Kine Østnes Hansen

Bacterial biofilms pose a major public health challenge by increasing the antimicrobial tolerance in pathogenic bacteria, thereby limiting the effect of medication-based treatment and promoting the development of antimicrobial resistance. Hence, there is a need to discover new molecules with the ability to prevent biofilm formation. We screened seven synthetic analogues of the breitfussin family of natural products for antimicrobial and antibiofilm activity using a broth microdilution and crystal violet method, respectively. Two compounds inhibited the growth of Gram-positive bacteria in their planktonic state at concentrations of 50 µM, of which one compound (2) demonstrated the ability to inhibit the biofilm formation of Staphylococcus epidermidis at sub-growth-inhibitory, low micromolar concentrations. Compound 2 did not inhibit biofilm growth in Staphylococcus aureus or Listeria monocytogenes, or the ability to eradicate pre-established biofilms. Initial Mode of Action (MoA) studies with compound 2 against S. epidermidis showed a modest impact on the cell surface hydrophobicity and early-stage adhesion to polystyrene. These findings highlight the breitfussin framework as a promising scaffold for the development of new antimicrobial and antibiofilm agents.

Ascidians are a group of marine invertebrates, most of which are sessile and soft-bodied. Their lack of an adaptive immune system makes them rely on innate immune responses to detect and eliminate invading microbes. Antimicrobial peptides (AMPs) play an essential part in this process. In this paper, we present the isolation, structure elucidation, and bioactivities of two new cysteine-rich peptides (CRPs) from the Arctic marine ascidian Synoicum turgens. The sequences and structures of the peptides were determined by Edman degradation sequencing, mass spectrometry, and NMR analysis. This revealed two novel 2 kDa peptides, St-CRP-1 and St-CRP-2, with neutral net charge and C-terminal amidation. St-CRP-1 consisted of 18 amino acids and displayed selective and moderate growth inhibition of two Gram-positive bacterial strains (Bacillus subtilis and Corynebacterium glutamicum) at 24.6 µM, whereas St-CRP-2 consisted of 19 amino acids and inhibited the growth of B. subtilis at 49.2 µM. St-CRP-1 had no effect on two mammalian cell lines or the brine shrimp Artemia salina at the highest concentration tested. Structural analysis of the St-CRPs indicated a Cys1–Cys6, Cys2–Cys4, and Cys3–Cys5 disulfide connectivity, which is also found in alpha-defensins. The results from this study show that Arctic marine ascidians are a rich source of novel bioactive peptides.

Marine diatoms are prolific producers of bioactive metabolites, but Arctic species remain underexplored as sources of antibacterial and antibiofilm agents. Here, seven species were grown in photobioreactors (PBRs) and systematically screened for antibacterial, antibiofilm, and cytotoxic activities. All strains inhibited Gram-positive bacteria, and four reduced Staphylococcus epidermidis biofilm formation. Porosira glacialis emerged as a lead species, combining potent antibiofilm activity with favourable traits for large-scale cultivation, and no detectable cytotoxicity. Bioactivity-guided fractionation of P. glacialis yielded two antibiofilm compounds: methyl 3-hydroxyoctadecanoate, the first time reported in diatoms and newly associated with antibiofilm bioactivity, and pheophorbide a, a chlorophyll degradation product. Both inhibited S. epidermidis biofilm formation without any observed cytotoxicity. Notably, Cylindrotheca closterium exhibited cultivation-dependent antibiofilm activity, underscoring the importance of growth conditions for metabolite production. These findings highlight the potential of Arctic diatoms as a sustainable source of antibiofilm agents and support further exploration of their metabolites for antimicrobial and industrial applications.

The mention of chitin often evokes the Bouligand structure, which is a unique twisted configuration featuring a uniaxial planar organization of fibers. Although a large number of studies focused on Arthropoda, the architecture of chitin in many other invertebrate phyla remains largely unexplored. Herein, we unveil the distinctive architectures of chitin in both Arthropoda and Bryozoa, offering a comparative analysis of the morphological properties of native fibers and chitin nanocrystals sourced from these divergent organisms. In stark contrast to the Bouligand architecture prevalent in Arthropoda, Bryozoa exhibits a unique spiderweb-like arrangement of nanobundle structures, exclusive to this animal group. Bryozoan chitin nanofibers have a diameter smaller than those found among arthropods. After acid hydrolysis, the bryozoan nanocrystals are shorter and have a diameter smaller than those from arthropods. Although the chitin nanocrystals formed the chiral nematic phase, in the current study with the applied methodology, this was not the case with chitin nanocrystals from the studied bryozoan species. The unique chitin nanoarchitecture observed in Bryozoa could serve as an inspiration to produce advanced materials. Their smaller chitin nanocrystals can serve as a potential alternative to those of arthropods.

A marine-derived Pleosporales fungus, Uzbekistanica storfjordensis, was isolated from driftwood and described as a new species. The fungus was cultivated in liquid media and a molecular networking-driven approach was used to identify potential new secondary metabolites. The targeted compounds were isolated using preparative HPLC-MS, and through extensive spectroscopic analysis, eight new ophiobolin-type sesterterpenes, bipolarolides H-O (1-8), were identified. The absolute configurations of the compounds were determined by ECD assessment. Bipolarolide L (5), M (6), and O (8) exhibited inhibitory activity against Streptococcus agalactiae with MIC values of 86, 66, and 64 μM, respectively.

Isolation of bioactive products from the marine environment is considered a very promising approach to identify new compounds that can be used for further drug development. In this work we have isolated three new compounds from the purpuroine family by mass-guided preparative HPLC; purpuroine K-M. These compounds where screened for antibacterial- and antifungal activity, antibiofilm formation and anti-cell proliferation activity. Additionally, apoptosis-, cell cycle-, kinase binding- and docking studies were performed to evaluate the mechanism-of-action. None of the compounds showed activity in antibacterial-, antibiofilm- or antifungal assays. However, one of the isolated compounds, purpuroine K, showed activity against two cell lines, MV-4-11 and MOLM-13, two AML cell lines both carrying the FTL3-ITD mutation. In MV-4-11 cells, purpuroine K was found to increase apoptosis and arrest cells cycle in G1/G0, which is a common feature of FLT3 inhibitors. Interactions between purpuroine K and the FLT3 wild type or FLT3 ITD mutant proteins could however not be elucidated in our kinase binding and docking studies. In conclusion, we have isolated three novel molecules, purpuroine K-M, one of which (purpuroine K) shows a potent activity against FLT3-ITD mutated AML cell lines, however, the molecular target(s) of purpuroine K still need to be further investigated.

As part of our search for bioactive metabolites from understudied marine microorganisms, the new chlorinated metabolite chlovalicin B (1) was isolated from liquid cultures of the marine basidiomycete Digitatispora marina, which was collected and isolated from driftwood found at Vannøya, Norway. The structure of the novel compound was elucidated by spectroscopic methods including 1D and 2D NMR and analysis of HRMS data, revealing that 1 shares its molecular scaffold with a previously isolated compound, chlovalicin. This represents the first compound isolated from the Digitatispora genus, and the first reported fumagillin/ovalicin-like compound isolated from Basidiomycota. Compound 1 was evaluated for antibacterial activities against a panel of five bacteria, its ability to inhibit bacterial biofilm formation, for antifungal activity against Candida albicans, and for cytotoxic activities against malignant and non-malignant human cell lines. Compound 1 displayed weak cytotoxic activity against the human melanoma cell line A2058 (~50% survival at 50 µM). No activity was detected against biofilm formation or C. albicans at 50 µM, or against bacterial growth at 100 µM nor against the production of cytokines by the human acute monocytic leukemia cell line THP-1 at 50 µM.

The Lacinutrix genus was discovered in 2005 and includes 12 Gram-negative bacterial species. To the best of our knowledge, the secondary metabolite production potential of this genus has not been explored before, and examination of Lacinutrix species may reveal novel chemistry. As part of a screening project of Arctic marine bacteria, the Lacinutrix sp. strain M09B143 was cultivated, extracted, fractionated and tested for antibacterial and cytotoxic activities. One fraction had antibacterial activity and was subjected to mass spectrometry analysis, which revealed two compounds with elemental composition that did not match any known compounds in databases. This resulted in the identification and isolation of two novel isobranched lyso-ornithine lipids, whose structures were elucidated by mass spectrometry and NMR spectroscopy. Lyso-ornithine lipids consist of a 3-hydroxy fatty acid linked to the alpha amino group of an ornithine amino acid through an amide bond. The fatty acid chains were determined to be iso-C15:0 (1) and iso-C16:0 (2). Compound 1 was active against the Gram-positive S. agalactiae, while 2 showed cytotoxic activity against A2058 human melanoma cells.

Natural products and their derivatives have served as powerful therapeutics against pathogenic microorganisms and are the mainstay of our currently available treatment options to combat infections. As part of our ongoing search for antimicrobial natural products from marine organisms, one fraction prepared from the Arctic marine bryozoan Securiflustra securifrons was found to be active against the human pathogenic bacterium Streptococcus agalactiae (gr. B). Chemical investigation of the fraction revealed that it contained several variants of the highly modified secondary metabolites known as securamines. The securamines are alkaloids sharing a common isoprene-histamine-tryptamine backbone. In this study, we describe the antimicrobial activities of securamine C, E, and H – J (4, 5, and 1-3) and the attempt to deconvolute the mode of action of 1.

Turgencin A, a potent antimicrobial peptide isolated from the Arctic sea squirt Synoicum turgens, consists of 36 amino acid residues and three disulfide bridges, making it challenging to synthesize. The aim of the present study was to develop a truncated peptide with an antimicrobial drug lead potential based on turgencin A. The experiments consisted of: (1) sequence analysis and prediction of antimicrobial potential of truncated 10-mer sequences; (2) synthesis and antimicrobial screening of a lead peptide devoid of the cysteine residues; (3) optimization of in vitro antimicrobial activity of the lead peptide using an amino acid replacement strategy; and (4) screening the synthesized peptides for cytotoxic activities. In silico analysis of turgencin A using various prediction software indicated an internal, cationic 10-mer sequence to be putatively antimicrobial. The synthesized truncated lead peptide displayed weak antimicrobial activity. However, by following a systematic amino acid replacement strategy, a modified peptide was developed that retained the potency of the original peptide. The optimized peptide StAMP-9 displayed bactericidal activity, with minimal inhibitory concentrations of 7.8 µg/mL against Staphylococcus aureus and 3.9 µg/mL against Escherichia coli, and no cytotoxic effects against mammalian cells. Preliminary experiments indicate the bacterial membranes as immediate and primary targets.