ABSTRACT
A novel bacterial strain A7.6T was isolated from the sediments collected near the Zhairuo Island located in the East China Sea and characterized using a polyphasic approach. Cells were Gram-stain-negative, rod-shaped, non-spore forming, non-flagellated but motile by gliding. The strain was aerobic, positive for oxidase and catalase activities. The strain can grow at 4-35 °C, pH 5.5-9.0, and 0-3% (w/v) NaCl concentration. The major polar lipid was phosphatidylethanolamine, the predominant fatty acids (> 10%) were iso-C15:0 and summed feature 3 (C16:1 ω7c and/or C16:1 ω6c). The genomic G+C content was 33.6 mol% and the major respiratory quinone was menaquinone 6. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain A7.6T belonged to the genus Flavobacterium and was closely related to Flavobacterium tistrianum GB 56.1T (98.4% similarity), F. nitrogenifigens NXU-44T (98.4%), F. ginsenosidimutans THG 01T (98.0%) and F. anhuiense D3T (97.7%). Average nucleotide identities and digital DNA-DNA hybridizations values for genomes ranged from 75.9 to 91.4% and 21.4 to 43.9% between strain A7.6T and its closest phylogenetic neighbors. The polyphasic characterization indicated that strain A7.6T represented a novel species of the genus Flavobacterium, for which the name Flavobacterium sharifuzzamanii is proposed. The type strain is A7.6T (= KCTC 62405T = MCCC 1K03485T). The NCBI GenBank accession number for the 16S rRNA gene of A7.6T is MH396692, and for the genome sequence is QJGZ00000000. The digital protologue database (DPD) Taxon Number is TA00643.
Subject(s)
Flavobacterium/classification , Flavobacterium/physiology , Geologic Sediments/microbiology , Oceans and Seas , Phylogeny , Base Composition , China , DNA, Bacterial/genetics , Fatty Acids/analysis , Flavobacterium/chemistry , Genome, Bacterial/genetics , Hydrogen-Ion Concentration , Phospholipids/analysis , Quinones/analysis , RNA, Ribosomal, 16S/genetics , Sequence Analysis, DNA , Sodium Chloride , TemperatureABSTRACT
A new bacterial strain, designated 452T, was isolated from the rhizosphere soil of the mangrove Avicennia marina in China. As determined, its cell wall peptidoglycan contained LL-diaminopimelic acid; MK-9(H8) and MK-9(H6) were the major isoprenoid quinones; and iso-C16:0 (31.3%), anteiso-C15:0 (16.9%), and iso-C15:0 (12.5%) were the major cellular fatty acids (>10.0%). Phylogenetic analysis based on the 16S rRNA gene sequence revealed that strain 452T formed a distinct lineage in the clade of the genus Streptomyces, and was closely related to S. coerulescens DSM 40146T (99.6% sequence identity), S. bellus DSM 40185T (99.5%), and S. coeruleorubidus DSM 41172T (99.3%). The DNA-DNA relatedness between strain 452T and these type strains ranged between 29.3 and 42.3%. Based on the phenotypic, chemotaxonomic, and phylogenetic features, the strain 452T is considered to represent a novel species of the genus Streptomyces, for which the name Streptomyces nigra sp. nov. is proposed. The type strain is 452T (=KCTC 39960T = MCCC 1K03346T). Further, strain 452T extracts exhibited a pronounced antitumor activity against human cancer cell lines A549, HCT-116, and HepG2, but not against normal human colon cells CCD-18Co. Active substances in the fermentation broth of strain 452T were isolated by bioassay-guided analysis, and then purified using a macroporous resin, silica gel, sephadex LX-20 column, and semi-preparative high-performance liquid chromatography (HPLC). Eight proline-containing diketopiperazines, namely, cyclo(Pro-Ala), cyclo(Pro-Gly), cyclo(Pro-Phe), cyclo(Pro-Met), cyclo(Pro-Val), cyclo(Pro-Leu), cyclo(Pro-Tyr), and cyclo(L-Leu-trans-4-hydroxy-L-Pro), were identified by electrospray ionization mass spectrometry (MS) and nuclear magnetic resonance (NMR). The compounds displayed different levels of cytotoxicity. The highest cytotoxicity was exhibited by cyclo(Pro-Ala) and cyclo(Pro-Met) against A549 cells, and cyclo(Phe-Pro) and cyclo(Pro-Ala) against HCT-116 cells, with average IC50 values equal to 18.5, 27.3, 32.3, and 47.6 µg/mL, respectively. The diversity of diketopiperazines and other chemicals produced by 452T was further investigated using gas chromatography (GC)-MS and liquid chromatography (LC)-MS. The analysis revealed 16 types of metabolites with antitumor activity and 16 other types of diketopiperazines. Hence, extracts of the newly identified strain may be used a starting material for the development of antitumor agents.
