Dereplication and targeted isolation of bioactive sulphur compound from bacteria isolated from a hydrothermal field.

Marine micro-organisms in the deep-sea hydrothermal vent systems are considered as potential sources of bioactive natural products. Sixteen bacterial strains were isolated from a deep-sea hydrothermal field and screened for bioactive metabolism studies. After the strains were subjected to bioactive testing at different culture media, chemical dereplication by HPLC coupled to high-resolution mass spectrometer was performed to analyse or determine the main secondary metabolisms in those strains. Strain 06204 was large-scale fermented with relative optimal media, for isolating the desired sulphur compound. Butyrolactone I 3-sulphate was isolated and structurally identified from the extract, guided by dereplication and showed moderate antivirus activities against H3N2 and EV71 viruses. Our study suggests that deep-sea hydrothermal bacteria are good sources of sulphur natural products. Meanwhile, the described approach, mainly bioactive screening, dereplication and targeted isolation, is effective and efficient to discover interesting bioactive compounds in hydrothermal bacteria.

Lutibacter profundi sp. nov., isolated from a deep-sea hydrothermal system on the Arctic Mid-Ocean Ridge and emended description of the genus Lutibacter.

A bacterial strain designated LP1T was isolated from a microbial mat growing on the surface of a black smoker chimney at the Loki's Castle hydrothermal system, which is located on the Arctic Mid-Ocean Ridge. Phylogenetic analyses based on 16S rRNA gene sequences positioned strain LP1T within the family Flavobacteriaceae with Lutibacterholmesii as the closest relative (97.5 % 16S rRNA gene sequence similarity). Strain LP1T was rod-shaped, Gram-reaction-negative and non-motile. It grew in a modified artificial seawater medium supplemented with tryptone and vitamins at pH 5.5-7.5 (optimum pH 6.0-6.5), within a temperature range of 13-34 °C (optimum 23 °C), and under microaerobic conditions. The most abundant fatty acids (>10 %) were iso-C15 : 0 (25.2 %) and iso-C15 : 0 3-OH (14.5 %). The genome of strain LP1T has a DNA G+C content of 29.8 mol%. Based on the results of the polyphasic characterization presented here, strain LP1T is considered to represent a novel species of the genus Lutibacter, for which the name Lutibacter profundi sp. nov. is proposed. The type strain is LP1T (=DSM 100437T =JCM 30585T). An emended description of the genus Lutibacter is also provided to fit the description of strain LP1T.

Parvibaculum hydrocarboniclasticum sp. nov., a mesophilic, alkane-oxidizing alphaproteobacterium isolated from a deep-sea hydrothermal vent on the East Pacific Rise.

An aerobic, alkane-oxidizing bacterium, designated strain EPR92(T), was isolated from hydrothermal fluids that had been collected from a deep-sea vent on the East Pacific Rise (at 9° 50' N 104° 17' W). The cells of the novel strain were Gram-staining-negative rods that measured approximately 1.4 µm in length and 0.4 µm in width. Strain EPR92(T) grew at 20-40 °C (optimum 35 °C), with1.0-5.0% (w/v) NaCl (optimum 2.5%), and at pH 4.0-8.5 (optimum pH 7.5). The generation time under optimal conditions was 63 min. Strain EPR92(T) grew aerobically in artificial seawater minimal medium with n-alkanes as sole carbon and energy sources, and also in artificial seawater medium supplemented with peptone and yeast extract. The predominant fatty acids were C(18:1)ω7c, C(19:0) cyclo ω8c, 11-methyl C(18:1)ω7c and a putative C(12:0) aldehyde. The major polar lipids were phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and four unidentified aminolipids. The major respiratory quinone was Q-10 and the genomic DNA G+C content was 60.7 mol%. Phylogenetic analyses of the 16S rRNA gene showed that strain EPR92(T) belongs in the class Alphaproteobacteria and the recognized species that were most closely related to the novel strain were identified as Parvibaculum indicum P-31(T) (98.7% sequence similarity) and Parvibaculum lavamentivorans DS-1(T) (95.8%). In DNA-DNA hybridizations, the level of DNA-DNA relatedness observed between strain EPR92(T) and P. indicum P-31(T) was 47.7%, indicating that the two strains do not belong to the same species. Based on the phylogenetic, physiological, chemotaxonomic and genetic evidence, strain EPR92(T) represents a novel species within the genus Parvibaculum, for which the name Parvibaculum hydrocarboniclasticum sp. nov. is proposed. The type strain is EPR92(T) ( = DSM 23209 = JCM 16666(T)).