The article highlights the available data on Antarctic bacteria, their biosynthetic potential, and the successful NP discoveries while addressing the challenges in NP research and advocating for systematic, collaborative research in Antarctica.

In polar ecosystems, primary producers have to cope with a very harsh climate that limits the time available for growth and biomass production. In this study, diurnal measurement of photosynthetic processes in biological soil crust and a lichen were carried out in Petuniabukta, Spitsbergen. For field measurements, a method of induced fluorescence of chlorophyll was used. Measurements of photosynthetic activity were taken as repetitive measurements of effective quantum yield of photosystem II (ΦPSII). The short-term field measurements were carried out for 10 days in summer 2014. ΦPSII was recorded each 5 minutes as well as microclimatic data (air temperature, air humidi-ty, photosynthetically active radiation - PAR). The microclimatic parameters were recorded by a datalogger. In general, physiological activity of both biological soil crust and a lichen showed daily courses. Tested lichen was Cladonia rangiferina and the most dominant species in biological soil crust was Nostoc sp. Typically, most of ΦPSII values ranged 0.6 – 0.7 in both model organisms. The results have shown that photosynthetic activity was strongly correlated with all observed abiotic factors in both study objects. Particularly important was the relation found between PAR and ΦPSII in biological soil crust. When the biological soil crust was exposed to high PAR doses of irradiation (about 2300 µmol m-2 s-1) photoinhibition of primary processes of photosynthesis was observed as ΦPSII decrease, while photosynthetic activity of lichen remained at same level. Furthermore, it has been demonstrated increasing that in situ photosynthetic activity increased in both biological soil crust and lichen with a decrease in temperature.

Although information about the occurrence and distribution of retinoids in the environment is scarce, cyanobacterial water blooms have been identified as a significant source of these small molecules. Despite the confirmed presence of retinoids in the freshwater blooms dominated by cyanobacteria and their described teratogenic effects, reliable identification of retinoid producers and the mechanism of their biosynthesis is missing. In this study, the cultures of several taxonomically diverse species of axenic cyanobacteria were confirmed as significant producers of retinoid-like compounds. The consequent bioinformatic analysis suggested that the enzymatic background required for the biosynthesis of all-trans retinoic acid from retinal is not present across phylum Cyanobacteria. However, we demonstrated that retinal conversion into other retinoids can be mediated non-enzymatically by free radical oxidation, which leads to the production of retinoids widely detected in cyanobacteria and environmental water blooms, such as all-trans retinoic acid or all-trans 5,6epoxy retinoic acid. Importantly, the production of these metabolites by cyanobacteria in association with the mass development of water blooms can lead to adverse impacts in aquatic ecosystems regarding the described teratogenicity of retinoids. Moreover, our finding that retinal can be non-enzymatically converted into more bioactive retinoids, also in water, and out of the cells, increases the environmental significance of this process.

Secondary metabolites are compounds not essential for an organism’s development, but provide significant ecological and physiological benefits. These compounds have applications in medicine, biotechnology, and agriculture. Their production is encoded in biosynthetic gene clusters (BGCs), groups of genes collectively directing their biosynthesis. The advent of metagenomics has allowed researchers to study BGCs directly from environmental samples, identifying numerous previously unknown BGCs encoding unprecedented chemistry. Here, we present the BGC Atlas ( https://bgc-atlas.cs.uni-tuebingen.de ), a web resource that facilitates the exploration and analysis of BGC diversity in metagenomes. The BGC Atlas identifies and clusters BGCs from publicly available datasets, offering a centralized database and a web interface for metadata-aware exploration of BGCs and gene cluster families (GCFs). We analyzed over 35,000 datasets from MGnify, identifying nearly 1.8 million BGCs, which were clustered into GCFs. The analysis showed that ribosomally synthesized and post-translationally modified peptides (RiPPs) are the most abundant compound class, with most GCFs exhibiting high environmental specificity. We believe that our tool will enable researchers to easily explore and analyze the BGC diversity in environmental samples, significantly enhancing our understanding of bacterial secondary metabolites, and promote the identification of ecological and evolutionary factors shaping the biosynthetic potential of microbial communities.

Surface and treated wastewaters are contaminated with highly complex mixtures of micropollutants, which may cause adverse effects on aquatic biota or humans, often mediated by endocrine disruption. However, there is very limited knowledge regarding some important modes of action, such as interference with thyroid hormone (TH) regulation and the compounds driving these effects. The effects of environmental samples observed in bioassays addressing various endpoints in the endocrine, namely thyroid hormone pathways, remain largely unexplained with known active chemicals. Transthyretin (TTR) is a serum transport protein distributing thyroid hormones to target tissues in vertebrates; its binding inhibition by xenobiotics may lead to adverse effects such as impaired (neuro)development. In this study, we describe a novel approach for the identification of compounds with the potential to bind to TTR, based on the specific separation of these compounds in a pull-down assay followed by non-target analysis (NTA). The pull-down assay using purified TTR protein was established and optimized with known TTR ligands. The method was applied to separate and identify compounds responsible for TH displacing activity in highly complex wastewater and surface water samples. The samples after the pull-down assay elicited TH displacing activity and the specific separation of TTR ligands provided a substantial reduction of chromatographic features from the original complex water extract. The applied non-target screening workflow resulted in the identification of 34 structures. Thirteen identified compounds with available analytical standards were quantified in the original water extracts and their TH-displacement potency was confirmed. Twelve compounds were discovered as TTR binders for the first time and linear alkylbenzene sulfonates (LAS) were highlighted as contaminants of concern regarding the TH-displacement activity. Pull-down assay combined with NTA proved to be a well-functioning approach for the identification of bioactive compounds in complex environmental mixtures with great application potential across various biological target endpoints and environmental compartments.