Culture Medium Optimization and Active Compounds Investigation of an Anti-Quorum Sensing Marine Actinobacterium Nocardiopsis dassonvillei JS106

Quorum sensing inhibitors (QSIs) can block the quorum sensing system and might be useful in therapy of drug-resistant bacterial infections. To explore the anti-quorum sensing actinomycetes from marine habitats, in this study, a marine actinobacterium exhibiting strong anti-quorum sensing activity was isolated from marine sediment and identified as Nocardiopsis dassonvillei JS106. Effects of different culture media on the bioactivity and metabolites production of JS106 were investigated by using single-factor and orthogonal experiments. The results showed that soybean meal and NaCl were two important factors in the culture medium, and could significantly affect both the bioactivity and metabolites production of JS106. By culturing in the optimized medium containing 10 g/L soluble starch, 10 g/L soybean meal, and 15 g/L NaCl at pH 6.5, both metabolites production and anti-quorum sensing activity of JS106 were significantly increased (302 and 241%, respectively) compared to the original condition. The culture liquid of JS106 also showed strong anti-biofilm activity against Staphylococcus aureus and Pseudomonas aeruginosa with the inhibition rate of 77.94 and 50.56% at the concentration of 20 vol %, while it did not inhibit the growth of planktonic cells. Questiomycin A and a new compound 2-hydroxyacetate-3-hydroxyacetamido-phenoxazine (HHP) were isolated and identified from the cultures of JS106. The anti-quorum sensing activities (IC50) of questiomycin A and HHP against violacein production by Chromobacterium violaceum 12472 were 6.82 and 23.59 μg/mL, respectively. The strong anti-quorum sensing activity of N. dassonvillei JS106 indicated that this strain and its active phenoxazine metabolites could have good potential in anti-quorum sensing related applications.