Biological and Chemical Profiling of Marine Derived Bacteria.

Supervisor: Marcel Jaspars (Univ. Aberdeen).
As part of the European Union Research Program, the current investigation reports on work undertaken as part of the MarPipe ITN project, Marine Biodiscovery Centre (MBC), University of Aberdeen. The investigation focused on bacterial types from two contrasting marine environments: Antarctic polar sediment-derived bacteria, and Red Sea warm water, coral and seagrass-derived bacteria. The whole project aimed to follow the complete pipeline in natural products discovery and isolation, but due to time constraints, several subproject positioned at different stages of the pipeline were pursued in parallel. Several methods were attempted for the isolation of bacterial strains. This included the use of several media types, as well as selective techniques. All samples have contributed to the bacterial archive at the MBC. Five strains were successfully isolated from a PYS medium and the crude samples were analysed by LC-MS for manual and software assisted dereplication using The Global Natural Product Social Molecular Networking (GNPS) online platform. This provided an insight into the chemical similarities recognised from MS/MS data between the bacteria, highlighting the similarities of several strains of the genus Pseudoalteromonas. Several strains were identified using 16s rRNA analysis, with the promise that one strain of the psychrophilic Maribacter family, showing the closest homology to Maribacter arcticus, may represent a previously undescribed species. Such a discovery would reconfirm the fact that a severe, polar, and isolated continent such as Antarctica promises a plethora of new biological and biochemical bacterial discoveries. The 5 strains were also selected for full investigation into potential compounds of interest, and from one (SMF6.5) this was successfully completed, leading to the isolation of the known compound N-phenethylacetamide. To the best of our knowledge, this study is the first dedicated chemical profiling within the genus Maribacter. The second stage of the project continued work in the biodiscovery pipeline, based on warm water, Red Sea-derived bacteria samples selected for their antibiotic characteristics. 16 strains were tested against a panel of Gram-positive and Gram-negative strains, and based on the activity against these, two were chosen for investigation. Liquid cultures were grown at medium scale only, which was sufficient for SPE fractionation and dereplication of both strains. The comparative GNPS platform not only identified clusters of chemically similar compounds based on MS/MS observed fragmentation patterns, but allowed for the deduction of the biochemical relationship between them.