Description of six novel species Bacillus bruguierae sp. nov., Bacillus kandeliae sp. nov., Bacillus yunxiaonensis sp. nov., Metabacillus rhizosphaerae sp. nov., Metabacillus sediminis sp. nov. and Psychrobacillus mangrovi sp. nov., isolated from mangrove ecosystem

Six Gram-stain-positive and rod-shaped strains, designated FJAT-51614T, FJAT-51639T, FJAT-52054T, FJAT-52991T, FJAT-53654T and FJAT-53711T, were isolated from a mangrove ecosystem. The condition for growth among the strains varied (pH ranging 5.0-11.0 and temperature 15-45 °C). These strains showed the highest 16S rRNA gene sequence similarity to the genera Bacillus, Metabacillus and Psychrobacillus. Menaquinone MK-7 (100%) was present in all strains except strain FJAT-51614T, which contained MK-7 (32%) and MK-8 (68%). The major fatty acids (>10%) in strains FJAT-52054T and FJAT-51614T were anteiso-C15 : 0 and iso-C14 : 0. The major fatty acid (>10%) in strain FJAT-53654T was anteiso-C15 : 0, while in strain FJAT-51639T were iso-C15 : 0 and iso-C17 : 0. The major fatty acids in strains FJAT-52991T and FJAT-53711T were iso-C15 : 0 and iso-C16 : 0. The major polar lipids in strains FJAT-51639T, FJAT-52991T and FJAT-51614T were diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine, while strains FJAT-53711T, FJAT-52054T and FJAT-53654T consist of diphosphatidylglycerol and phosphatidylglycerol. The genome-relatedness values among the present study strains and the closest species were below the recognized cutoff levels for species delineation. The polyphasic analysis comparison results represent six strains as novel species for which the names Bacillus bruguierae sp. nov. (FJAT-51639T=GDMCC 1.3073T=JCM 35615T), Bacillus kandeliae sp. nov. (FJAT-52991T=GDMCC 1.3069T=JCM 35619T), Bacillus yunxiaonensis sp. nov. (FJAT-53711T=GDMCC 1.3068T=JCM 35616T), Metabacillus rhizosphaerae sp. nov. (FJAT-53654T=GDMCC 1.3075T=JCM 35614T), Metabacillus sediminis sp. nov. (FJAT-52054T=GDMCC 1.3074T=JCM 35620T) and Psychrobacillus mangrovi sp. nov. (FJAT-51614T=GDMCC 1.3072T=JCM35478T) are proposed.

Characterization and Bioactive Metabolite Profiling of Streptomyces sp. Y009: A Mangrove-Derived Actinomycetia with Anticancer and Antioxidant Potential

Microorganisms from poorly explored environments are promising sources for the development of novel drugs. In our continuous efforts to screen for mangrove actinomycetes that produce metabolites with potential pharmaceutical applications, Streptomyces sp. Y009 was isolated from mangrove sediments in Guangxi, China. The phenotypic, physiological, biochemical, and phylogenetic characteristics of this strain were investigated. Analysis of phylogenetic and 16S rRNA gene sequences showed that it had the highest sequence similarity to Streptomyces thermolilacinus NBRC 14274 (98.95%). Further, the Y009 extract exhibited antioxidant activity, as indicated by DPPH and superoxide dismutase assays. The extract showed broad-spectrum and potent anticancer potential against six human cancer cell lines, with IC50 values ranging from 5.61 to 72.15 μg/mL. Furthermore, the selectivity index (SI) demonstrated that the Y009 extract exhibited less toxicity toward normal cell lines in comparison to the lung cancer cell line (A549) and hepatoma cell line (HepG2). GC-MS analysis revealed that the extract contained some biologically important secondary metabolites, mainly cyclic dipeptides and esters, which might be responsible for the antioxidant and anticancer properties. 3-Isobutylhexahydropyrrolo[1,2-a]pyrazine-1,4-dione (28.32%) was the major chemical compound available in the extract. The effect on cancer cells was then confirmed using nuclear staining and in silico docking. This study suggests that further exploration of the bioactive compounds of the newly isolated strain may be a promising approach for the development of novel chemopreventive drugs.

Streptomyces chengmaiensis sp. nov., isolated from the stem of a mangrove plant in Hainan

A novel Streptomyces strain, designated as HNM0663T, was isolated from the stem of a mangrove plant (Avicennia marina) collected from the coast of Chengmai city, Hainan Island, PR China. On the basis of the alignment of 16S rRNA gene sequences, strain HNM0663T was closely related to Streptomyces lichenis LCR6-01T (98.67 %), Streptomyces nanningensis YIM 33098T (98.12 %) and Streptomyces palmae CMU-AB204T (97.93 %). Genome-based comparisons showed that strain HNM0663T was distinguished from its closest related species with 80.3 % average nucleotide identity and 20.2 % digital DNA-DNA hybridization values. The main cellular fatty acids were iso-C16 : 0, iso-C15 : 0 and anteiso-C15 : 0. The main menaquinones were MK-9 (H6), MK-9 (H4) and MK-8 (H4). The predominant phospholipids contained diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and phosphatidylcholine. Based on these polyphasic taxonomy results, strain HNM0663T should represent a novel Streptomyces species, for which the name Streptomyces chengmaiensis sp. nov. is proposed. The type strain is HNM 0663T (=CCTCC AA 2019075T=LMG 31909T).

Streptomyces musisoli sp. nov., an actinomycete isolated from soil

An actinobacterium, strain CH5-8^T, which formed spiral chains of spore arising from the aerial mycelium, was isolated from rhizosphere soil of Musa spp. The organism exhibited vivid greenish yellow substrate mycelium and easily produced the medium grey aerial spore mass on ISP2 medium. The typical chemotaxonomic properties of members of the genus Streptomyces were observed for strain CH5-8^T, e.g. ll-diaminopimelic acid in cell peptidoglycan, MK-9(H₈), MK-9(H₆), and MK-9(H₄) as major menaquinones and anteiso-C_15 : 0, iso-C_16 : 0, and anteiso-C_17 : 0 as major fatty acids. Diphosphatidylglycerol, phosphatidylethanolamine, hydroxyphosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol and phosphatidylinositol mannoside were detected in the cells. A combination of morphological and chemotaxonomic data supported the assignment to the genus Streptomyces. The analysis result obtained for the 16S rRNA gene sequence confirmed the taxonomic affiliation at the genus level of this strain. The novel strain CH5-8^T showed the highest 16S rRNA gene sequence values to Streptomyces echinatus NBRC 12763^T (98.9 %), followed by Streptomyces actinomycinicus RCU-197^T (98.9 %). The average nucleotide identity by blast (ANIb) and digital DNA-DNA hybridization values between CH5-8^T and its closest relatives, S. echinatus CECT 3313^T and S. actinomycinicus RCU-197^T, were ≤91.6 % and ≤47.4 %, respectively. The digital DNA G+C content of genomic DNA was 72.1 mol%. On the basis of these phenotypic and genotypic data, strain CH5-8^T represents a novel species, for which the name Streptomyces musisoli sp. nov. is proposed. The type strain is CH5-8^T (=TBRC 9950^T=NBRC 113997^T).