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1.
Phytochrome evolution in 3D: deletion, duplication, and diversification.
Rockwell, NC, Lagarias, JC
The New phytologist. 2020;(6):2283-2300
Abstract
Canonical plant phytochromes are master regulators of photomorphogenesis and the shade avoidance response. They are also part of a widespread superfamily of photoreceptors with diverse spectral and biochemical properties. Plant phytochromes belong to a clade including other phytochromes from glaucophyte, prasinophyte, and streptophyte algae (all members of the Archaeplastida) and those from cryptophyte algae. This is consistent with recent analyses supporting the existence of an AC (Archaeplastida + Cryptista) clade. AC phytochromes have been proposed to arise from ancestral cyanobacterial genes via endosymbiotic gene transfer (EGT), but most recent studies instead support multiple horizontal gene transfer (HGT) events to generate extant eukaryotic phytochromes. In principle, this scenario would be compared to the emerging understanding of early events in eukaryotic evolution to generate a coherent picture. Unfortunately, there is currently a major discrepancy between the evolution of phytochromes and the evolution of eukaryotes; phytochrome evolution is thus not a solved problem. We therefore examine phytochrome evolution in a broader context. Within this context, we can identify three important themes in phytochrome evolution: deletion, duplication, and diversification. These themes drive phytochrome evolution as organisms evolve in response to environmental challenges.
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2.
Mixotrophy in marine picocyanobacteria: use of organic compounds by Prochlorococcus and Synechococcus.
Muñoz-Marín, MC, Gómez-Baena, G, López-Lozano, A, Moreno-Cabezuelo, JA, Díez, J, García-Fernández, JM
The ISME journal. 2020;(5):1065-1073
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Abstract
Marine picocyanobacteria of the Prochlorococcus and Synechococcus genera have been longtime considered as autotrophic organisms. However, compelling evidence published over the last 15 years shows that these organisms can use different organic compounds containing key elements to survive in oligotrophic oceans, such as N (amino acids, amino sugars), S (dimethylsulfoniopropionate, DMSP), or P (ATP). Furthermore, marine picocyanobacteria can also take up glucose and use it as a source of carbon and energy, despite the fact that this compound is devoid of limiting elements and can also be synthesized by using standard metabolic pathways. This review will outline the main findings suggesting mixotrophy in the marine picocyanobacteria Prochlorococcus and Synechococcus, and its ecological relevance for these important primary producers.
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3.
Microcystin Incidence in the Drinking Water of Mozambique: Challenges for Public Health Protection.
Tamele, IJ, Vasconcelos, V
Toxins. 2020;(6)
Abstract
Microcystins (MCs) are cyanotoxins produced mainly by freshwater cyanobacteria, which constitute a threat to public health due to their negative effects on humans, such as gastroenteritis and related diseases, including death. In Mozambique, where only 50% of the people have access to safe drinking water, this hepatotoxin is not monitored, and consequently, the population may be exposed to MCs. The few studies done in Maputo and Gaza provinces indicated the occurrence of MC-LR, -YR, and -RR at a concentration ranging from 6.83 to 7.78 µg·L-1, which are very high, around 7 times above than the maximum limit (1 µg·L-1) recommended by WHO. The potential MCs-producing in the studied sites are mainly Microcystis species. These data from Mozambique and from surrounding countries (South Africa, Lesotho, Botswana, Malawi, Zambia, and Tanzania) evidence the need to implement an operational monitoring program of MCs in order to reduce or avoid the possible cases of intoxications since the drinking water quality control tests recommended by the Ministry of Health do not include an MC test. To date, no data of water poisoning episodes recorded were associated with MCs presence in the water. However, this might be underestimated due to a lack of monitoring facilities and/or a lack of public health staff trained for recognizing symptoms of MCs intoxication since the presence of high MCs concentration was reported in Maputo and Gaza provinces.
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4.
Color Sensing and Signal Transmission Diversity of Cyanobacterial Phytochromes and Cyanobacteriochromes.
Villafani, Y, Yang, HW, Park, YI
Molecules and cells. 2020;(6):509-516
Abstract
To perceive fluctuations in light quality, quantity, and timing, higher plants have evolved diverse photoreceptors including UVR8 (a UV-B photoreceptor), cryptochromes, phototropins, and phytochromes (Phys). In contrast to plants, prokaryotic oxygen-evolving photosynthetic organisms, cyanobacteria, rely mostly on bilin-based photoreceptors, namely, cyanobacterial phytochromes (Cphs) and cyanobacteriochromes (CBCRs), which exhibit structural and functional differences compared with plant Phys. CBCRs comprise varying numbers of light sensing domains with diverse color-tuning mechanisms and signal transmission pathways, allowing cyanobacteria to respond to UV-A, visible, and far-red lights. Recent genomic surveys of filamentous cyanobacteria revealed novel CBCRs with broader chromophore-binding specificity and photocycle protochromicity. Furthermore, a novel Cph lineage has been identified that absorbs blue-violet/yellow-orange light. In this minireview, we briefly discuss the diversity in color sensing and signal transmission mechanisms of Cphs and CBCRs, along with their potential utility in the field of optogenetics.
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5.
Antioxidant compounds from microbial sources: A review.
Chandra, P, Sharma, RK, Arora, DS
Food research international (Ottawa, Ont.). 2020;:108849
Abstract
Free radicals are one or more unpaired electrons containing reactive molecules, which can damage nucleic acids, proteins, carbohydrates, and lipids, leading to several diseases including early aging, cancer and atherosclerosis. Antioxidants can scavenge these free radicals to prevent cellular damage by ultimately reducing the oxidative stress and thus have a beneficial effect on human health. Epidemiological studies have already revealed that higher intake of antioxidants as food supplements results in reduced risk of many diseases. Exploring natural antioxidants and its role in human health & nutrition is an emerging field. Several biological sources like medicinal plants, vegetables, spices and fruits have been evaluated as sources of potentially safe natural antioxidants. Beside plants, microorganisms are the potential source of novel bioactive compounds to be used in medical, agricultural, and industrial sectors. As compared to plants, microbes can be grown under controlled conditions at a faster rate, which make them a potential source of natural bioactive molecules for food and nutraceutical applications. This review summarizes the potential of different microorganisms including actinomycetes, bacteria, blue green algae, fungi, lichens and mushrooms to be explored as the source of such bioactive compounds.
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6.
Cyanobacterial aldehyde deformylating oxygenase: Structure, function, and potential in biofuels production.
Basri, RS, Rahman, RNZRA, Kamarudin, NHA, Ali, MSM
International journal of biological macromolecules. 2020;:3155-3162
Abstract
The conversion of aldehydes to valuable alkanes via cyanobacterial aldehyde deformylating oxygenase is of great interest. The availability of fossil reserves that keep on decreasing due to human exploitation is worrying, and even more troubling is the combustion emission from the fuel, which contributes to the environmental crisis and health issues. Hence, it is crucial to use a renewable and eco-friendly alternative that yields compound with the closest features as conventional petroleum-based fuel, and that can be used in biofuels production. Cyanobacterial aldehyde deformylating oxygenase (ADO) is a metal-dependent enzyme with an α-helical structure that contains di‑iron at the active site. The substrate enters the active site of every ADO through a hydrophobic channel. This enzyme exhibits catalytic activity toward converting Cn aldehyde to Cn-1 alkane and formate as a co-product. These cyanobacterial enzymes are small and easy to manipulate. Currently, ADOs are broadly studied and engineered for improving their enzymatic activity and substrate specificity for better alkane production. This review provides a summary of recent progress in the study of the structure and function of ADO, structural-based engineering of the enzyme, and highlight its potential in producing biofuels.
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7.
Far-red light acclimation in diverse oxygenic photosynthetic organisms.
Wolf, BM, Blankenship, RE
Photosynthesis research. 2019;(3):349-359
Abstract
Oxygenic photosynthesis has historically been considered limited to be driven by the wavelengths of visible light. However, in the last few decades, various adaptations have been discovered that allow algae, cyanobacteria, and even plants to utilize longer wavelength light in the far-red spectral range. These adaptations provide distinct advantages to the species possessing them, allowing the effective utilization of shade light under highly filtered light environments. In prokaryotes, these adaptations include the production of far-red-absorbing chlorophylls d and f and the remodeling of phycobilisome antennas and reaction centers. Eukaryotes express specialized light-harvesting pigment-protein complexes that use interactions between pigments and their protein environment to spectrally tune the absorption of chlorophyll a. If these adaptations could be applied to crop plants, a potentially significant increase in photon utilization in lower shaded leaves could be realized, improving crop yields.
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8.
Bioinspired biomolecules: Mycosporine-like amino acids and scytonemin from Lyngbya sp. with UV-protection potentialities.
Fuentes-Tristan, S, Parra-Saldivar, R, Iqbal, HMN, Carrillo-Nieves, D
Journal of photochemistry and photobiology. B, Biology. 2019;:111684
Abstract
Since the beginning of life on Earth, cyanobacteria have been exposed to natural ultraviolet-A radiation (UV-A, 315-400 nm) and ultraviolet-B radiation (UV-B, 280-315 nm), affecting their cells' biomolecules. These photoautotrophic organisms have needed to evolve to survive and thus, have developed different mechanisms against ultraviolet radiation. These mechanisms include UVR avoidance, DNA repair, and cell protection by producing photoprotective compounds like Scytonemin, carotenoids, and Mycosporine-like amino acids (MAAs). Lyngbya marine species are commercially important due to their secondary metabolites that show a range of biological activities including antibacterial, insecticidal, anticancer, antifungal, and enzyme inhibitor. The main topic in this review covers the Lyngbya sp., a cyanobacteria genus that presents photoprotection provided by the UV-absorbing/screening compounds such as MAAs and Scytonemin. These compounds have considerable potentialities to be used in the cosmeceutical, pharmaceutical, biotechnological and biomedical sectors and other related manufacturing industries with an additional value of environment friendly in nature. Scytonemin has UV protectant, anti-inflammatory, anti-proliferative, and antioxidant activity. MAAs act as sunscreens, provide additional protection as antioxidants, can be used as UV protectors, activators of cell proliferation, skin-care products, and even as photo-stabilizing additives in paints, plastics, and varnishes. The five MAAs identified so far in Lyngbya sp. are Asterina-330, M-312, Palythine, Porphyra-334, and Shinorine are capable of dissipating absorbed radiation as harmless heat without producing reactive oxygen species.
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9.
Soil microalgae and cyanobacteria: the biotechnological potential in the maintenance of soil fertility and health.
Abinandan, S, Subashchandrabose, SR, Venkateswarlu, K, Megharaj, M
Critical reviews in biotechnology. 2019;(8):981-998
Abstract
The soil microbiota plays a major role in maintaining the nutrient balance, carbon sink, and soil health. Numerous studies reported on the function of microbiota such as plant growth-promoting bacteria and fungi in soil. Although microalgae and cyanobacteria are ubiquitous in soil, very less attention has been paid on the potential of these microorganisms. The indiscriminate use of various chemicals to enhance agricultural productivity led to serious consequences like structure instability, accumulation of toxic contaminants, etc., leading to an ecological imbalance between soil, plant, and microbiota. However, the significant role of microalgae and cyanobacteria in crop productivity and other potential options has been so far undermined. The intent of the present critical review is to highlight the significance of this unique group of microorganisms in terms of maintaining soil fertility and soil health. Beneficial soil ecological applications of these two groups in enhancing plant growth, establishing interrelationships among other microbes, and detoxifying chemical agents such as insecticides, herbicides, etc. through mutualistic cooperation by synthesizing enzymes and phytohormones are presented. Since recombinant technology involving genomic integration favors the development of useful traits in microalgae and cyanobacteria for their potential application in improvement of soil fertility and health, the merits and demerits of various such advanced methodologies associated in harnessing the biotechnological potential of these photosynthetic microorganisms for sustainable agriculture were also discussed.
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10.
Selection of cyanobacteria over green algae in a photo-sequencing batch bioreactor fed with wastewater.
Arias, DM, Rueda, E, García-Galán, MJ, Uggetti, E, García, J
The Science of the total environment. 2019;:485-495
Abstract
In this work, a strategy based on photo-sequencing batch operation was used to select cyanobacteria over unsettled green algae in a wastewater treatment system, evaluating for the first time the effect of hydraulic regimes on nutritional dynamics and microorganisms' competition. During 30 days of operation, an initial microalgae mixed consortia dominated by the green microalgae Scenedesmus sp. was cultivated in two different photo-sequencing batch reactors operated at hydraulic retention time (HRT) of 6 days (PSBR6) and 4 days (PSBR4) at a theoretical solids retention time (SRT) of 10 d. Both reactors were compared with a semi-continuous reactor (SC10) operated at 10 d of HRT and 10 days of SRT (used as a control). The results indicated that PSBR6 and PSBR4 decreased Scenedesmus sp. population by 88% and 48%, respectively. However, only PSBR6 provided suitable conditions to select cyanobacteria from an initial green algae dominated culture. These conditions included volumetric loads of 11.72 mg TN L-1 d-1, 2.04 mg TP L-1 d-1 and 53.31 mg TOC L-1 d-1. The remaining nutrients in the culture led also to a phosphorus limiting N:P ratio (34:1) that improved the increase of cyanobacteria from an initial 2% until 70% of the total population. In addition, PSBR6 reached a biomass production of 0.12 g L-1 d-1, while removing TN, TP and TOC by 58%, 83% and 85%, respectively. Conversely, the application of higher nutrients loads caused by lower HRT (PSBR4) led to an increase of only 13% of cyanobacteria while SC10 remained with the same biomass composition during all the experimental time. Thus, this study showed that the dominance of cyanobacteria in microalgal-based wastewater treatment systems can be controlled by the operational and nutritional conditions. This knowledge could contribute to control microalgae contamination from up-scaling cyanobacterial biomass production in wastewater treatment systems.