Yongqiang Tian

Comparative analysis of chemical constituents, antimicrobial and antioxidant activities of ethylacetate extracts of Polygonum cuspidatum and its endophytic actinomycete, Streptomyces sp. A0916

The present study investigated the chemical composition of ethylacetate extracts from an endophytic actinomycete Streptomyces sp. A0916 and its host Polygonum cuspidatum. A comparative analysis of the antimicrobial and antioxidant properties of the extracts was also conducted. 32 compounds of P. cuspidatum and 23 compounds of Streptomyces sp. A0916 were isolated and identified by GC/MS. Antimicrobial activities of the extracts were evaluated using eight microbial strains (3 Gram-positive bacteria, 3 Gram-negative bacteria, and 2 fungi). The Streptomyces sp. A0916 extracts showed a wide range of antimicrobial activities and presented greater antimicrobial effectiveness than the P. cuspidatum extracts. The minimum inhibitory concentration (MIC) of Streptomyces sp. A0916 extracts against the ampicillin-resistant strain Enterococcus faecium SIIA843 was 32 μg·mL(-1). Furthermore, the extracts had greater antimicrobial effect against Gram-positive bacteria than Gram-negative bacteria. Finally, the antioxidant activity of the Streptomyces sp. A0916 extracts was equal to that of the P. cuspidatum extracts. In conclusion, our results suggest that the endophytic actinomycetes of the medicinal plants are an important source of bioactive substances.

Diversity, bioactivities, and metabolic potentials of endophytic actinomycetes isolated from traditional medicinal plants in Sichuan, China

The present study was designed to determine the taxonomic diversity and metabolic activity of the actinomycetes community, including 13 traditional medicinal plants collected in Sichuan province, China, using multiple approaches such as morphological and molecular identification methods, bioactivity assays, and PCR screening for genes involved in antibiotics biosynthesis. 119 endophytic actinomycetes were recovered; 80 representative strains were chosen for 16S rRNA gene partial sequence analyses, with 66 of them being affiliated to genus Streptomyces and the remaining 14 strains being rare actinomycetes. Antimicrobial tests showed that 12 (15%) of the 80 endophytic actinomycetes displayed inhibitory effects against at least one indicator pathogens, which were all assigned to the genus Streptomyces. In addition, 87.5% and 58.8% of the isolates showed anticancer and anti-diabetic activities, respectively. Meanwhile, the anticancer activities of the isolates negatively correlated with their anti-diabetic activities. Based on the results of PCR screening, five genes, PKS-I, PKS-II, NRPS, ANSA, and oxyB, were detected in 55.0%, 58.8%, 90.0%, 18.8% and 8.8% of the 80 actinomycetes, respectively. In conclusion, the PCR screening method employed in the present study was conducive for screening and selection of potential actinomycetes and predicting potential secondary metabolites, which could overcome the limitations of traditional activity screening models.

Corrigendum: Characterization of Trichococcus paludicola sp. nov. and Trichococcus alkaliphilus sp. nov., isolated from a high-elevation wetland, by phenotypic and genomic analyses.

Two psychrotolerant facultative anaerobes, strains B7-2T and B5T, were isolated from the Zoige Wetland on the Qinghai-Tibetan Plateau. The 16S rRNA gene sequences of strains B7-2T and B5T shared high similarity (>99u200a%) with those of the type strains of the genus Trichococcus, while their digital DNA-DNA hybridization values with each other (49u200a%) and with the reference type strains (48-23u200a%) were lower than 70u200a%, which suggest that they represent two novel species of the genus Trichococcus. Cells of strains B7-2T and B5T were immotile cocci, grew in the temperature range of 4-37u2009°C (optimum 25u2009°C) and were alkaliphilic with optimum growth at pH 9.0. The major components of the cellular fatty acids were C16u200a:u200a0, anteiso-C17u200a:u200a0 and C18u200a:u200a0 for strain B7-2T, and C16u200a:u200a0, anteiso-C17u200a:u200a0, C18u200a:u200a1ω9c and C18u200a:u200a0 for strain B5T. The genomic DNA G+C contents were 46.0 and 46.7u2009mol% for strains B7-2T and B5T, respectively. Based on physiological and genomic characteristics, it is suggested that strains B7-2T and B5T represent two novel species within the genus Trichococcus, for which the names Trichococcus paludicola sp. nov. and Trichococcus alkaliphilus sp. nov. are proposed. The type strains are B7-2T (=DSM 104691T=KCTC 33886T) and B5T (=DSM 104692T=KCTC 33885T), respectively.

Biosynthesis, characterization and antimicrobial activity of silver nanoparticles by a halotolerant Bacillus endophyticus SCU-L

Abstract We have conducted a thorough study on extracellular biosynthesis of silver nanoparticles (AgNPs) by a halotolerant bacterium Bacillus endophyticus SCU-L, which was identified by 16S rRNA gene sequencing analysis. This strain was selected during an ongoing research programme aimed at finding a novel biological method for green nanosynthetic routes using the extremophiles in unexplored hypersaline habitats. The biosynthesized AgNPs were characterized and analyzed with UV–vis spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, atomic force microscopy and X-ray diffraction. Further, the AgNPs were found to be spherical in shape with an average particle size of about 5.1u2009nm, and it was stable in aqueous solution for three months period of storage at room temperature under dark condition. Also, the synthesized AgNPs significantly presented antimicrobial activity against Candida albicans, Escherichia coli, Salmonella typhi and Staphylococcus aureus. The above results suggested that the present work may provide a valuable reference and theoretical basis for further exploration on microbial biosynthesis of AgNPs by halotolerant bacteria.

Planococcus salinus sp. nov., a moderately halophilic bacterium isolated from a saline-alkali soil

A novel aerobic, Gram-stain-positive, motile, moderately halophilic and coccoid bacterial strain, designated LCB217T, was isolated from a saline-alkali soil in north-western China and identified using a polyphasic taxonomic approach. Growth occurred with 3-15u200a% (w/v) NaCl (optimum 3-5u200a%), at 10-45u2009°C (optimum 30u2009°C) and at pH 7.0-9.0 (optimum pH 9.0). Strain LCB217T contained MK-7 and MK-8 as the predominant menaquinones and anteiso-C15u200a:u200a0, iso-C14u200a:u200a0 and iso-C16u200a:u200a0 as the major fatty acids. The polar lipids from strain LCB217T consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, one unidentified phospholipid, one unidentified aminophospholipid and one unidentified lipid. The peptidoglycan type was A4α (l-Lys-d-Glu). Phylogenetic analysis of the 16S rRNA gene sequence showed that strain LCB217T belonged to the genus Planococcus and was closely related to the type strains Planococcus plakortidis AS/ASP6 (II)T (98.2u200a% similarity), Planococcus maitriensis S1T (97.7u200a%) and Planococcus salinarum ISL-16T (97.2u200a%). The G+Cu2009content of the genomic DNA was 49.4u2009mol%. DNA-DNA relatedness values between strain LCB217T andPlanococcusplakortidis AS/ASP6 (II)T, Planococcusmaitriensis S1T andPlanococcussalinarum ISL-16T were 29.5, 38.1 and 39.5u200a%, respectively. On the basis of the phenotypic, phylogenetic and genomic data, strain LCB217T represents a novel species of the genus Planococcus, for which the name Planococcus salinus sp. nov. is proposed. The type strain is LCB217T (=CGMCC 1.15685T=KCTC 33861T).

Regulatory genes and their roles for improvement of antibiotic biosynthesis in Streptomyces

The numerous secondary metabolites in Streptomyces spp. are crucial for various applications. For example, cephamycin C is used as an antibiotic, and avermectin is used as an insecticide. Specifically, antibiotic yield is closely related to many factors, such as the external environment, nutrition (including nitrogen and carbon sources), biosynthetic efficiency and the regulatory mechanisms in producing strains. There are various types of regulatory genes that work in different ways, such as pleiotropic (or global) regulatory genes, cluster-situated regulators, which are also called pathway-specific regulatory genes, and many other regulators. The study of regulatory genes that influence antibiotic biosynthesis in Streptomyces spp. not only provides a theoretical basis for antibiotic biosynthesis in Streptomyces but also helps to increase the yield of antibiotics via molecular manipulation of these regulatory genes. Currently, more and more emphasis is being placed on the regulatory genes of antibiotic biosynthetic gene clusters in Streptomyces spp., and many studies on these genes have been performed to improve the yield of antibiotics in Streptomyces. This paper lists many antibiotic biosynthesis regulatory genes in Streptomyces spp. and focuses on frequently investigated regulatory genes that are involved in pathway-specific regulation and pleiotropic regulation and their applications in genetic engineering.

Adaptations of Bacillus shacheensis HNA-14 required for long-term survival under osmotic challenge: a multi-omics perspective

Genomic sequence, transcriptomic, metabolomic and fatty acid analyses of strain HNA-14 were performed to understand the mechanism of salt tolerance for long-term survival. The results indicated that strain HNA-14 has different osmotic resistance mechanisms for long-term survival and short-term salt stress. The cells mainly synthesized compatible solutes to resist osmotic pressure when cultured under nutrient deficient conditions, while they can slow down the synthesis rate and uptake from the environment when cultured under a nutritionally rich environment. Also, the amounts of branched and unsaturated fatty acids in the cell membrane are maintained to a high degree (>50%) to maintain the fluidity of the cell membrane; when the cells are cultured in a high osmotic environment for long-term survival, they may increase the content of branched fatty acids and phosphoric fatty acids to increase the fluidity of the cell membrane to resist the high osmotic pressure.

Actinocorallia populi sp. nov., an endophytic actinomycete isolated from a root of Populus adenopoda (Maxim.)

An endophytic actinobacterium, strain A251T, was isolated from the root of Populus adenopoda Maxim and subjected to characterization using polyphasic taxonomy. Analysis of the 16S rRNA gene sequence revealed that the isolate represented a member of the phylogenetic cluster of the genus Actinocorallia and was most closely related to Actinocorallia aurantiaca JCM 8201T (98.0u200a%) and Actinocorallia libanotica IFO 10495T (98.0u200a%). DNA-DNA hybridization values between A251T and these strains were 41.2u200a% and 45.0u200a%, respectively. The G+Cu2009content of the DNA was 71.5u2009mol%. Major fatty acids were C16u200a:u200a0, C16u200a:u200a1ω7c and C18u200a:u200a1ω9c. The peptidoglycan diamino acid of A251T was meso-diaminopimelic acid and the whole-cell hydrolysates contained glucose and ribose. The major menaquinones were MK-9(H4) and MK-9(H6). The phospholipid profile included diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, an undefined aminophospholipid and two undefined phospholipids. DNA-DNA hybridization data in combination with differences in the biochemical and physiological properties, indicated that A251T should be classified as representing a novel species within the genus Actinocorallia, for which the name Actinocorallia populi sp. nov. is proposed, with A251T (=CGMCC 4.7421T=JCM 32178T) as the type strain.

Ornithinibacillus salinisoli sp. nov., a moderately halophilic bacterium isolated from a saline-alkali soil

A taxonomic study was performed on strain LCB256T, which was isolated from a saline-alkali soil sample taken from northwestern China. Cells of strain LCB256T were Gram-stain-positive, aerobic, rod-shaped and grew at 3-17u200a% (w/v) NaCl (optimum 10-15u200a%), 10-52u2009°C (optimum 25-30u2009°C) and pH 7.0-9.0 (optimum 8.0). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain LCB256T was most closely related to the two genera of Ornithinibacillus and Oceanobacillus, showing highest sequence similarity to Oceanobacillus limi KCTC 13823T (97.8u200a%) and Ornithinibacillus bavariensis WSBC 24001T (97.2u200a%). The peptidoglycan amino acid type was found to be A4β and the major respiratory quinone was determined to be MK-7. The polar lipid profile of strain LCB256T contained diphosphatidylglycerol, phosphatidylglycerol, one unidentified phospholipid and two unidentified aminolipids. The dominant cellular fatty acids were anteiso-C15u200a:u200a0 and iso-C15u200a:u200a0. The G+Cu2009content of genomic DNA was 39.3u2009mol%. DNA-DNA relatedness values between strain LCB256T and Ornithinibacillus halophilus KCTC 13822T and Oceanobacillus limi KCTC 13823T were 46.2 and 34.8u200a%, respectively. Based on this polyphasic taxonomic study, a novel species of the genus Ornithinibacillus, Ornithinibacillussalinisoli sp. nov. is proposed. The type strain is LCB256T (=CGMCC 1.15809T=KCTC 33862T).

Halomonas saliphila sp. nov., a moderately halophilic bacterium isolated from a saline soil

A novel, Gram-stain-negative, aerobic, rod-shaped, motile and moderately halophilic bacterium, designated strain LCB169T, was isolated from a saline soil sample from Gansu Province, PR China. The cells of LCB169T grew at 10-52u2009°C (optimum 30u2009°C), at pH 6.0-10.0 (optimum pH 8.0) and in the presence of 0-17u200a% (w/v) NaCl (optimum 10-15u200a%). Phylogenetic analysis based on 16S rRNA gene sequences and concatenated 16S rRNA, gyrB and rpoD genes sequences revealed that LCB169T represented a member of the genus Halomonas in the class Gammaproteobacteria. The most closely related species were Halomonas daqingensis DQD2-30T (98.0u200a% 16S rRNA gene sequence similarity), Halomonas kenyensis AIR-2T (97.8u200a%) and Halomonas desiderata FB2T (97.5u200a%). DNA-DNA relatedness values between LCB169T and H. daqingensis CGMCC 1.6443T, H. desiderata DSM 9502T and H. kenyensis DSM 17331T were 33, 35 and 38u200a%, respectively. The polar lipids were identified as diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and three unidentified phospholipids. The major fatty acids were C18u200a:u200a1ω7c, C16u200a:u200a0, C16u200a:u200a1ω7c and C12u200a:u200a0 3-OH. The genomic DNA G+Cu2009content was 66.1u2009mol% and the predominant respiratory quinone was Q-9. On the basis of the results of phenotypic, phylogenetic and chemotaxonomic analyses and DNA-DNA hybridization relatedness values, LCB169T is considered to represent a novel species of the genus Halomonas, for which the name Halomonas saliphila sp. nov. is proposed. The type strain is LCB169T (=CGMCC 1.15818T=KCTC 52618T).