Biological activities and metabolomic profiles of extracts from the marine sediment bacterium Nocardiopsis alba DP1B cultivated in different media.

The soil bacterium DP1B was isolated from a marine sediment collected off the coast of Randayan Island, Kalimantan Barat, Indonesia and identified based on 16S rDNA as Nocardiopsis alba. The bacterium was cultivated in seven different media (A1, ISP1, ISP2, ISP4, PDB, PC-1, and SCB) with three different solvents [distilled water, 5 % NaCl solution, artificial seawater (ASW)] combinations, shaken at 200 rpm, 30 °C, for 7 days. The culture broths were extracted with ethyl acetate and each extract was tested for its antimicrobial activity and brine shrimp lethality, and the chemical diversity was assessed using thin-layer chromatography (TLC), gas chromatography (GC), and liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS). The result showed that almost all extracts showed antibacterial but not antifungal activity, whereas their brine shrimp toxicity levels vary from high to low. The best medium/solvent combinations for antibacterial activity and toxicity were PC-1 (in either distilled water, 5% NaCl solution, or ASW) and SCB in ASW. Different chemical diversity profiles were observed on TLC, GC-MS, and LC-MS/MS. Extracts from the PC-1 cultures seem to contain a significant number of cyclic dipeptides, whereas those from the SCB cultures contain sesquiterpenes, indicating that media and solvent compositions can affect the secondary metabolite profiles of DP1B. In addition, untargeted metabolomic analyses using LC-MS/MS showed many molecular ions that did not match with those in the Global Natural Products Social Molecular Networking (GNPS) database, suggesting that DP1B has great potential as a source of new natural products.

Diversity of Myxobacteria Isolated from Indonesian Mangroves and Their Potential for New Antimicrobial Sources.

Mangroves are unique intertidal ecosystems that provide ecological niches to different microbes, which play various roles in nutrient recycling and diverse environmental activities. The association between myxobacteria and mangroves are hitherto poorly understood. The aim of our study was to evaluate the myxobacterial community composition as well as isolate myxobacteria and to characterize the antimicrobial activity of myxobacteria isolates from Indonesian mangroves. Twenty-five cultivable myxobacteria were affiliated in six genera: Myxococcus, Corallococcus, Archangium, Chondromyces, Racemicystis and Nannocystis of the order Myxococcales based on partial 16S rRNA gene sequences. Thirteen crude extracts showed moderate activities against at least one of human pathogenic microorganisms. The crude extract of Racemicystis sp. strain 503MSO indicated a novel compound, which has not been reported in the database yet and the identification of this compound needs further study. The myxobacterial communities of three different sampling sites were analyzed using primers adapted for the myxobacteria group identification. The results showed that myxobacterial communities are more diverse than assumed. Therefore, our study has highlighted the importance of the mangrove habitat as promising harbor of myxobacteria as well as novel antimicrobial compounds with activity against pathogenic microorganisms.

Four new members of the family Cytophagaceae: Chryseosolibacter histidini gen. nov., sp. nov., Chryseosolibacter indicus gen. nov., sp. nov., Dawidia cretensis, gen. nov., sp. nov., and Dawidia soli, gen. nov., sp. nov. isolated from diverse habitat.

Four novel strains were isolated: PWU4T and PWU20T were both from soil in Germany, PWU5T was isolated from soil in India and PWU37T was obtained from sheep faeces collected on the Island of Crete. Cells of each were observed to be Gram-negative, strictly aerobic, rod shaped, and to grow optimally between 28 and 34 °C, between pH 7.0 and 8.0 and without the addition of NaCl. The strains were found to be catalase and oxidase-negative and able to grow on most mono- and disaccharides, a few polysaccharides and organic acids. Their predominant menaquinone was identified as MK-7. Their major fatty acids were identified as C16:1 ω7c (PWU4T and PWU20T) and C16:1 ω5c (PWU5T and PWU37T). The DNA G + C contents of strains PWU4T, PWU20T, PWU5T and PWU37T were determined to be 50.2 mol%, 51.6 mol %, 39.8 mol% and 53.8 mol%, respectively. The 16S rRNA gene sequence analysis revealed that the close relatives Ohtaekwangia koreensis 3B-2T and Ohtaekwangia kribbensis 10AOT share less than 93.8% sequence similarity. The strains were classified in two groups, where PWU4T and PWU20T share 93.0% sequence similarity, and PWU5T and PWU37T share 97.5% sequence similarity. However, the members of each group were concluded to represent different species based on the low average nucleotide identity (ANI) of their genomes, 69.7% and 83.8%, respectively. We propose that the four strains represent four novel species of two new genera in the family Cytophagaceae. The type species of the novel genus Chryseosolibacter is Chryseosolibacter histidini gen. nov., sp. nov. with the type strain PWU4T (= DSM 111594T = NCCB 100798T), whilst strain PWU20T (= DSM 111597T = NCCB 100800T) is the type strain of a second species, Chryseosolibacter indicus sp. nov. The type species of the novel genus Dawidia is Dawidia cretensis gen. nov., sp. nov. with the type strain PWU5T (= DSM 111596T = NCCB 100799T), whilst strain PWU37T (= DSM 111595T = NCCB 100801T) is the type stain of a second species, Dawidia soli sp. nov.