| 1. |
- Aguilera, Anabella, et al.
(författare)
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C-ferroptosis is an iron-dependent form of regulated cell death in cyanobacteria
- 2021
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Ingår i: Journal of Cell Biology. - : Rockefeller University Press. - 0021-9525 .- 1540-8140. ; 221:2
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Tidskriftsartikel (refereegranskat)abstract
- Ferroptosis is an oxidative and iron-dependent form of regulated cell death (RCD) recently described in eukaryotic organisms like animals, plants, and parasites. Here, we report that a similar process takes place in the photosynthetic prokaryote Synechocystis sp. PCC 6803 in response to heat stress. After a heat shock, Synechocystis sp. PCC 6803 cells undergo a cell death pathway that can be suppressed by the canonical ferroptosis inhibitors, CPX, vitamin E, Fer-1, liproxstatin-1, glutathione (GSH), or ascorbic acid (AsA). Moreover, as described for eukaryotic ferroptosis, this pathway is characterized by an early depletion of the antioxidants GSH and AsA, and by lipid peroxidation. These results indicate that all of the hallmarks described for eukaryotic ferroptosis are conserved in photosynthetic prokaryotes and suggest that ferroptosis might be an ancient cell death program.
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| 2. |
- Aguilera, Anabella, et al.
(författare)
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Cell death in Cyanobacteria : current understanding and recommendations for a consensus on its nomenclature
- 2021
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Ingår i: Frontiers in Microbiology. - : Frontiers Media S.A.. - 1664-302X. ; 12, s. 1-15
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Forskningsöversikt (refereegranskat)abstract
- Cyanobacteria are globally widespread photosynthetic prokaryotes and are major contributors to global biogeochemical cycles. One of the most critical processes determining cyanobacterial eco-physiology is cellular death. Evidence supports the existence of controlled cellular demise in cyanobacteria, and various forms of cell death have been described as a response to biotic and abiotic stresses. However, cell death research in this phylogenetic group is a relatively young field and understanding of the underlying mechanisms and molecular machinery underpinning this fundamental process remains largely elusive. Furthermore, no systematic classification of modes of cell death has yet been established for cyanobacteria. In this work, we analyzed the state of knowledge in the field of cyanobacterial cell death. Based on that, we propose unified criterion for the definition of accidental, regulated, and programmed forms of cell death in cyanobacteria based on molecular, biochemical, and morphologic aspects following the directions of Nomenclature Committee on Cell Death (NCCD). With this, we aim to provide a guide to standardize the nomenclature related to this topic in a precise and consistent manner, which will facilitate further ecological, evolutionary and applied research in the field of cyanobacterial cell death
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| 3. |
- Aguilera, Anabella, et al.
(författare)
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Cyanobacterial bloom monitoring and assessment in Latin America
- 2023
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Ingår i: Harmful Algae. - : Elsevier. - 1568-9883 .- 1878-1470. ; 125
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Tidskriftsartikel (refereegranskat)abstract
- Cyanobacterial blooms have serious adverse effects on human and environmental health. In Latin America, one of the main world's freshwater reserves, information on this phenomenon remains sparse. To assess the current situation, we gathered reports of cyanobacterial blooms and associated cyanotoxins in freshwater bodies from South America and the Caribbean (Latitude 22 degrees N to 45 degrees S) and compiled the regulation and monitoring procedures implemented in each country. As the operational definition of what is a cyanobacterial bloom remains controversial, we also analyzed the criteria used to determine the phenomena in the region. From 2000 to 2019, blooms were reported in 295 water bodies distributed in 14 countries, including shallow and deep lakes, reservoirs, and rivers. Cyanotoxins were found in nine countries and high concentrations of microcystins were reported in all types of water bodies. Blooms were defined according to different, and sometimes arbitrary criteria including qualitative (changes in water color, scum presence), quantitative (abundance), or both. We found 13 different cell abundance thresholds defining bloom events, from 2 x 10(3) to 1 x 10(7) cells mL(-1). The use of different criteria hampers the estimation of bloom occurrence, and consequently the associated risks and economic impacts. The large differences between countries in terms of number of studies, monitoring efforts, public access to the data and regulations regarding cyanobacteria and cyanotoxins highlights the need to rethink cyanobacterial bloom monitoring, seeking common criteria. General policies leading to solid frameworks based on defined criteria are needed to improve the assessment of cyanobacterial blooms in Latin America. This review represents a starting point toward common approaches for cyanobacterial monitoring and risk assessment, needed to improve regional environmental policies.
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| 4. |
- Aguilera, Anabella, et al.
(författare)
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Do photosynthetic cells communicate with each other during cell death? From cyanobacteria to vascular plants
- 2022
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Ingår i: Journal of Experimental Botany. - : Oxford University Press. - 0022-0957 .- 1460-2431. ; 73:22, s. 7219-7242
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Forskningsöversikt (refereegranskat)abstract
- As in metazoans, life in oxygenic photosynthetic organisms relies on the accurate regulation of cell death. During development and in response to the environment, photosynthetic cells activate and execute cell death pathways that culminate in the death of a specific group of cells, a process known as regulated cell death (RCD). RCD control is instrumental, as its misregulation can lead to growth penalties and even the death of the entire organism. Intracellular molecules released during cell demise may act as ‘survival’ or ‘death’ signals and control the propagation of cell death to surrounding cells, even in unicellular organisms. This review explores different signals involved in cell-cell communication and systemic signalling in photosynthetic organisms, in particular Ca2+, reactive oxygen species, lipid derivates, nitric oxide, and eATP. We discuss their possible mode-of-action as either ‘survival’ or ‘death’ molecules and their potential role in determining cell fate in neighbouring cells. By comparing the knowledge available across the taxonomic spectrum of this coherent phylogenetic group, from cyanobacteria to vascular plants, we aim at contributing to the identification of conserved mechanisms that control cell death propagation in oxygenic photosynthetic organisms
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| 5. |
- Aguilera, Anabella, et al.
(författare)
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Ecophysiological analysis reveals distinct environmental preferences in closely related Baltic Sea picocyanobacteria
- 2023
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Ingår i: Environmental Microbiology. - Chichester : John Wiley & Sons. - 1462-2912 .- 1462-2920. ; 25:9, s. 1674-1695
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Tidskriftsartikel (refereegranskat)abstract
- Cluster 5 picocyanobacteria significantly contribute to primary productivity in aquatic ecosystems. Estuarine populations are highly diverse and consist of many co-occurring strains, but their physiology remains largely understudied. In this study, we characterized 17 novel estuarine picocyanobacterial strains. Phylogenetic analysis of the 16S rRNA and pigment genes (cpcBandcpeBA) uncovered multiple estuarine and freshwater-related clusters and pigment types. Assays with five representative strains (three phycocyanin rich and two phycoerythrin rich) under temperature (10–30°C), light(10–190 μmol photons m-2s-1), and salinity (2–14 PSU) gradients revealed distinct growth optima and tolerance, indicating that genetic variability was accompanied by physiological diversity. Adaptability to environmental conditions was associated with differential pigment content and photosynthetic performance. Amplicon sequence variants at a coastal and an offshore station linked population dynamics with phylogenetic clusters, supporting that strains isolated in this study represent key ecotypes within the Baltic Sea picocyanobacterial community. The functional diversity found within strains with the same pigment type suggests that understanding estuarine picocyanobacterial ecology requires analysis beyond the phycocyanin and phycoerythrin divide. This new knowledge of the environmental preferences in estuarine picocyanobacteria is important for understanding and evaluating productivity in current and future ecosystems.
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| 6. |
- Aguilera, Anabella, et al.
(författare)
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Measurement of Ascorbic Acid and Glutathione Content in Cyanobacterium Synechocystis sp. PCC 6803
- 2020
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Ingår i: Bio-protocol. - : Bio-protocol. - 2331-8325. ; 10:20, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- Ascorbic acid (AsA) and gluthathione (GSH) are two key components of the antioxidant machinery of eukaryotic and prokaryotic cells. The cyanobacterium Synechocystis sp. PCC 6803 presents both compounds in different concentrations (AsA, 20-100 mu M and GSH, 2-5 mM). Therefore, it is important to have precise and sensitive methods to determine the redox status in the cell and to detect variations in this antioxidants. In this protocol, we describe an improved method to estimate the content of both antioxidants (in their reduced and oxidized forms) from the same sample obtained from liquid cultures of Synechocystis sp. PCC 6803.
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| 7. |
- Bhattacharjee, Samujjal, et al.
(författare)
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The hidden world of cyanobacterial cell death : classification, regulatory mechanisms, and ecological significance
- 2024
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Ingår i: Cyanobacteria. - : Elsevier. - 9780443132315 ; , s. 313-340
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Bokkapitel (refereegranskat)abstract
- Cyanobacteria are ancient, globally widespread photosynthetic prokaryotes that synthesize potent toxins and form blooms, a major ecological and human health problem worldwide. Conditions promoting massive bloom proliferation have been extensively studied, but mechanisms causing their abrupt termination are poorly understood. Cell death plays a vital role in the dynamics of ephemeral blooms, determining the flow and fate of organic matter and nutrients. In recent decades, regulated cell death (RCD) induced by biotic or abiotic stresses has become a major mechanism to explain the disappearance of blooms of harmful algal species. However, the molecular basis and physiological mechanisms behind RCD in cyanobacteria are still largely unknown. This chapter aims to describe recent advances in regulated cell death, its nomenclature, implications for cyanobacterial fitness, and ecological relevance. Additionally, we describe methods to study cell demise in this group of photosynthetic organisms. This information contributes to increasing our understanding of how cyanobacteria cope with environmental stress and activate RCD and opens new applications in biotechnology, for instance, the development of new technologies to control harmful blooms and ensuring water quality, and preserve the health of the population.
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| 8. |
- Bonilla, Sylvia, et al.
(författare)
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Nutrients and not temperature are the key drivers for cyanobacterial biomass in the Americas
- 2023
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Ingår i: Harmful Algae. - : Elsevier. - 1568-9883 .- 1878-1470. ; 121
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Tidskriftsartikel (refereegranskat)abstract
- Cyanobacterial blooms imperil the use of freshwater around the globe and present challenges for water man-agement. Studies have suggested that blooms are trigged by high temperatures and nutrient concentrations. While the roles of nitrogen and phosphorus have long been debated, cyanobacterial dominance in phytoplankton has widely been associated with climate warming. However, studies at large geographical scales, covering diverse climate regions and lake depths, are still needed to clarify the drivers of cyanobacterial success. Here, we analyzed data from 464 lakes covering a 14,000 km north-south gradient in the Americas and three lake depth categories. We show that there were no clear trends in cyanobacterial biomass (as biovolume) along latitude or climate gradients, with the exception of lower biomass in polar climates. Phosphorus was the primary resource explaining cyanobacterial biomass in the Americas, while nitrogen was also significant but particularly relevant in very shallow lakes (< 3 m depth). Despite the assessed climatic gradient water temperature was only weakly related to cyanobacterial biomass, suggesting it is overemphasized in current discussions. Depth was critical for predicting cyanobacterial biomass, and shallow lakes proved more vulnerable to eutrophication. Among other variables analyzed, only pH was significantly related to cyanobacteria biomass, likely due to a biologically mediated positive feedback under high nutrient conditions. Solutions toward managing harmful cyanobacteria should thus consider lake morphometric characteristics and emphasize nutrient control, independently of tem-perature gradients, since local factors are more critical - and more amenable to controls - than global external forces.
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| 9. |
- Churakova, Yelena, et al.
(författare)
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Biogenic silica accumulation in picoeukaryotes : Novel players in the marine silica cycle
- 2023
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Ingår i: Environmental Microbiology Reports. - : John Wiley & Sons. - 1758-2229 .- 1758-2229. ; 15:4, s. 282-290
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Tidskriftsartikel (refereegranskat)abstract
- It is well known that the biological control of oceanic silica cycling is dominated by diatoms, with sponges and radiolarians playing additional roles. Recent studies have revealed that some smaller marine organisms (e.g. the picocyanobacterium Synechococcus) also take up silicic acid (dissolved silica, dSi) and accumulate silica, despite not exhibiting silicon dependent cellular structures. Here, we show biogenic silica (bSi) accumulation in five strains of picoeukaryotes (<2-3 mu m), including three novel isolates from the Baltic Sea, and two marine species (Ostreococcus tauri and Micromonas commoda), in cultures grown with added dSi (100 mu M). Average bSi accumulation in these novel biosilicifiers was between 30 and 92 amol Si cell(-1). Growth rate and cell size of the picoeukaryotes were not affected by dSi addition. Still, the purpose of bSi accumulation in these smaller eukaryotic organisms lacking silicon dependent structures remains unclear. In line with the increasing recognition of picoeukaryotes in biogeochemical cycling, our findings suggest that they can also play a significant role in silica cycling.
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| 10. |
- Giannuzzi, Leda, et al.
(författare)
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A Stochastic Characterization of Hydrogen Peroxide-Induced Regulated Cell Death in Microcystis aeruginosa
- 2021
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Ingår i: Frontiers in Microbiology. - : Frontiers Media S.A.. - 1664-302X. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Regulated cell death (RCD) encompasses the activation of cellular pathways that initiate and execute a self-dismissal process. RCD occur over a range of stressors doses that overcome pro-survival cellular pathways, while higher doses cause excessive damage leading to passive accidental cell death (ACD). Hydrogen peroxide (HP) has been proposed as a potential tool to control harmful cyanobacterial blooms, given its capacity to remove cyanobacterial cells and oxidize cyanotoxins. HP is a source of hydroxyl radicals and is expected to induce RCD only within a limited range of concentrations. This property makes this compound very useful to better understand stress-driven RCD. In this work, we analyzed cell death in microcystin-producing Microcystis aeruginosa by means of a stochastic dose response model using a wide range of HP concentrations (0, 0.29, 1.76, 3.67, 7.35, 14.70, and 29.5 mM). We used flow cytometry and unsupervised classification to study cell viability and characterize transitional cell death phenotypes after exposing cells to HP for 48 and 72 h. Non-linear regression was used to fit experimental data to a logistic cumulative distribution function (cdf) and calculate the half maximal effective concentration (EC50). The EC50 of M. aeruginosa exposed to HP were 3.77 +/- 0.26 mM and 4.26 +/- 0.22 mM at 48 and 72 h, respectively. The derivative of cdf (probability density function; pdf) provided theoretical and practical demonstration that EC50 is the minimal dose required to cause RCD in 50% of cells, therefore maximizing the probability of RCD occurrence. 1.76 mM HP lead to an antioxidant stress response characterized by increased reactive oxygen species (ROS) levels and HP decomposition activity. The exposure of 3.67 mM HP induced a dose-related transition in cell death phenotype, and produced several morphological changes (a less dense stroma, distortion of the cell membrane, partial disintegration of thylakoids, extensive cytoplasmic vacuolation and highly condensed chromatin). The EC50 and the stochastic cdf and pdf together with the multidimensional transitional phenotypic analysis of single cells contribute to further characterize cell death pathways in cyanobacteria.
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