Optimising the DPPH Assay for Cell-Free Marine Microorganism Supernatants

Antioxidants prevent ageing and are usually quantified and screened using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. However, this assay cannot be used for salt-containing samples, such as the cell-free supernatants of marine microorganisms that are aggregated under these conditions. Herein, the DPPH solvent (methanol or ethanol) and its water content were optimized to enable the analysis of salt-containing samples, aggregation was observed for alcohol contents of >70%. The water content of methanol influenced the activities of standard antioxidants but did not significantly affect that of the samples. Based on solution stability considerations, 70% aqueous methanol was chosen as the optimal DPPH solvent. The developed method was successfully applied to the cell-free supernatants of marine bacteria (Pseudoalteromonas rubra and Pseudoalteromonas xiamenensis), revealing their high antioxidant activities. Furthermore, it was concluded that this method would be useful for the screening of marine microorganism–derived antioxidants, which also has numerous potential applications, such as salt-fermented foods.

Biologically active antimicrobial compounds from marine microorganisms (2005-2019)

Introduction: The increase in contagious diseases like nosocomial infections, urinary tract infections, and meningitis has led to the emergence of antimicrobial resistance urgently needs new antimicrobial medication with new modes of action. Some of the antibiotics present in the market have been obtained from terrestrial plants, or extracted semisynthetically from materials which can be fermented. Methods: Marine microorganisms account for approximately 80% of sea biomass and they are essential for the survival and well-being of aquatic habitats owing to their indispensable contribution to biogeochemical cycles and biological processes. In marine ecosystems, microorganisms live as microbial communities in seawater, where symbiotic relationships are formed, and their ecological functions are fulfilled. Results: Marine microorganisms remain the largest, most diverse and most exciting source of structurally and functionally complex antimicrobial agents. They are extremely involved in their structure and functions. Enormous biological wealth lies in marine habitats. These microorganisms are potential sources of novel antimicrobial compounds to combat the most infectious diseases like nosocomial infections, urinary tract infections. Conclusion: This study deals with biologically active antimicrobial compounds taken from marine microorganism source which was reported between the years 2005 and 2019. This review highlights their chemical groups, their bioactivities and sources. Marine microorganism exploitation techniques have also been reported by the authors.

Expression, purification, crystallization and X-ray crystallographic analysis of the periplasmic binding protein VatD fromVibrio vulnificusM2799

Vibrio vulnificusis a halophilic marine microorganism which causes gastroenteritis and primary septicaemia in humans. An important factor that determines the survival ofV. vulnificusin the human body is its ability to acquire iron. VatD is a periplasmic siderophore-binding protein fromV. vulnificusM2799. The current study reports the expression, purification and crystallization of VatD. Crystals of both apo VatD and a VatD–desferrioxamine B–Fe3+(VatD–FOB) complex were obtained. The crystal of apo VatD belonged to space groupP6422, while the crystal of the VatD–FOB complex belonged to space groupP21. The difference in the two crystal forms could be caused by the binding of FOB to VatD.