Mycosporine-Like Amino Acids as Multifunctional Secondary Metabolites in Cyanobacteria: From Biochemical to Application Aspects

Microalgae-assisted green bioremediation of food-processing wastewater: A sustainable approach toward a circular economy concept

Wastewater disposal is a major environmental issue that pollutes water, causing eutrophication, habitat destruction, and economic impact. In Mexico, food-processing effluents pose a huge environmental threat due to their excessive nutrient content and their large volume discharged every year. Some of the most harmful residues are tequila vinasses, nejayote, and cheese whey. Each liter of tequila generates 13-15 L of vinasses, each kilogram of cheese produces approximately 9 kg of cheese whey, and each kilogram of nixtamalized maize results in the production of 2.5-3.3 L of nejayote. A promising strategy to reduce the contamination derived from wastewater is through microalgae-based wastewater treatment. Microalgae have a high adaptability to hostile environments and they can feed on the nutrients in the effluents to grow. Moreover, to increase the viability, profitability, and value of wastewater treatments, a microalgae biorefinery could be proposed. This review will focus on the circular bioeconomy scheme focused on the simultaneous food-processing wastewater treatment and its use to grow microalgae biomass to produce added-value compounds. This strategy allows for the revalorization of wastewater, decreases contamination of water sources, and produces valuable compounds that promote human health such as phycobiliproteins, carotenoids, omega-3 fatty acids, exopolysaccharides, mycosporine-like amino acids, and as a source of clean energy: biodiesel, biogas, and bioethanol.

Metabolic flux phenotyping of secondary metabolism in cyanobacteria

Cyanobacteria generate energy from photosynthesis and produce various secondary metabolites with diverse commercial and pharmaceutical applications. Unique metabolic and regulatory pathways in cyanobacteria present new challenges for researchers to enhance their product yields, titers, and rates. Therefore, further advancements are critically needed to establish cyanobacteria as a preferred bioproduction platform. Metabolic flux analysis (MFA) quantitatively determines the intracellular flows of carbon within complex biochemical networks, which elucidate the control of metabolic pathways by transcriptional, translational, and allosteric regulatory mechanisms. The emerging field of systems metabolic engineering (SME) involves the use of MFA and other omics technologies to guide the rational development of microbial production strains. This review highlights the potential of MFA and SME to optimize the production of cyanobacterial secondary metabolites and discusses the technical challenges that lie ahead.

Isolation and Structure Elucidation of Novel Mycosporine-like Amino Acids from the Two Intertidal Red Macroalgae Bostrychia scorpioides and Catenella caespitosa

This study presents a phytochemical survey of two common intertidal red algal species, Bostrychia scorpioides and Catenella caespitosa, regarding their MAA (mycosporine-like amino acid) composition, which are known as biogenic sunscreen compounds. Six novel MAAs from Bostrychia scorpioides named bostrychines and two novel MAAs from Catenella caespitosa named catenellines were isolated using a protocol which included silica gel column chromatography, flash chromatography on reversed phase material and semipreparative HPLC (High-Performance Liquid Chromatography). The structure of the novel MAAs was elucidated using NMR (Nuclear Magnetic Resonance) and HR-MS (High-Resolution Mass Spectrometry), and their absolute configuration was confirmed by ECD (Electronic Circular Dichroism). All isolated MAAs possess a cyclohexenimine scaffold, and the metabolites from B. scorpioides are related to the known MAAs bostrychines A-F, which contain glutamine, glutamic acid and/or threonine in their side chains. The new MAAs from C. caespitosa contain taurine, an amino sulfonic acid that is also present in another MAA isolated from this species, namely, catenelline. Previous and new data confirm that intertidal red algae are chemically rich in MAAs, which explains their high tolerance against biologically harmful ultraviolet radiation.

Halotolerance, stress mechanisms, and circadian clock of salt-tolerant cyanobacteria

Cyanobacteria harbor a high level of physiological flexibility, which enables them to reside in virtually all available environmental niches, including extreme environments. In this review, we summarize the recent advancements in stress mechanisms of salt-tolerant (a.k.a. halotolerant) cyanobacteria. Omics approaches have been extensively employed in recent years to decipher mechanisms of halotolerance and to understand the relevance of halotolerance-associated gene regulatory networks. The vast knowledge from genome mining disclosed that halotolerant cyanobacteria possess extended gene families and/or clusters, encoding enzymes that synthesize unique osmoprotectants, including glycine betaine (GB), betaine derivatives, and mycosporine-like amino acids (MAAs). Comprehensive transcriptomic analyses were conducted using Halothece sp. PCC7418 (hereafter referred to as Halothece), a cyanobacterium that exhibits remarkable halotolerance. These studies revealed a specific transcriptional response when Halothece was subjected to salt stress, whereas salt and osmotic stresses were found to share a common transcriptomic response. Transcriptome and metabolite analyses of Halothece illustrated a complex dynamic relationship between the biosyntheses of osmoprotectants, as well as corresponding and ancillary pathways. Lastly, novel insights highlight the relationship between the molecular regulation of the circadian rhythm and salt stress tolerance. Since the circadian rhythm of gene expression was distorted under salt stress, halotolerant cyanobacteria may prioritize the adaptation to salt stress by attenuation of circadian rhythmicity. KEY POINTS: • Recent advancements in the understanding of stress mechanisms in halotolerant cyanobacteria are described based on omics analyses. • Transcriptome and metabolite analyses of Halothece illustrated a complex dynamic relationship between the biosyntheses of osmoprotectants, as well as corresponding and ancillary pathways. • Since salt stress affects the molecular regulation among clock-related proteins, salt stress may attenuate circadian rhythmicity.

Global transcriptional and circadian regulation in a halotolerant cyanobacterium Halothece sp. PCC7418

Substantial evidence has been accumulated about the molecular basis underlying halotolerance; however, insights into the regulatory networks for relevant genes and mechanisms of their interplay remain elusive. Here, we present a comprehensive transcriptome investigation, using RNA sequencing, of specific metabolic pathways and networks in a halotolerant cyanobacterium, Halothece sp. PCC7418, including the circadian rhythm profile. Dissecting the transcriptome presented the intracellular regulation of gene expressions, which was linked with ion homeostasis, protein homeostasis, biosynthesis of compatible solutes, and signal transduction, for adaptations to high-salinity environments. The efficient production and distribution of energy were also implicated in this acclimation process. Furthermore, we found that high-salinity environments had a dramatic effect on the global transcriptional expression regulated by the circadian clock. Our findings can provide a comprehensive transcriptome for elucidating the molecular mechanisms underlying halotolerance in cyanobacteria.

Microalgae as a Source of Mycosporine-like Amino Acids (MAAs); Advances and Future Prospects

Mycosporine-like amino acids (MAAs), are secondary metabolites, first reported in 1960 and found to be associated with the light-stimulated sporulation in terrestrial fungi. MAAs are nitrogenous, low molecular weight, water soluble compounds, which are highly stable with cyclohexenone or cycloheximine rings to store the free radicals. Microalgae are considered as a good source of different kinds of MAAs, which in turn, has its own applications in various industries due to its UV absorbing, anti-oxidant and therapeutic properties. Microalgae can be easily cultivated and requires a very short generation time, which makes them environment friendly source of biomolecules such as mycosporine-like amino acids. Modifying the cultural conditions along withmanipulation of genes associated with mycosporine-like amino acids biosynthesis can help to enhance MAAs synthesis and, in turn, can make microalgae suitable bio-refinery for large scale MAAs production. This review focuses on properties and therapeutic applications of mycosporine like amino acids derived from microalgae. Further attention is drawn on various culture and genetic engineering approaches to enhance the MAAs production in microalgae.

Bioactive Metabolites Produced by Cyanobacteria for Growth Adaptation and Their Pharmacological Properties

Cyanobacteria are the most abundant oxygenic photosynthetic organisms inhabiting various ecosystems on earth. As with all other photosynthetic organisms, cyanobacteria release oxygen as a byproduct during photosynthesis. In fact, some cyanobacterial species are involved in the global nitrogen cycles by fixing atmospheric nitrogen. Environmental factors influence the dynamic, physiological characteristics, and metabolic profiles of cyanobacteria, which results in their great adaptation ability to survive in diverse ecosystems. The evolution of these primitive bacteria resulted from the unique settings of photosynthetic machineries and the production of bioactive compounds. Specifically, bioactive compounds play roles as regulators to provide protection against extrinsic factors and act as intracellular signaling molecules to promote colonization. In addition to the roles of bioactive metabolites as indole alkaloids, terpenoids, mycosporine-like amino acids, non-ribosomal peptides, polyketides, ribosomal peptides, phenolic acid, flavonoids, vitamins, and antimetabolites for cyanobacterial survival in numerous habitats, which is the focus of this review, the bioactivities of these compounds for the treatment of various diseases are also discussed.

Protective effects of mycosporine-like amino acid-containing emulsions on UV-treated mouse ear tissue from the viewpoints of antioxidation and antiglycation

Mycosporine-like amino acids (MAAs) are promising natural antioxidative compounds with cosmetic applications for the prevention of skin aging. In this study, we evaluated the protective effects of natural resources-derived MAA-containing emulsions on mouse ear tissue exposed to UV irradiation. DBA/2CrSlc male mice were irradiated by UV light at 120 mJ/cm²/day for 9 days. MAA-containing emulsions were prepared using mycosporine-2-glycine (M2G), shinorine (SHI), or porphyra-334 (P334) and applied to mice ears at a dose of 50 mg/ear/day. After that, collected ear skin tissues were subjected to the observation of melanocytes, investigation for antioxidative stress markers, and measurement of advanced glycation-end products (AGEs). In addition, the antiglycative effects of MAAs were investigated in vitro. MAA-containing emulsions prepared in this study upregulated the activities of total superoxide dismutase (SOD) and catalase (CAT) in mouse ear tissue exposed to UV irradiation. Increased accumulation of copper/zinc (Cu/Zn) -SOD and/or CAT was also found in mouse ear tissue on which M2G- or P334-containing emulsion had been applied. Furthermore, P334 exhibited an antiglycative effect on elastin in vitro. Although MAA-containing emulsions have antioxidative effects as well as in vitro antiglycation, a protective effect by the accumulation of AGEs in mice ears exposed to UV was not observed. Thus, application of MAA-containing emulsions stimulated or protected the expression of antioxidant-associated proteins, thereby leading to upregulation of antioxidative activities in mouse ear skin samples tissues under UV irradiation. Additional optimization of MAA-containing emulsions, including composition, process, and dosage should be considered for further improvement of efficacy.

Development of a hybrid cell for energy production

This study focuses on the development of a new hybrid biological material to be applied in the production of electrical energy. These organo-metallic cells are constituted by cyanobacteria (Fischerella muscicola) and silver nanoparticles (AgNPs). AgNPs were obtained by green synthesis using the extract of the fruit of theBerberis halliiplant as reducing agent with two different concentrations of silver nitrate (AgNO₃), 1 and 10 mM. The morphology, physicochemical and electrical properties of the cyanobacteria with and without AgNPs were evaluated. To verify the efficacy of this new material, and the effect of the medium used, Nitrofoska or BG-11, the growth kinetics was evaluated by UV-vis up tot= 63 d with and without renewal of the culture medium and O₂/CO₂exchange. Through morphological characterizations ofFischerella muscicolait was possible to identify the presence of an associated bacterium identified using molecular techniques asPseudomona guguanensithat could act as a supporting organism in the growth of this cyanobacteria. The studies carried out did not shown cell toxicity for the cultures that have AgNPs and on the other hand, it was observed that the hybrid cells (Cy-AgNPs) are electron carriers recording an increase of up to 57% and 18% in their electrical potential with BG-11 and Nitrofoska culture media, respectively and an increase in the anodic current peak of 6.5% of Cy-AgNPs respect to onlyF. musicola.

Multi-omics Comparative Analysis of Streptomyces Mutants Obtained by Iterative Atmosphere and Room-Temperature Plasma Mutagenesis

Sponges, the most primitive multicellular animals, contain a large number of unique microbial communities. Sponge-associated microorganisms, particularly actinomyces, have the potential to produce diverse active natural products. However, a large number of silent secondary metabolic gene clusters have failed to be revived under laboratory culture conditions. In this study, iterative atmospheric room-temperature plasma. (ARTP) mutagenesis coupled with multi-omics conjoint analysis was adopted to activate the inactive wild Streptomyces strain. The desirable exposure time employed in this study was 75 s to obtain the appropriate lethality rate (94%) and mutation positive rate (40.94%). After three iterations of ARTP mutagenesis, the proportion of mutants exhibiting antibacterial activities significantly increased by 75%. Transcriptome analysis further demonstrated that the differential gene expression levels of encoding type I lasso peptide aborycin had a significant upward trend in active mutants compared with wild-type strains, which was confirmed by LC-MS results with a relative molecular mass of 1082.43 ([M + 2H]²⁺ at m/z = 2164.86). Moreover, metabolome comparative analysis of the mutant and wild-type strains showed that four spectra or mass peaks presented obvious differences in terms of the total ion count or extracting ion current profiles with each peak corresponding to a specific compound exhibiting moderate antibacterial activity against Gram-positive indicators. Taken together, our data suggest that the ARTP treatment method coupled with multi-omics profiling analysis could be used to estimate the valid active molecules of metabolites from microbial crudes without requiring a time-consuming isolation process.

Antioxidative, Anti-Inflammatory, and Anti-Aging Properties of Mycosporine-Like Amino Acids: Molecular and Cellular Mechanisms in the Protection of Skin-Aging

Prolonged exposure to ultraviolet (UV) radiation causes photoaging of the skin and induces a number of disorders, including sunburn, fine and coarse wrinkles, and skin cancer risk. Therefore, the application of sunscreen has gained much attention to reduce the harmful effects of UV irradiation on our skin. Recently, there has been a growing demand for the replacement of chemical sunscreens with natural UV-absorbing compounds. Mycosporine-like amino acids (MAAs), promising alternative natural UV-absorbing compounds, are a group of widely distributed, low molecular-weight, water-soluble molecules that can absorb UV radiation and disperse the absorbed energy as heat, without generating reactive oxygen species (ROS). More than 30 MAAs have been characterized, from a variety of organisms. In addition to their UV-absorbing properties, there is substantial evidence that MAAs have the potential to protect against skin aging, including antioxidative activity, anti-inflammatory activity, inhibition of protein-glycation, and inhibition of collagenase activity. This review will provide an overview of MAAs, as potential anti-aging ingredients, beginning with their structure, before moving on to discuss the most recent experimental observations, including the molecular and cellular mechanisms through which MAAs might protect the skin. In particular, we focus on the potential anti-aging activity of mycosporine-2-glycine (M2G).

UV Photoprotection, Cytotoxicity and Immunology Capacity of Red Algae Extracts

This study was designed to evaluate the potential use of algal extracts in cosmeceuticals, including factors related to biosecurity. The aqueous crude extracts of Hydropuntia cornea and Gracilariopsis longissima showed a good photoprotective capacity (Sun Protection Factor, SPF) due to, among other reasons, the presence of five types of mycosporine-like amino acids (MAAs) detected by high pressure liquid chromatography-photodiode array detector (HPLC-PDA) and electrospray ionization mass spectrometry (ESI-MS) (Palythine, Asterina-330, Shinorine, Porphyra-334, and Palythinol). The toxicity of the extracts was evaluated by the MTT assay, which is based on the metabolic reduction of MTT [3-(4,5-dimethylthiazol-2yl)-diphenyl tetrazolium bromide] by the action of the mitochondrial enzyme succinate dehydrogenase. This assay was carried out in vitro in three cell lines: one related to the immune system (murine macrophages of the immune system: RAW264.7) and two human cell lines related to the skin (gingival fibroblasts: HGF, and immortalized human keratinocytes: HaCaT). Both extracts showed no cytotoxic activity in both types of human cells, whereas they showed cytotoxicity in murine tumor cells of the immune system (macrophages: RAW264.7). On the other hand, the immunological activity in the murine macrophage RAW264.7 was studied at a concentration lower than 100 μg mL^-1 and lower than the EC₅₀, and evaluated by the production of pro-inflammatory compounds through an immunosorbent assay linked to enzymes such as tumor necrosis factor-α (TNF-α) or anti-inflammatory/proinflammatory enzymes such as interleukin-6 (IL-6). Both algae extracts induced the biosynthesis of TNF-α and IL-6. The production of TNF-α was much higher than that observed in the control (at a concentration of the aqueous extract higher than 5 μg mL^-1). These results support the theory that the extracts of H. cornea and G. longissima actively induce the production of cytokines. In summary, the extracts of these species did not show cytotoxicity in human cells, and they present with immunomodulatory and photoprotection capacity.