthesis was studied by transferring the related genes (ectA, ectB, and ectC) to Escherichia coli. Transcriptomic analysis showed that the pathways of ABC transporters (ko02010) and glycine, serine, and threonine metabolism (ko00260) played a vital role under salt stress environment. The ectABC from N. gilva YIM 90087^T was activated under the salt stress. Addition of exogenous ectoine and hydroxyectoine were helpful to protect N. gilva YIM 90087^T from salt stress.

Nocardiopsissediminis sp. nov., isolated from mangrove sediment

A filamentous actinomycete, designated strain 1SS5-02T, was isolated from mangrove sediment collected from Ranong province, Thailand. The strain formed aerial and substrate mycelia composed of long, branched hyphae. Aerial mycelia differentiated into non-motile, rod-shaped spores. The organism contained meso-diaminopimelic acid and no diagnostic sugars in whole-cell hydrolysates. The predominant menaquinones were MK-11(H4), MK-11(H6) and MK-11(H8). Polar lipids comprised phosphatidylcholine, phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, two unidentified phospholipids and four unidentified lipids. The major fatty acids were iso-C16 : 0, C18 : 1ω9c, 10-methyl C18 : 0 and anteiso-C17 : 0. The G+C content of the genomic DNA was 73.5 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain 1SS5-02T belonged to the genus Nocardiopsis. The strain showed the highest degree of 16S rRNA gene sequence similarity with 'Nocardiopsis mangrovei' HA11166 (97.9 %) and Nocardiopsis trehalosi VKM Ac-942T (97.8 %). However, strain 1SS5-02T could be distinguished from its nearest phylogenetic relatives in the genus Nocardiopsis on the basis of DNA-DNA relatedness values and the combination of phenotypic properties. On the basis of polyphasic taxonomy, strain 1SS5-02T is considered to represent a novel species of the genus Nocardiopsis, for which the name Nocardiopsis sediminis sp. nov. is proposed. The type strain is 1SS5-02T (=BCC 75410T=NBRC 110934T).

Nocardiopsis ansamitocini sp. nov., a new producer of ansamitocin P-3 of the genus Nocardiopsis

An alkalitolerant actinomycete strain, designated EGI 80425T, capable of producing ansamitocin P-3, was isolated from a saline-alkali soil sample of Xinjiang province, north-west China, and subjected to a polyphasic taxonomic characterization. Strain EGI 80425T formed non-fragmented substrate mycelia and white aerial hyphae with long spore chains. Whole-cell hydrolysates of the isolate contained meso-diaminopimelic acid as the diagnostic diamino acid and rhamnose as the major sugar. The major fatty acids were anteiso-C17 : 0, iso-C16 : 0 and C18 : 1ω9c. The predominant menaquinones were MK-10(H4), MK-10(H6), MK-10(H8) and MK-9(H4). The G+C content of the genomic DNA of strain EGI 80425T was 70.2 mol%. Strain EGI 80425T showed highest 16S rRNA gene sequence similarity to Nocardiopsis dassonvillei subsp. dassonvillei DSM 43111T (96.44 %). Phylogenetic analysis showed that strain EGI 80425T clustered with the members of the genus Nocardiopsis. Based on phenotypic, chemotaxonomic and phylogenetic characteristics, strain EGI 80425T represents a novel species of the genus Nocardiopsis, for which the name Nocardiopsis ansamitocini sp. nov. is proposed. The type strain is EGI 80425T ( = CGMCC 9969T = KCTC 39605T).