Production, isolation and bioactivity studies of secondary metabolites from arctic marine Microbacterium sp.

Abstract

Bacteria have colonized countless habitats on earth, including extreme environments such as the Arctic Ocean. In 2020, a research cruise arranged by Marbio, a bioprospecting research group at UiT, went out to the Barents Sea to collect marine fungi, invertebrate, and bacteria samples. Especially Actinobacteria were of interest, as they have shown to be prolific producers of secondary metabolites. Secondary metabolites are non-essential compounds produced by many organisms and used for defence against pathogens or predators among other purposes. This is especially of interest for the pharmaceutical use of secondary metabolites, then called natural products. As anti-microbial resistance remains a growing global issue, finding new alternatives for treating infectious diseases has become a focal point in research, with bioprospecting becoming more important.

In this thesis, the aim was to re-isolate two previously identified target compounds, with a third one nominated during this thesis, from two Actinobacteria species, Microbacterium sp., in increased culture volumes to increase compound yield for bioactivity testing and elucidation of structure and mode of action. For this, the bacteria were cultivated, and the crude bacterial extract was produced using solid phase extraction. The target compounds were purified using preparative-HPLC and identified via a mass-spectrometry. Bioactivity and mode of action were investigated using viability assay and anti-inflammatory assays.

Target compound isolation was done from both strains. The yields of the increased cultivations were minimal, and did not differ from the prior cultivations of the same strains. It was concluded that the two strains both produce one of the target compounds. The viability assay showed no toxic effect. The anti-inflammatory assay showed no inhibition of TNF-α. There was a trend towards TNF-α promotion that needs further investigation, as the assay is not designed for detecting immunostimulatory effects. It is hypothesised that two of the target compounds are antagonists for the receptor E-selectin, which needs further research.