Mycosporine-Like Amino Acids and Marine Toxins - The Common and the Different

Marine microorganisms harbor a multitude of secondary metabolites. Among these are toxins of different chemical classes as well as the UV-protective mycosporine-like amino acids (MAAs). The latter form a group of water-soluble, low molecular-weight (generally < 400) compounds composed of either an aminocyclohexenone or an aminocyclohexenimine ring, carrying amino acid or amino alcohol substituents. So far there has been no report of toxicity in MAAs but nevertheless there are some features they have in common with marine toxins. Among the organisms producing MAAs are cyanobacteria, dinoflagellates and diatoms that also synthesize toxins. As in cyclic peptide toxins found in cyanobacteria, amino acids are the main building blocks of MAAs. Both, MAAs and some marine toxins are transferred to other organisms e.g. via the food chains, and chemical modifications can take place in secondary consumers. In contrast to algal toxins, the physiological role of MAAs is clearly the protection from harmful UV radiation by physical screening. However, other roles, e.g. as osmolytes and antioxidants, are also considered. In this paper the common characteristics of MAAs and marine toxins are discussed as well as the differences

Dinámicas de fotoinhibición y reorganización pigmentaria bajo ciclos de luz/oscuridad como mecanismos de fotoprotección en Porphyra umbilicales frente a los efectos dañinos de la radiación ultravioleta

Porphyra umbilicalis L. Kutzing collected from the upper intertidal zone at Helgoland, North Sea, was exposed to different spectral ranges of UV radiation under both 12/12 h light/dark cycles and continuous irradiation. In light/dark cycles, oscillations of the optimal quantum yield (Fv /Fm) were observed during the experiments, reaching maximal values at the end of the light phase followed by lower values during the dark phase. Decreased Fv /Fm was observed in thalli illuminated with photosynthetic active radiation (PAR) plus UV-A and PAR+UV-A+UV-B, compared with the PAR control, indicating a certain degree of UV-induced photoinhibition. In addition, a decrease in the percentage of change of the linear initial slope and maximum electron transport rate (ETR) estimated from ETR vs. irradiance curves was induced by UV radiation during the light phase. Recovery during the 12 h dark phase was almost completed in UV-A treated plants. PAR+UV-A seemed not to affect the photosynthesis, measured as O2 production. However, a decrease in O2 production was observed in the PAR+UV-A+UV-B treatment, but it recovered to initial values after 48 h of culture. No changes in total content of photosynthetic pigments were observed. However, thallus absorptance and the in vivo absorption cross-section in the PAR range (400-700 nm) normalised to Chl a (a* parameter) fluctuated during light/dark cycles and were positively correlated with changes in the optimum quantum yield, thus indicating that daily pigment reorganisation in the light-harvesting complex may play a key role in the photosynthetic performance of the algae. Both UV-A and UV-B treatments under continuous irradiation induced a significant reduction in the optimal quantum yield, ETR efficiency and photosynthetic oxygen production during the first 36 h to values around 30% of the initial ones. Thus, different protective mechanisms against UV stress can be observed in P. umbilicalis: dynamic photoinhibition when UVA is combined with PAR, followed by full recovery of photosynthesis during the dark phase, and a more pronounced photoinhibition under UV-B, with only partial recovery after longer time periods, in which photosynthetic pigment reorganisation plays an important role.Talos del alga roja Porphyra umbilicales L. Kutzing fueron cultivados bajo diferentes condiciones espectrales de radiación ultravioleta en condiciones de ciclos de luz/oscuridad de 12 horas y bajo luz continua. El rendimiento cuántico óptimo (Fv /Fm), estimado a través de la fluorescencia de la clorofila a del fotosistema II, evolucionó con oscilaciones en los ciclos de luz/oscuridad, con valores máximos al final de cada fase de luz seguida de valores bajos a lo largo de la fase de oscuridad. Los cultivos iluminados bajo radiación fotosintéticamente activa (PAR)+UV-A y la PAR+UV-A+UV-B disminuyeron los valores de la relación (Fv /Fm) respecto a los cultivos bajo PAR. Los cultivos bajo radiación UV provocaron además una caída, durante la fase de luz, tanto de la pendiente inicial como de los valores máximos de la tasa de transporte electrónico (ETR) estimados a partir de las curvas ETR vs. irradiancia. En el caso de los cultivos bajo PAR + UV-A la recuperación de los valores fotosintéticos fue casi completa durante la fase de oscuridad. Dicho tratamiento no afectó a la producción fotosintética de O2 mientras que el cultivo bajo PAR+UV-A+UV-B disminuyó significativamente dicha tasa, la cual recuperó los valores iniciales tras 48 h de cultivo. No se observaron cambios en el contenido total de los pigmentos fotosintéticos. No obstante, los ciclos de luz/oscuridad afectaron tanto a la absorptancia de los talos como a los valores de corte transversal in vivo en el rango del PAR (400-700 podría implicar un papel clave en el mantenimiento de la actividad fotosintética del alga. En cambio, el cultivo de los talos en luz continua bajo los tratamientos de radiación UV-A y UV-B provocó una disminución del rendimiento cuántico óptimo, de la eficiencia del ETR y de la tasa fotosintética por producción de oxígeno durante las primeras 36 h llegando a valores del 30% de los valores iniciales. Por tanto, diferentes mecanismos están implicados en la protección frente al estrés por radiación ultravioleta en P. umbilicales; un mecanismo de fotoinhibición dinámica cuando el UV-A se combina con el PAR, el cual es seguido por una recuperación completa de los parámetros fotosintéticos durante la posterior fase de oscuridad, y una fotoinhibición más patente en el caso del cultivo bajo UV-B, la cual se recupera sólo parcialmente tras un período largo. En ambos casos, la reorganización de los pigmentos fotosintéticos juega un papel fundamental en dicha recuperación

Genome mining of mycosporine-like amino acid (MAA) synthesizing and non-synthesizing cyanobacteria: A bioinformatics study

AbstractMycosporine-like amino acids (MAAs) are a family of more than 20 compounds having absorption maxima between 310 and 362 nm. These compounds are well known for their UV-absorbing/screening role in various organisms and seem to have evolutionary significance. In the present investigation we tested four cyanobacteria, e.g., Anabaena variabilis PCC 7937, Anabaena sp. PCC 7120, Synechocystis sp. PCC 6803 and Synechococcus sp. PCC 6301, for their ability to synthesize MAA and conducted genomic and phylogenetic analysis to identify the possible set of genes that might be involved in the biosynthesis of these compounds. Out of the four investigated species, only A. variabilis PCC 7937 was able to synthesize MAA. Genome mining identified a combination of genes, YP_324358 (predicted DHQ synthase) and YP_324357 (O-methyltransferase), which were present only in A. variabilis PCC 7937 and missing in the other studied cyanobacteria. Phylogenetic analysis revealed that these two genes are transferred from a cyanobacterial donor to dinoflagellates and finally to metazoa by a lateral gene transfer event. All other cyanobacteria, which have these two genes, also had another copy of the DHQ synthase gene. The predicted protein structure for YP_324358 also suggested that this product is different from the chemically characterized DHQ synthase of Aspergillus nidulans contrary to the YP_324879, which was predicted to be similar to the DHQ synthase. The present study provides a first insight into the genes of cyanobacteria involved in MAA biosynthesis and thus widens the field of research for molecular, bioinformatics and phylogenetic analysis of these evolutionary and industrially important compounds. Based on the results we propose that YP_324358 and YP_324357 gene products are involved in the biosynthesis of the common core (deoxygadusol) of all MAAs

Photoactivated Adenylyl Cyclase Controls Phototaxis in the Flagellate Euglena gracilis

Euglena gracilis, a unicellular freshwater protist exhibits different photomovement responses, such as phototaxis (oriented movement toward or away from the light source) and photophobic (abrupt turn in response to a rapid increase [step-up] or decrease [step-down] in the light fluence rate) responses. Photoactivated adenylyl cyclase (PAC) has been isolated from whole-cell preparations and identified by RNA interference (RNA) to be the photoreceptor for step-up photophobic responses but not for step-down photophobic responses (M. Iseki, S, Matsunaga, A. Murakami, K. Ohno, K. Shiga, C. Yoshida, M. Sugai, T. Takahashi, T. Hori, M. Watanabe [2002] Nature 415: 1047-1051). The present study shows that knockdown of PAC by RNAi also effectively suppresses both positive and negative phototaxis, indicating for the first time that PAC or a PAC homolog is also the photoreceptor for photoorientation of wild-type E. gracilis. Recovery from RNAi occurred earlier for step-up photophobic responses than for positive and negative phototaxis. In addition, we investigated several phototaxis mutant strains of E. gracilis with different cytological features regarding the stigma and paraxonemal body (PAB; believed to be the location for the phototaxis photoreceptor) as well as Astasia longa, a close relative of E. gracilis. All of the E. gracilis mutant strains had PAC mRNAs, whereas in A. longa, a different but similar mRNA was found and designated AlPAC. Consistently, all of these strains showed no photo taxis but performed step-up photophobic responses, which were suppressed by RNAi of the PAC mRNA. The fact that some of these strains possess a cytologically altered or no PAB demonstrates that at least in these strains, the PAC photoreceptor responsible for the step-up photophobic responses is not located in the PAB

ISS RADIATION ENVIRONMENT AS OBSERVED BY LIULIN TYPE-R3DR2 INSTRUMENT IN OCTOBER-NOVEMBER 2014

Space radiation was monitored using the R3DR2 spectrometer-dosimeter during the flight outside the Russian “Zvezda” module of ISS in October-November 2014. The instrument was mounted on the ESA EXPOSE-R2 platform. The R3DR2 instrument was first developed and used during the flight of ESA EXPOSE-R platform in 2009-2010 (Dachev et al, 2015a). It is a low mass, small dimension automated device that measures solar visible and ultraviolet (UV) radiation in four channels and ionizing radiation in 256 channels of a Liulin-type energy deposition spectrometer (Dachev et al, 2002). Ionizing radiation was measured and separated in 256 deposited energy spectra, which were further used for determination of the absorbed dose rate and flux. The main results obtained by the R3DR2 instrument are: (1) three different radiation sources were detected and quantified - galactic cosmic rays (GCR), energetic protons from the inner radiation belt (IRB) in the region of the South Atlantic anomaly and energetic electrons from the outer radiation belt (ORB); (2) for the first time in the history of using of the Liulin-type energy deposition spectrometers (Dachev et al, 2015b) an observable flux from solar energetic particles (SEP) was detected in the period 1-4 November 2014; (3) the obtained SEP energy deposition spectra were compared with other spectra to confirm their shape

Combined impact of ultraviolet radiation and increased nutrients supply: a test of the potential anthropogenic impacts on the benthic amphipod Amphitoe valida from Patagonian waters (Argentina)

Experiments were conducted during the Austral Summer of 2014 to determine the effects of increased nutrient input and ultraviolet radiation (UVR) on the food consumption rate (FCR) and food preference in the amphipod Amphitoe valida. We collected specimens from the Patagonian coast (Argentina), from beaches close (Barrancas Blancas; BB) and further away (Cangrejales; C) from the Chubut River, which constitutes the potential source of eutrophication. Organisms were exposed to different radiation regimes (full radiation vs. PAR only) and fed with different macroalgae diets (i.e., from different geographical location and with different quality in terms on nutrient content). Males collected from C showed food compensation, consuming more food under low-nutrient diets, while no compensation was observed in males from BB. Regardless of their origin, UVR decreased the FCR when males where fed on ambient nutrient diets, but not when males fed on high-quality diets indicating that in the former case, individuals were in worse physiological conditions to cope with UVR; food quality, however, significantly counteracted the deleterious effects of UVR on FCR. Females collected from the two beaches showed similar FCR under high-nutrient diet and had no food compensation when fed in low-nutrient diets. Females were more vulnerable to UVR, since their FCR were lower when exposed to UV radiation independent of the diet. Our results show that under anthropogenic eutrophication and high solar UVR levels an increase in the nutrient input could favor only males of A. valida , by reducing the negative effects of UVR on their FCR. Nevertheless, these nutrient inputs might cause additional problems like anoxia, as a result of an unusual macroalgal growth, thus affecting amphipod’s survival.Fil: Valiñas, Macarena Soledad. Fundación Playa Unión. Estación de Fotobiología Playa Unión; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bermejo, Paula. Fundación Playa Unión. Estación de Fotobiología Playa Unión; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Galbán, Lara. Fundación Playa Unión. Estación de Fotobiología Playa Unión; ArgentinaFil: Laborda, Luciana. Fundación Playa Unión. Estación de Fotobiología Playa Unión; ArgentinaFil: Häder, Donat P.. Universitat Erlangen-Nuremberg; AlemaniaFil: Villafañe, Virginia Estela. Fundación Playa Unión. Estación de Fotobiología Playa Unión; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Helbling, Eduardo Walter. Fundación Playa Unión. Estación de Fotobiología Playa Unión; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Approaches to Assess the Suitability of Zooplankton for Bioregenerative Life Support Systems

Future manned space exploration will send humans farther away from Earth than ever before (e.g., to Mars), leading to extended mission durations and thus to a higher demand for essentials such as food, water and oxygen. As resupplying these items from Earth is nearly impossible, aquatic bioregenerative life support systems (BLSS) appear to be a promising solution. Due to its central role in aquatic ecosystems, zooplankton could act as a key player in aquatic BLSS, linking oxygen liberating, autotrophic producers and higher trophic levels. However, prior to the utilization of BLSS in space, organisms proposed to inhabit these systems have to be studied thoroughly to evaluate any space-borne adverse traits, which may impede a proper function of the system. To investigate the impact of microgravity (μg), in particular, several platforms are available, providing μg periods ranging from seconds (Bremen drop tower and parabolic flights), to minutes (sounding rockets), up to even days and months (space flights and the International Space Station (ISS)). Furthermore, ground-based facilities, such as clinostats, enable the of candidate organisms to variable periods of simulated/functional μg. In this book chapter, research on zooplankton utilizing these methods is summarized

Effects of UV radiation on aquatic ecosystems and interactions with other environmental factors

Interactions between climate change and UV radiation are having strong effects on aquatic ecosystems due to feedback between temperature, UV radiation, and greenhouse gas concentration. Higher air temperatures and incoming solar radiation are increasing the surface water temperatures of lakes and oceans, with many large lakes warming at twice the rate of regional air temperatures. Warmer oceans are changing habitats and the species composition of many marine ecosystems. For some, such as corals, the temperatures may become too high. Temperature differences between surface and deep waters are becoming greater. This increase in thermal stratification makes the surface layers shallower and leads to stronger barriers to upward mixing of nutrients necessary for photosynthesis. This also results in exposure to higher levels of UV radiation of surface-dwelling organisms. In polar and alpine regions decreases in the duration and amount of snow and ice cover on lakes and oceans are also increasing exposure to UV radiation. In contrast, in lakes and coastal oceans the concentration and colour of UV-absorbing dissolved organic matter (DOM) from terrestrial ecosystems is increasing with greater runoff from higher precipitation and more frequent extreme storms. DOM thus creates a refuge from UV radiation that can enable UV-sensitive species to become established. At the same time, decreased UV radiation in such surface waters reduces the capacity of solar UV radiation to inactivate viruses and other pathogens and parasites, and increases the difficulty and price of purifying drinking water for municipal supplies. Solar UV radiation breaks down the DOM, making it more available for microbial processing, resulting in the release of greenhouse gases into the atmosphere. In addition to screening solar irradiance, DOM, when sunlit in surface water, can lead to the formation of reactive oxygen species (ROS). Increases in carbon dioxide are in turn acidifying the oceans and inhibiting the ability of many marine organisms to form UV-absorbing exoskeletons. Many aquatic organisms use adaptive strategies to mitigate the effects of solar UV-B radiation (280–315 nm), including vertical migration, crust formation, synthesis of UV-absorbing substances, and enzymatic and non-enzymatic quenching of ROS. Whether or not genetic adaptation to changes in the abiotic factors plays a role in mitigating stress and damage has not been determined. This assessment addresses how our knowledge of the interactive effects of UV radiation and climate change factors on aquatic ecosystems has advanced in the past four years.Fil: Häder, Donat P.. Universitat Erlangen-Nuremberg; AlemaniaFil: Williamson, Craig E.. Miami University; Estados UnidosFil: Wängberg, Sten Åke. University of Gothenburg. Department of Biological and Environmental Science; SueciaFil: Rautio, Milla. Université du Québec à Chicoutimi. Département des Sciences Fondamentales and Centre for Northern Studies; CanadáFil: Rose, Kevin C.. University Of Wisconsin; Estados UnidosFil: Gao, Kunshan. Xiamen University. State Key Laboratory of Marine Environmental Science; ChinaFil: Helbling, Eduardo Walter. Fundación Playa Unión. Estación de Fotobiología Playa Unión; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Sinha, Rajeshwar P.. Banaras Hindu University. Centre of Advanced Study in Botany; IndiaFil: Worrest, Robert. Columbia University; Estados Unido

Complementary UV-Absorption of Mycosporine-like Amino Acids and Scytonemin is Responsible for the UV-Insensitivity of Photosynthesis in Nostoc flagelliforme

Mycosporine-like amino acids (MAAs) and scytonemin are UV-screening compounds that have presumably appeared early in the history of life and are widespread in cyanobacteria. Natural colonies of the UV-insensitive Nostoc flagelliforme were found to be especially rich in MAAs (32.1 mg g DW−1), concentrated in the glycan sheath together with scytonemin. MAAs are present in the form of oligosaccharide-linked molecules. Photosystem II activity, measured using PAM fluorescence and oxygen evolution, was used as a most sensitive physiological parameter to analyse the effectiveness of UV-protection. Laboratory experiments were performed under controlled conditions with a simulated solar radiation specifically deprived of UV-wavebands with cut-off filters (295, 305, 320, 345 and 395 nm). The UV-insensitivity of N. flagelliforme was found to cover the whole UV-A (315–400 nm) and UV-B (280–320 nm) range and is almost certainly due to the complementary UV-absorption of MAAs and scytonemin. The experimental approach used is proposed to be suitable for the comparison of the UV-protection ability in organisms that differ in their complement of UV-sunscreen compounds. Furthermore, this study performed with a genuinely terrestrial organism points to the relevance of marine photoprotective compounds for life on Earth, especially for the colonization of terrestrial environments

Plastics in the environment in the context of UV radiation, climate change and the Montreal Protocol: UNEP Environmental Effects Assessment Panel, Update 2023

This Assessment Update by the Environmental Effects Assessment Panel (EEAP) of the United Nations Environment Programme (UNEP) considers the interactive effects of solar UV radiation, global warming, and other weathering factors on plastics. The Assessment illustrates the significance of solar UV radiation in decreasing the durability of plastic materials, degradation of plastic debris, formation of micro- and nanoplastic particles and accompanying leaching of potential toxic compounds. Micro- and nanoplastics have been found in all ecosystems, the atmosphere, and in humans. While the potential biological risks are not yet well-established, the widespread and increasing occurrence of plastic pollution is reason for continuing research and monitoring. Plastic debris persists after its intended life in soils, water bodies and the atmosphere as well as in living organisms. To counteract accumulation of plastics in the environment, the lifetime of novel plastics or plastic alternatives should better match the functional life of products, with eventual breakdown releasing harmless substances to the environment