PJS, a novel isocoumarin with hexahydropyrimidine ring from Bacillus subtilis PJS

A Gram-staining-negative, non-spore-forming, short, straight rod, non-motile, and obligate anaerobic bacterial strain, AF73-05CM02^T, was isolated from a fecal sample of a 30 years old healthy male living in Shenzhen, China. Colonies were approximately 0.2 mm in diameter, beige, and circular after 4 days of incubation on PYG agar under anaerobic conditions at 37°C. Strain AF73-05CM02^T grew in a temperature range between 30 and 42°C and a pH range from 6.0 to 8.5, with optimum growth at 37–42°C and pH 7.0. 16S rRNA gene sequence analysis demonstrated that strain AF73-05CM02^T belongs to the genus Christensenella and showed the highest level of sequence similarity (98.68%) with Christensenella minuta DSM 22607^T. The predominant fatty acids of strain AF73-05CM02^T were C_10:0 (7.5%), iso-C_11:0 (5.6%), C_12:0 (7.2%), C_14:0 (46.6%), iso-C_15:0 (7.4%), C_16:0 (9.7%), and C_18:1 ω9c (6.9%). Acetic acid, formic acid, butyric acid, and lactic acid were the end products of glucose fermentation. The strain was negative for catalase, indole production, and hydrolysis of gelatin. Genomic relatedness analyses based on average nucleotide identity (ANI) indicated that strain AF73-05CM02^T significantly differed from other species of the genus Christensenella, showing ANI values less than 82.89% with the phylogenetically closest species. The G + C content of the genomic DNA was 52.07 mol% from the genome sequence, which differs from that of Christensenella minuta. Several physiological, biochemical, and genotypic properties differentiated the novel bacterial strain from the related species, indicating that the strain represents a new species of the genus Christensenella for which the name Christensenella intestinihominis sp. nov. is proposed, with strain AF73-05CM02^T ( = CGMCC 1.5207^T = DSM 103477^T ) being the type strain. The following study explored the cholesterol-lowering function of strains AF73-05CM02^T and Christensenella minuta DSM 22067^T and revealed that the two strains exhibit the capacity for removing cholesterol with efficiency rates of 36.6 and 54.3% and produce exopolysaccharide of 234 and 271 mg/L, respectively.

Journal of Antibiotics, official journal of the Japan Antibiotics Research Association, is a print and online publication that focuses on research on antibiotics and related types of medicinal substances

A novel endophytic actinobacterium, designated strain 8BXZ-J1T, was isolated from surface-sterilized branches of Thespesia populnea collected from Beilun Estuary Mangrove Forest National Nature Reserve in Guangxi, China, and examined by a polyphasic approach to determine its taxonomic position. Cells of the isolate were Gram-stain-positive, aerobic, non-spore-forming, non-motile and short rod-shaped. Phylogenetic analysis based on 16S rRNA gene sequences suggested that strain 8BXZ-J1T belonged to the genus Marmoricola , sharing highest similarity with Marmoricola solisilvae DSM 27140T (96.9 %). The isolate grew at 10–35 °C (optimum, 28–30 °C), at pH 6.0–8.0 (optimum, pH 7.0) and in the presence of 0–10 % (w/v) NaCl (optimum, 0–5.0 %). The organism contained ll-2,6-diaminopimelic acid as the diagnostic diamino acid of the peptidoglycan, MK-8(H4) as the major menaquinone, and a polar lipid profile including diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, phosphatidylinositol and two unknown lipids. The major fatty acids of strain 8BXZ-J1T were C18 : 0 10-methyl, iso-C16 : 0 and C16 : 0. The G+C content of the genomic DNA was 68.7 mol%. These data demonstrate that strain 8BXZ-J1T is representative of a novel species of the genus Marmoricola , for which the name Marmoricola endophyticus sp. nov. is proposed. The type strain is 8BXZ-J1T (=KCTC 39789T=CGMCC 1.16067T).

To combat escalating levels of antibiotic resistance, novel strategies are developed to address the everlasting demand for new antibiotics. This study aimed at investigating amicoumacin antibiotics from the desert-derived Bacillus subtilis PJS by using the modern MS/MS-based molecular networking approach. Two new amicoumacins, namely hetiamacin E (1) and hetiamacin F (2), were finally isolated. The planar structures were determined by analysis of extensive NMR spectroscopic and HR–ESI–MS data, and the absolute configurations were concluded by analysis of the CD spectrum. Hetiamacin E (1) showed strong antibacterial activities against methicillin-sensitive and resistant Staphylococcus epidermidis at 2–4 µg/mL, and methicillin-sensitive and resistant Staphylococcus aureus at 8–16 µg/mL. Hetiamacin F (2) exhibited moderate antibacterial activities against Staphylococcus sp. at 32 µg/mL. Both compounds were inhibitors of protein biosynthesis demonstrated by a double fluorescent protein reporter system.

Taklamakan desert is known as the largest dunefield in China and as the second largest shifting sand desert in the world. Although with long history and glorious culture, the Taklamakan desert remains largely unexplored and numerous microorganisms have not been harvested in culture or taxonomically identified yet. The main objective of this study is to explore the diversity, novelty, and pharmacological potential of the cultivable actinomycetes from soil samples at various sites along the Alar-Hotan desert highway in the Taklamakan desert. A total of 590 actinobacterial strains were recovered by the culture-dependent approach. Phylogenetic analysis based on 16S ribosomal RNA (rRNA) gene sequences unveiled a significant level of actinobacterial diversity with 55 genera distributed in 27 families of 12 orders. Thirty-six strains showed relatively low 16S rRNA similarities (<98.65%) with validly described species, among which four strains had already been characterized as novel taxa by our previous research. One hundred and forty-six actinobacterial isolates were selected as representatives to evaluate the antibacterial activities and mechanism of action by the paper-disk diffusion method and a double fluorescent protein reporter “pDualrep2” system, respectively. A total of 61 isolates exhibited antagonistic activity against the tested “ESKAPE” pathogens, among which seven strains could produce bioactive metabolites either to be able to block translation machinery or to induce SOS-response in the pDualrep2 system. Notably,Saccharothrixsp. 16Sb2-4, harboring a promising antibacterial potential with the mechanism of interfering with protein translation, was analyzed in detail to gain deeper insights into its bioactive metabolites. Through ultra-performance liquid chromatography (UPLC)-quadrupole time-of-flight (QToF)-MS/MS based molecular networking analysis and databases identification, four families of compounds (1–16) were putatively identified. Subsequent bioassay-guided separation resulted in purification of four 16-membered macrolide antibiotics, aldgamycin H (8), aldgamycin K (9), aldgamycin G (10), and swalpamycin B (11), and their structures were elucidated by HR-electrospray ionization source (ESI)-MS and NMR spectroscopy. All compounds8–11displayed antibacterial activities by inhibiting protein synthesis in the pDualrep2 system. In conclusion, this work demonstrates that Taklamakan desert is a potentially unique reservoir of versatile actinobacteria, which can be a promising source for discovery of novel species and diverse bioactive compounds.