Publications of Emmanuelle Javaux
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See detailAdaptations to extreme conditions: the strategy of the Antarctic cyanobacterium ULC007
Lara, Yannick ULiege; Durieu, Benoit ULiege; Javaux, Emmanuelle ULiege et al

Conference (2018, December 18)

In Polar regions, freshwater ecosystems range from cryoecosystems and ice shelf meltwater ponds to perennially ice-covered lakes where conspicuous benthic microbial mat communities constitute most of the ... [more ▼]

In Polar regions, freshwater ecosystems range from cryoecosystems and ice shelf meltwater ponds to perennially ice-covered lakes where conspicuous benthic microbial mat communities constitute most of the biomass. In these mats, cyanobacteria form the matrix in which other microorganisms can live, and where they are the key primary producers and main drivers of the carbon and food webs. To provide a better understanding of the survival strategies of Polar mat-forming cyanobacteria, we investigated the genome of a strain of the widely distributed Antarctic cyanobacterium, Phormidium priestleyi ULC007. We used high-throughput sequencing technologies to investigate its geographic distribution and genome evolution. More precisely, we investigated the abundance of genes involved in cold adaptation and circadian oscillation. In cold habitats, low temperatures lead to the success of particular organisms featuring adaptations to molecular and cellular disturbances such as higher rigidity of membranes, reduction of enzyme-catalyzed reactions, and reduction of solute transport. Our main results underline the importance of functional categories of genes involved in the production of key molecules for the survival of P. priestleyi in cold conditions (e.g. synthesis of exopolysaccharides, chaperone proteins, fatty acids and phospholipids). [less ▲]

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See detailBCCM/ULC: a collection of cyanobacteria linking Poles to Space
Wilmotte, Annick ULiege; Beets, Kim ULiege; Santoro, Mariano ULiege et al

Conference (2018, December 18)

The BCCM/ULC public collection funded by the Belgian Science Policy Office (BELSPO) aims to gather a representative portion of the cyanobacterial diversity with a focus on Polar biotopes (e.g. limnetic ... [more ▼]

The BCCM/ULC public collection funded by the Belgian Science Policy Office (BELSPO) aims to gather a representative portion of the cyanobacterial diversity with a focus on Polar biotopes (e.g. limnetic microbial mats, soil crusts, cryoconites, endolithes). It represents an exclusive Biological Resource Centre (BRC) where characterized polar cyanobacterial strains are available for researchers to study the taxonomy, biogeography, evolution, synthesis of secondary metabolites, adaptation to harsh environmental conditions, and genomic make-up. It currently holds 190 strains, including over 120 of Polar origin (online catalogue: http://bccm.belspo.be/catalogues/ulc-catalogue-search). Living cultures are regularly transferred, and the majority are also cryopreserved (as back-up), in order to assure their preservation and the rapid delivery of strains to clients for fundamental and applied research in both academia and industry. Genomic DNA is also available on request. The collection has obtained the ISO 9001:2015 certification for deposit and distribution of strains, as part of the multi-site certification for the Belgian Coordinated Collections of Microorganisms (BCCM) consortium. A polyphasic approach based on morphological and molecular identifications (based on SSU rRNA sequences) show that the strains belong to the Synechococcales, Oscillatoriales, Chroococcidiopsidales, Pleurocapsales, and Nostocales orders. This large diversity renders the BCCM/ULC collection particularly interesting for taxonomic, biogeographic and phylogenomic studies. Furthermore, the sequencing of the genomes of several strains has started. The BRC also aims to become a source for researchers to study further applications of cyanobacteria in astrobiology as shown by investigations of the resistance to desiccation and radiation of strains of Chroococcidiopsis sp. dominating rock-dwelling communities in extreme dry environments [1]. In paleontology, cyanobacteria represent model organisms thanks to their fundamental role in the oxygenation of the atmosphere and oceans during the Great Oxidation Event. Lastly, the mat-forming cyanobacterial strains may represent “critical organisms” in the investigation of the factors that determine the boundaries of microbial survival and growth on Earth and in the space environment, by virtue of the fact that they are components of microbial mat model systems which are more and more used to elucidate Earth’s past and the detection of life’s biosignatures. [less ▲]

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See detailEarly eukaryote Paleobiology and Evolution
Javaux, Emmanuelle ULiege

Conference (2018, November 21)

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See detailThe earliest evidence for modern-style plate tectonics recorded by HP–LT metamorphism in the Paleoproterozoic of the Democratic Republic of the Congo
François, Camille ULiege; Debaille, Vincianne ULiege; Paquette, Jean-Louis et al

in Scientific Reports (2018), 8(15452),

Knowing which geodynamic regimes characterised the early Earth is a fundamental question. This implies to determine when and how modern plate tectonics began. Today, the tectonic regime is dominated by ... [more ▼]

Knowing which geodynamic regimes characterised the early Earth is a fundamental question. This implies to determine when and how modern plate tectonics began. Today, the tectonic regime is dominated by mobile-lid tectonics including deep and cold subduction. However, in the early Earth (4.5 to 2 Ga) stagnant-lid tectonics may also have occurred. The study of high pressure–low temperature (HP–LT) metamorphic rocks is important, because these rocks are only produced in present-day subduction settings. Here, we characterize the oldest known HP–LT eclogite worldwide (2089 ± 13 Ma; 17–23 kbar / 500-550°C), discovered in the Democratic Republic of the Congo. We provide evidence that the mafic protolith of the eclogite formed at 2216 ± 26 Ma in a rift-type basin, and was then subducted to mantle depths (> 55 km) before being exhumed during a complete Wilson cycle lasting ca. 130 Ma. Our results indicate the operation of modern mobile-lid plate tectonics at 2.2–2.1 Ga. [less ▲]

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See detailBack to the past: a glance at microscopic marine diversity 1 billion year ago
Loron, Corentin ULiege; Javaux, Emmanuelle ULiege

Conference (2018, October 11)

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See detailThe BCCM/ULC collection of cyanobacteria in the spotlight at ULiège
Santoro, Mariano ULiege; Beets, Kim ULiege; Simons, Véronique et al

Poster (2018, October 11)

The ULC public collection of cyanobacteria belongs since 2011 to the consortium of Belgian Co-Ordinated Collections of Microorganisms (BCCM). It aims to conserve ‘ex situ’ a representative portion of the ... [more ▼]

The ULC public collection of cyanobacteria belongs since 2011 to the consortium of Belgian Co-Ordinated Collections of Microorganisms (BCCM). It aims to conserve ‘ex situ’ a representative portion of the biodiversity of cyanobacterial diversity of different origins, with a focus on Antarctic and Artic cyanobacteria isolated from terrestrial and aquatic ecosystems. BCCM/ULC currently holds 174 cyanobacterial strains that are available for researchers who study taxonomy, evolution, biogeography and the adaptation to harsh environmental conditions. The strains are identified by morphology and molecular characterization (based on rRNA sequences) and belong to the Synechococcales, Oscillatoriales, Pleurocapsales, Chroococcidiopsidales and Nostocales orders. This large taxonomic distribution renders it a suitable reference point for phylogenomic and genomic make-up studies. Regular transfer of living cultures ensures the conservation of strains, whose majority are also cryopreserved in order to limit the genetic drift. BCCM/ULC obtained an ISO 9001:2015 certification for public and safe deposits, and for distribution of living strains and genomic DNA. The BCCM policy continuously aims to guarantee a safe fit-for-use microbiological material and data compliant with the rules on access and utilization of the Nagoya Protocol. In addition, BCCM/ULC provides, to clients from academia & industry, a service of morphological identification and molecular characterization, along with other scientific services as tailor-made trainings and collaborations. The public collection is progressively enriched by public deposits from other geographical areas and by incorporating the most interesting strains from the research collection of the host laboratory. The latter is also involved in the valorisation of the collection and collaborations, aiming to study the molecular mechanisms of adaptation to cold stress in polar strains, their production of potential bioactive compounds, to decipher and analyze their genomes and to determine the usefulness of their pigments as ‘traces of life’ in astrobiology. [less ▲]

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See detailLes Cyanobactéries, microscopiques mais fondamentales !
Javaux, Emmanuelle ULiege; Jacques, Philippe ULiege; Wilmotte, Annick ULiege

Scientific conference (2018, September 26)

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See detailArchean geodynamics and the onset of plate tectonics
Debaille, Vinciane; François, Camille ULiege; Javaux, Emmanuelle ULiege et al

Conference (2018, September)

Since the Archean (between 4 to 2.5 Gyr ago) was much hotter than the present time because of higher rates of internal heat production, it is traditionally accepted that the mantle was convecting faster ... [more ▼]

Since the Archean (between 4 to 2.5 Gyr ago) was much hotter than the present time because of higher rates of internal heat production, it is traditionally accepted that the mantle was convecting faster, resulting in faster mixing time and also plates at the surface of the Earth moving faster. Short-lived isotope systems are particularly adapted to understand the geological processes that occurred during the Archean because their production stopped at some point in the past and only mixing can subsequently modify them. As such, the system 146Sm-142Nd where 146Sm was extinct ~0.5 Gyr after the formation of the solar system is particularly useful to investigate the Earth’s early geodynamics. By using this system, we found a resolvable positive anomaly of µ142Nd = + 7 ± 3 ppm in a 2.7 Gyr old tholeiitic lava flow from the Abitibi Greenstone Belt indicating that early mantle heterogeneities formed between 4 and 4.5 Gyr persisted ~1.8 Gyr after Earth’s formation [1]. This result contradicts the expected rapid early (~0.1 Gyr) [2, 3], as well as the slower recent (~1 Gyr) mixing rates in the convecting mantle [3-5]. We developed a numerical modelling [1, 6] which suggests that inefficient convective mixing can occur even in a highly convective mantle in absence of plate tectonics, i.e. in a stagnant-lid regime. Our model allows only sporadic and short subduction episodes throughout the Hadean and Archean in order to explain the long-term preservation of chemical anomalies in a highly convective mantle. Modern subduction is characterized by (U)HP-LT metamorphism resulting eclogite-facies rocks. Eclogites are absent from the Archean record, hence corroborating the absence of modern-style subduction zones. On the other hand, we will also present the oldest evidence of HP-LT eclogite at 2.1 Gyr from the Congo craton, which is a clear indicator that the 2.7-2.1 Gyr period was a turning point for the onset of modern plate tectonics on Earth [7]. References: [1] Debaille, et al. (2013), Earth Planet. Sci. Lett., 373, 83-92. [2] van Keken and Zhong (1999), Earth Planet. Sci. Lett., 171 533-547. [3] Coltice and Schmalzl (2006), Geophys. Res. Lett., 33, L23304. [4] Kellogg and Turcotte (1990), J. Geoph. Res., 95, 421-432. [5] Allègre, et al. (1995), Geophys. Res. Lett., 22, 2325-2328. [6] O'Neill, et al. (2013), American Journal of Science, 313, 912-932. [7] François, et al. in review. [less ▲]

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See detail1.1 billion years old porphyrins and their isotopic composition establish a marine ecosystem dominated by bacterial primary producers
Gueneli, Nur; McKenna, AC; Ohkouchi et al

in Proceedings of the National Academy of Sciences of the United States of America (2018)

The average cell size of marine phytoplankton is critical for the flow of energy and nutrients from the base of the food web to higher trophic levels. Thus, the evolutionary succession of primary ... [more ▼]

The average cell size of marine phytoplankton is critical for the flow of energy and nutrients from the base of the food web to higher trophic levels. Thus, the evolutionary succession of primary producers through Earth’s history is important for our understanding of the radiation of modern protists ∼800 million years ago and the emergence of eumetazoan animals ∼200 million years later. Currently, it is difficult to establish connections between primary production and the proliferation of large and complex organisms because the mid-Proterozoic (∼1,800–800 million years ago) rock record is nearly devoid of recognizable phytoplankton fossils. We report the discovery of intact porphyrins, the molecular fossils of chlorophylls, from 1,100-million-year-old marine black shales of the Taoudeni Basin (Mauritania), 600 million years older than previous findings. The porphyrin nitrogen isotopes (δ15Npor = 5.6–10.2‰) are heavier than in younger sedimentary sequences, and the isotopic offset between sedimentary bulk nitrogen and porphyrins (εpor = −5.1 to −0.5‰) points to cyanobacteria as dominant primary producers. Based on fossil carotenoids, anoxygenic green (Chlorobiacea) and purple sulfur bacteria (Chromatiaceae) also contributed to photosynthate. The low εpor values, in combination with a lack of diagnostic eukaryotic steranes in the time interval of 1,600–1,000 million years ago, demonstrate that algae played an insignificant role in mid-Proterozoic oceans. The paucity of algae and the small cell size of bacterial phytoplankton may have curtailed the flow of energy to higher trophic levels, potentially contributing to a diminished evolutionary pace toward complex eukaryotic ecosystems and large and active organisms. [less ▲]

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See detailPaleoproterozoic HP-LT eclogites from the DRCongo: Implications for the onset of plate tectonics on Earth
François, Camille ULiege; Debaille, Vinciane; Paquette, Jean-Louis et al

Poster (2018, June)

Knowing the plate tectonic regime of the early Earth is a fundamental but ongoing question and its resolution implies to know when and how plate tectonics and subduction began on Earth. Today, the ... [more ▼]

Knowing the plate tectonic regime of the early Earth is a fundamental but ongoing question and its resolution implies to know when and how plate tectonics and subduction began on Earth. Today, the tectonic regime is ruled by mobile-lid tectonics including subduction. However, in the early Earth stagnant-lid tectonics (or sagduction) could also occur. The possible range for the onset of mobile-lid plate tectonic spans from the early Archean to mid-Proterozoic, even though the Neoarchean-Paleoproterozoic boundary seems to be a crucial period and a time of major change in tectonic style regime on Earth. The study of High Pressure-Low Temperature (HP-LT) metamorphic rocks is powerful because today, these rocks are only produced in subduction settings. Here, we characterize the oldest HP-LT eclogite worldwide (2089 ± 13 Ma; 20-25 kbar / 550-600°C) discovered in the Kasai Block (DRCongo) attesting subduction process. We also identify the gabbroic protolith of this rock formed at 2216 ± 26 Ma in a rift-type basin, then was buried at high depth (> 65 km) in a subduction zone and exhumed during a Wilson cycle of ca. 130 Ma, testifying a modern-style plate tectonics at 2.2-2.1 Ga. [less ▲]

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See detailRaman microspectroscopy, bitumen reflectance and illite crystallinity scale: comparison of different geothermometry methods on fossiliferous Proterozoic sedimentary basins (DR Congo, Mauritania and Australia)
Kabamba Baludikay, Blaise ULiege; François, Camille ULiege; Sforna, Marie-Catherine ULiege et al

in International Journal of Coal Geology (2018)

Sedimentary rocks containing microfossils are crucial archives to reconstitute early life evolution on Earth. However, the preservation of microfossils within rocks depends on several physico-chemical ... [more ▼]

Sedimentary rocks containing microfossils are crucial archives to reconstitute early life evolution on Earth. However, the preservation of microfossils within rocks depends on several physico-chemical factors. Among these factors, the thermal evolution of the host rocks can be decisive. Here, we investigated carbonaceous shale samples containing exquisitely preserved organic-walled microfossils assemblages from three Proterozoic shallow marine sedimentary sequences: the Mbuji-Mayi Supergroup (Democratic Republic of Congo, Congo Basin), the Atar/El Mreïti Group (Mauritania, Taoudeni Basin) and the Kanpa Formation (Australia, Officer Basin). Thermal maturity of these rock samples is evaluated with Raman geothermometry, Raman reflectance, solid bitumen reflectance, illite crystallinity and Thermal Alteration Index. The comparison of results coming from these different techniques validates the use of Raman reflectance on Proterozoic carbonaceous material and especially for poorly-ordered carbonaceous material. We show that extracted kerogen (microfossils and amorphous organic material) is more accurate to estimate the thermal maturity of low-grade temperature Proterozoic sequences than kerogen in thin section. All techniques provide consistent range of temperatures except for Raman geothermometry, giving slightly higher estimates. Raman reflectance appears to be a fast, robust and non-destructive tool to evaluate the thermal maturity of poorly-organized carbonaceous material from Proterozoic rocks. [less ▲]

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See detailBiosignatures of modern and fossil cyanobacteria
Demoulin, Catherine ULiege; Lara, Yannick ULiege; François, Camille ULiege et al

Poster (2018, March 21)

The Proterozoic is an important eon for the evolution of early life on Earth, and especially for the diversification of cyanobacteria, a major group of photosynthetic microorganisms. In paleontology, much ... [more ▼]

The Proterozoic is an important eon for the evolution of early life on Earth, and especially for the diversification of cyanobacteria, a major group of photosynthetic microorganisms. In paleontology, much effort and work are devoted to the study of cyanobacteria, due to their key-role in the oxygenation of the atmosphere and oceans during the GOE (Great Oxidation Event, around 2.4 Ga). Moreover, the development of oxygenated ecological niches is one of the factors linked to the diversification of eukaryotes. However, identifying extremely old microfossil structures as cyanobacteria remains often disputed. The oldest fossil cyanobacterium (~ 1.9 Ga) determined so far with certainty is Eoentophysalis belcherensis Hofmann, a microorganism forming mats and colonies in silicified stromatolites from the Belcher Islands, Hudson Bay, Canada [1]. Its identification as a cyanobacterium relies mainly on morphological comparison to a modern cyanobacterium, Entophysalis Ercegović [2]. In this context, our research project, financed by the ERC StG ELiTE, mainly aims at characterizing the biosignatures of Proterozoic cyanobacteria in order to get new insights into the origin and early evolution of cyanobacteria and oxygenic phtosynthesis. Methodologically, we are using optical microscopy, electron microscopy (SEM and TEM) and Raman and FTIR microspectroscopy techniques, applied on modern specimens and microfossils. This approach is expected to test the biological nature of Paleoproterozoic and younger microstructures, to resolve the affinities of possible prokaryotic microfossils and, thus, to assess their taxonomic placement among cyanobacteria. [less ▲]

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See detailFTIR micro-spectroscopy: a tool to identify microfossils
Cornet, Yohan ULiege; Javaux, Emmanuelle ULiege

Conference (2018, March 20)

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See detailMicrofossil assemblages from the Paleoproterozoic (Changcheng Group) and Mesoproterozoic (Huailai Group) of North China
Shi, Min; Feng, G; Zhao et al

Conference (2018, March)

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See detailEvidence of Paleoproterozoic plate tectonics: eclogitic subduction
François, Camille ULiege; Debaille, Vinciane; Paquette, Jean-Louis et al

Conference (2018, March)

The question of how and when plate tectonics and subduction processes initiated on Earth is still a subject of debate. Subduction requires the oceanic lithosphere to sustain differential stress without ... [more ▼]

The question of how and when plate tectonics and subduction processes initiated on Earth is still a subject of debate. Subduction requires the oceanic lithosphere to sustain differential stress without creep. Today, mid- to high-pressure mineral assemblages are commonly interpreted in terms of plate tectonic processes including subduction. While in the Early Earth, mid- to high pressure assemblages could have been also produced by sagduction (or stagnant-lid tectonics) of dense mafic lithology into their light silicic crustal basement, the first evidence of high pressure rocks (i.e. eclogites) seems to appear only at the Neoarchean-Paleoproterozoic boundary. In fact, this limit seems to be a crucial period and a time of major change in tectonic style regime. Here, we characterize and date the oldest compelling eclogites discovered so far, dated at 2089 ± 13 Ma from the Northern margin of the Kasai block (Democratic Republic of the Congo). We also identify the protolith of these eclogites as being originally a gabbro formed at 2216 ± 26 Ma in an intra-cratonic rift-type basin, which was buried at high pressure and low temperature (20-25 kbar and 550-600°C) in a subduction zone and then exhumed during a Wilson cycle of ca. 130 Ma, testifying a modern style plate tectonics at 2.2-2.1 Ga. [less ▲]

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See detailThe survival toolkit of the Antarctic cyanobacterium Phormidesmis priestleyi ULC007
Lara, Yannick ULiege; Durieu, Benoit ULiege; Pessi, Igor et al

Conference (2018, March)

Extreme seasonality led by rapid changes in day length and harsh environmental conditions make Antarctica a unique habitat. Freshwater ecosystems range from cryoecosystems and ice shelf meltwater ponds to ... [more ▼]

Extreme seasonality led by rapid changes in day length and harsh environmental conditions make Antarctica a unique habitat. Freshwater ecosystems range from cryoecosystems and ice shelf meltwater ponds to perennially ice-covered lakes where conspicuous benthic microbial mat communities constitute most of the biomass. In these mats, cyanobacteria form the matrix in which other microorganisms can live, and where they are the key primary producers and main drivers of the carbon and food webs[1].
Narrow filamentous cyanobacteria belonging to the order Pseudanabaenales are especially abundant in polar microbial mats [2]. Despite the dominance of cyanobacteria on the Antarctic continent, there is currently no study available on the genomic evolution of Antarctic cyanobacteria. Here we investigate the genome of a widely distributed Antarctic cyanobacterium, Phormidium priestleyi ULC007. To provide a better understanding of the survival strategies of this taxon, we used high-throughput sequencing technologies to investigate its geographic distribution and genome evolution. More precisely, we investigated the abundance of genes in targeted functional categories based on the RAST subsystems technology, so as to provide a better overview of the genetic mechanisms involved in cold adaptation and circadian oscillation [3]. In Polar regions, low temperatures lead to the success of particular organisms featuring adaptations to molecular and cellular disturbances such as rigidity of membranes, reduction of enzyme-catalyzed reactions, and solute transport. Our main results underline the importance of functional categories of genes involved in the production of key molecules for the survival of polar P. priestleyi (e.g. exopolysaccharides, chaperone proteins, fatty acids and phospholipids). [less ▲]

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See detailPolar cyanobacteria in the BCCM/ULC collection : diversity and characterization
Lara, Yannick ULiege; Beets, Kim ULiege; Simons, Véronique et al

Poster (2018, March)

The BCCM/ULC public collection funded by the Belgian Science Policy Office (BELSPO) aims to gather a representative portion of the polar cyanobacterial diversity with different ecological origins (e.g ... [more ▼]

The BCCM/ULC public collection funded by the Belgian Science Policy Office (BELSPO) aims to gather a representative portion of the polar cyanobacterial diversity with different ecological origins (e.g. limnetic microbial mats, soil crusts, cryoconites, endoliths). It makes it available for researchers to study the taxonomy, evolution, adaptation to harsh environmental conditions, and genomic make-up. It presently includes 177 cyanobacterial strains, including 120 of polar origin (catalogue: http://bccm.belspo.be/catalogues/ulc-catalogue-search). Continuous maintenance of living cultures, most of which are also cryopreserved (as back-up), ensure the preservation and the rapid delivery of strains to clients for fundamental and applied research. Genomic DNA is also available on request. The collection has obtained the ISO 9001 certification for deposition and distribution of strains, as part of the multi-site certification for the Belgian Coordinated Collections of Microorganisms (BCCM) consortium. Morphological and molecular identifications (based on SSU rRNA 16S sequences) show that the strains belong to the orders Synechococcales, Oscillatoriales, Pleurocapsales, and Nostocales. This broad ordinal distribution makes the BCCM/ULC collection particularly interesting for phylogenomic studies. Hence, the sequencing of the genomes of several strains is underway. In addition, cyanobacteria produce a range of secondary metabolites (e.g. alkaloides, peptides, polyketides) with different potential bioactivities. Due to their geographic isolation and strong environmental stressors in their habitat, the exploration of Antarctic cyanobacteria metabolites is likely promising for both biotechnology or biomedical applications. [less ▲]

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