Specific Metabolites in a Phaeodactylum tricornutum Strain Isolated from Western Norwegian Fjord Water.

We have searched for special characteristics in growth, protein expression, fatty acids and volatile organic compounds (VOCs) in a local Phaeodactylum tricornutum Bohlin strain (Bergen Marine Biobank), by comparing it with a common accession strain (CCAP). Differences in growth and expressed proteins were detected between the BMB strain and the CCAP strain, and the BMB strain reached the highest cell densities under the given growth conditions. Fatty acid (FA) analyses showed highest relative eicosapentaenoic acid (EPA) levels in the exponential phase (25.73% and 28.31%), and highest levels of palmitoleic acid (16:1 n-7) in the stationary phase (46.36% and 43.66%) in the BMB and CCAP strain, respectively. The most striking finding of the VOCs analyses was the relatively high levels of ectocarpene, 6-((1E)-butenyl)-1,4-cycloheptadiene, hormosirene, and desmarestene and structurally related compounds, which were exclusively detected in the BMB strain. Many of the VOCs detected in the CCAP and, in particular, in the BMB strain have been reported as antimicrobial agents. We suggest that the array of pheromones and antimicrobial substances could be part of an allelopathic strategy of the BMB strain, dominated by oval cells, thus reflecting the benthic life stage of this morphological form. These findings show the potential for bioactive metabolites in the BMB strain.

Spore swelling and germination as a bioassay for the rapid screening of crude biological extracts for antifungal activity.

Screening for bioactivity is commonly performed in vivo in a bioassay purposefully designed for revealing a defined bioactivity (e.g. fungicide or antibacterial activity). This allows the testing of many crude extracts. In the present work a new method (bioassay) targeting spore swelling and germination to assess antifungal susceptibility is developed and evaluated. Traditionally, antifungal activity has been investigated using disk diffusion assays or micro-well plates. Inhibition is measured as a function of radial growth, inhibition zone or turbidity. The construction of a bioassay composed of germinating fungal spores bears the prospect of being a more rapid method, allowing more extracts to be screened within a shorter time frame. It can also be used to reveal antifungal action at an early state in the prospecting process. Suppression of spore swelling provides early indication of inhibitory potential and the type of swelling curve produced might indicate the mechanism of fungistasis. A strain of Absidia glauca Hagem served as model organism. A Beckman Coulter Multiziser 3 particle analyser was applied for the determination of bioactivity and investigation of the sporangiospores. Inhibition was standardized against two known fungicides (sorbic and benzoic acid). Four biological extract solvents were also tested; where DMSO was found to be the best candidate as extract solvent in the assay. Inhibition was investigated as changes in volumes of the germinating spores using germination as endpoint target. The new bioassay was found to be a simple and rapid method for detection of antifungal activity of extracts.

Marine benthic diatoms contain compounds able to induce leukemia cell death and modulate blood platelet activity.

In spite of the high abundance and species diversity of diatoms, only a few bioactive compounds from them have been described. The present study reveals a high number of mammalian cell death inducing substances in biofilm-associated diatoms sampled from the intertidal zone. Extracts from the genera Melosira, Amphora, Phaeodactylum and Nitzschia were all found to induce leukemia cell death, with either classical apoptotic or autophagic features. Several extracts also contained inhibitors of thrombin-induced blood platelet activation. Some of this activity was caused by a high content of adenosine in the diatoms, ranging from 0.07 to 0.31 microg/mg dry weight. However, most of the bioactivity was adenosine deaminase-resistant. An adenosine deaminase-resistant active fraction from one of the extracts was partially purified and shown to induce apoptosis with a distinct phenotype. The results show that benthic diatoms typically found in the intertidal zone may represent a richer source of interesting bioactive compounds than hitherto recognized.

Proximicin A, B and C, novel aminofuran antibiotic and anticancer compounds isolated from marine strains of the actinomycete Verrucosispora.

A family of three novel aminofuran antibiotics named as proximicins was isolated from the marine Verrucosispora strain MG-37. Proximicin A was detected in parallel in the marine abyssomicin producer "Verrucosispora maris" AB-18-032. The characteristic structural element of proximicins is 4-amino-furan-2-carboxylic acid, a hitherto unknown gamma-amino acid. Proximicins show a weak antibacterial activity but a strong cytostatic effect to various human tumor cell lines.