The Experts below are selected from a list of 846 Experts worldwide ranked by ideXlab platform
Richard W Castenholz - One of the best experts on this subject based on the ideXlab platform.
-
effects of nitrogen source on the synthesis of the uv screening compound Scytonemin in the cyanobacterium nostoc punctiforme pcc 73102
FEMS Microbiology Ecology, 2008Co-Authors: Erich D Fleming, Richard W CastenholzAbstract:The effects of nitrogen source (N2, NO3− and NH4+) on Scytonemin synthesis were investigated in the heterocystous cyanobacterium Nostoc punctiforme PCC 73102. With the required UVA radiation included, Nostoc synthesized three to seven times more Scytonemin while fixing nitrogen than when utilizing nitrate or ammonium. A similar increase in Scytonemin synthesis occurred when nitrate or ammonium became depleted by growth and Nostoc switched to diazotrophic metabolism with the differentiation of heterocysts. In addition, UVA-exposed cultures grown in medium with both NO3− and NH4+ synthesized some Scytonemin but synthesis increased when NH4+ was depleted and growth had become dependent on NO3− reduction. Although the mechanism is unclear, these results suggest that the greater the restriction in nitrogen accessibility, the greater the production of Scytonemin. Perhaps the entire response may be an interaction between this restriction and a resultant sensitivity to UV radiation that acts as a cue for determining the level of Scytonemin synthesis. Scytonemin is a stable UVR screening compound and appears to be synthesized by cyanobacteria as a long-term solution for reducing UVR exposure and damage, but mainly or solely, when metabolic activity is absent. It is likely that during metabolic resurgence, the presence of a dense Scytonemin sheath would facilitate the recovery process without the need for active defenses against UV radiation.
-
effects of periodic desiccation on the synthesis of the uv screening compound Scytonemin in cyanobacteria
Environmental Microbiology, 2007Co-Authors: Erich D Fleming, Richard W CastenholzAbstract:Summary Scytonemin is an ultraviolet radiation (UVR)-screening compound synthesized by some sheathed cyanobacteria exposed to high solar and sky radiation. It is primarily produced in response to UVA radiation, but certain environmental stresses can enhance synthesis. This study focuses on the effects of periodic desiccation on Scytonemin synthesis in three desiccation-tolerant cyanobacterial strains, Nostoc punctiforme PCC 73102, Chroococcidiopsis CCMEE 5056 and Chroococcidiopsis CCMEE 246. Nostoc punctiforme and Chroococcidiopsis CCMEE 5056 exposed to UVA radiation produced more concentrated Scytonemin screens when experiencing periodic desiccation (i.e. 1 day desiccated for every 2 days hydrated) than when continuously hydrated. A more concentrated Scytonemin screen would reduce the amount of UVR damage accrued when cells are desiccated and metabolically inactive. This might allow the cyanobacteria to allocate more energy to systems other than UVR damage repair during rehydration, which would facilitate recovery. The Scytonemin screen is extremely stable, remaining largely intact in the sheaths of desiccated N. punctiforme even when continuously exposed to UVA radiation for about 2 months. In contrast to the above findings, Scytonemin synthesis in Chroococcidiopsis CCMEE 246, a strain that produces Scytonemin constitutively under low visible light (no UVA), was partially inhibited by periodic desiccation.
-
the synthesis of the uv screening pigment Scytonemin and photosynthetic performance in isolates from closely related natural populations of cyanobacteria calothrix sp
Environmental Microbiology, 2003Co-Authors: Jesse G. Dillon, Richard W CastenholzAbstract:Summary Two populations of the cyanobacterium Calothrix sp. found in Yellowstone thermal spring outflows differ greatly in their contents of Scytonemin, a UV-screen- ing pigment, and in their photosynthetic carbon assimilation rates. Clonal isolates from both popula- tions were used to investigate these phenotypic dif- ferences. Identical partial 16S rDNA sequences ( ~ 900 bp) suggest a very close relationship between the two Calothrix populations and indicate that envi- ronmental differences may, in part, explain the field observations. The effects of native spring water on Scytonemin synthesis and photosynthesis were tested during experiments using plated cells. Results show differences in the spring water environment were at least partly responsible for the differences in Scytonemin content observed in the field. Further- more, spring water effects on photosynthetic perfor- mance suggest adaptation in these strains to their spring of origin. Controlled experiments performed using cultures grown in artificial liquid medium showed no significant difference in photosynthetic carbon uptake between strains. However, significant differences were detected in their ability to synthesize Scytonemin indicating genetic differences between populations. These findings suggest that both genetic and environmental differences are responsible for the naturally occurring variation in Scytonemin content and photosynthetic ability in these two closely related populations.
-
UV-acclimation responses in natural populations of cyanobacteria (Calothrix sp.).
Environmental Microbiology, 2003Co-Authors: Jesse G. Dillon, Scott R. Miller, Richard W CastenholzAbstract:Summary Phenotypic acclimation to changing conditions is typically thought to be beneficial to organisms in the environment. UV radiation is an important parameter affecting photosynthetic organisms in natural environments. We measured the response of photosynthetic carbon fixation in populations of cyanobacteria inhabiting a hot spring following acclimation to different UV treatments. These two very closely related populations of cyanobacteria, differing in their content of the extracellular UV-screening pigment Scytonemin, were acclimated in situ under natural solar irradiance modified by filters that excluded both UVA/B, only UVB or transmitted both UVA/B. Cells from each preacclimation treatment were subsequently assayed for photosynthetic performance under all UV conditions (incubation treatment) giving a two-factor experimental design for each population. No acclimation filter treatment effects were observed even after two months under different acclimation treatments. This suggests that UV photoacclimation does not occur in either of these populations, regardless of the presence of Scytonemin. By contrast, cells showed significant UV-inhibition during 1 h incubations under full sun. The population with high levels of Scytonemin usually had lower rates of photosynthetic carbon fixation than the Scytonemin-lacking population. However, the degree of UV inhibition, especially UVA inhibition, was higher for the cells without Scytonemin pigment. These results suggest that closely related natural cyanobacterial populations respond differently to natural irradiance conditions and may be adopting different strategies of UV tolerance.
-
Effect of environmental factors on the synthesis of Scytonemin, a UV-screening pigment, in a cyanobacterium (Chroococcidiopsis sp.)
Archives of Microbiology, 2002Co-Authors: Jesse G. Dillon, Cecelia M. Tatsumi, Patrick G. Tandingan, Richard W CastenholzAbstract:The UV-screening pigment Scytonemin is found in many species of ensheathed cyanobacteria. Past work has shown that the pigment is synthesized in response to exposure to UV-A irradiance. This study investigated the effect of other correlated stress factors including heat, osmotic and oxidative stress on the synthesis of Scytonemin in a clonal cyanobacterial isolate ( Chroococcidiopsis sp.) from an epilithic desert crust. Stress experiments were carried out both in conjunction with UV-A irradiance and in isolation. Increases in both temperature and photooxidative conditions in conjunction with UV-A caused a synergistic increase in the rate of Scytonemin production. In contrast, increased salt concentration under UV-A irradiance inhibited Scytonemin synthesis. However, unlike the responses to temperature and oxidative stress, cells synthesized low levels of Scytonemin under osmotic stress in the absence of Scytonemin-inducing irradiance. These results suggest that Scytonemin induction may be regulated as a part of a complex stress response pathway in which multiple environmental signals affect its synthesis.
Ferran Garciapichel - One of the best experts on this subject based on the ideXlab platform.
-
the widely conserved ebo cluster is involved in precursor transport to the periplasm during Scytonemin synthesis in nostoc punctiforme
Mbio, 2018Co-Authors: Kevin Klicki, Daniela Ferreira, Demetra Hamill, Blake Dirks, Natalie M Mitchell, Ferran GarciapichelAbstract:ABSTRACT Scytonemin is a dimeric indole-phenol sunscreen synthesized by some cyanobacteria under conditions of exposure to UVA radiation. While its biosynthetic pathway has been elucidated only partially, comparative genomics reveals that the Scytonemin operon often contains a cluster of five highly conserved genes (ebo cluster) of unknown function that is widespread and conserved among several bacterial and algal phyla. We sought to elucidate the function of the ebo cluster in the cyanobacterium Nostoc punctiforme by constructing and analyzing in-frame deletion mutants (one for each ebo gene and one for the entire cluster). Under conditions of UVA induction, all ebo mutants were Scytoneminless, and all accumulated a single compound, the Scytonemin monomer, clearly implicating all ebo genes in Scytonemin production. We showed that the Scytonemin monomer also accumulated in an induced deletion mutant of scyE, a non-ebo Scytonemin gene whose product is demonstrably targeted to the periplasm. Confocal autofluorescence microscopy revealed that the accumulation was confined to the cytoplasm in all ebo mutants but that that was not the case in the scyE deletion, with an intact ebo cluster, where the Scytonemin monomer was also excreted to the periplasm. The results implicate the ebo cluster in the export of the Scytonemin monomer to the periplasm for final oxidative dimerization by ScyE. By extension, the ebo gene cluster may play similar roles in metabolite translocation across many bacterial phyla. We discuss potential mechanisms for such a role on the basis of structural and phylogenetic considerations of the ebo proteins. IMPORTANCE Elucidating the biochemical and genetic basis of Scytonemin constitutes an interesting challenge because of its unique structure and the unusual fact that it is partially synthesized in the periplasmic space. Our work points to the ebo gene cluster, associated with the Scytonemin operon of cyanobacteria, as being responsible for the excretion of Scytonemin intermediates from the cytoplasm into the periplasm during biosynthesis. Few conserved systems have been described that facilitate the membrane translocation of small molecules. Because the ebo cluster is well conserved among a large diversity of bacteria and algae and yet insights into its potential function are lacking, our findings suggest that translocation of small molecules across the plasma membrane may be its generic role across microbes.
-
mutational studies of putative biosynthetic genes for the cyanobacterial sunscreen Scytonemin in nostoc punctiforme atcc 29133
Frontiers in Microbiology, 2016Co-Authors: Daniela Ferreira, Ferran GarciapichelAbstract:The heterocyclic indole-alkaloid Scytonemin is a sunscreen found exclusively among cyanobacteria. An 18-gene cluster is responsible for Scytonemin production in Nostoc punctiforme ATCC 29133. The upstream genes scyABCDEF in the cluster are proposed to be responsible for Scytonemin biosynthesis from aromatic amino acid substrates. In vitro studies of ScyA, ScyB and ScyC proved that these enzymes indeed catalyze initial pathway reactions. Here we characterize the role of ScyD, ScyE and ScyF, which were logically predicted to be responsible for late biosynthetic steps, in the biological context of N. punctiforme. In-frame deletion mutants of each were constructed (∆scyD, ∆scyE and ∆scyF) and their phenotypes studied. Expectedly, ∆scyE presents a Scytoneminless phenotype, but no accumulation of the predicted intermediaries. Surprisingly, ∆scyD retains Scytonemin production, implying that it is not required for biosynthesis. Indeed, scyD presents an interesting evolutionary paradox: it likely originated in a duplication event from scyE, and unlike other genes in the operon, it has not been subjected to purifying selection. This would suggest that it is a pseudogene, and yet scyD is highly conserved in the Scytonemin operon of cyanobacteria. ∆scyF also retains Scytonemin production, albeit exhibiting a reduction of the production yield compared with the wild-type. This indicates that ScyF is not essential but may play an adjuvant role for Scytonemin synthesis. Altogether, our findings suggest that these downstream genes are not responsible, as expected, for the late steps of Scytonemin synthesis and we must look for those functions elsewhere. These findings are particularly important for biotechnological production of this sunscreen through heterologous expression of its genes in more tractable organisms.
-
bacteria increase arid land soil surface temperature through the production of sunscreens
Nature Communications, 2016Co-Authors: Estelle Couradeau, Ferran Garciapichel, Ulas Karaoz, Ulisses Nunes Da Rocha, Trent R Northen, Eoin L BrodieAbstract:Soil surface temperature, an important driver of terrestrial biogeochemical processes, depends strongly on soil albedo, which can be significantly modified by factors such as plant cover. In sparsely vegetated lands, the soil surface can be colonized by photosynthetic microbes that build biocrust communities. Here we use concurrent physical, biochemical and microbiological analyses to show that mature biocrusts can increase surface soil temperature by as much as 10 °C through the accumulation of large quantities of a secondary metabolite, the microbial sunscreen Scytonemin, produced by a group of late-successional cyanobacteria. Scytonemin accumulation decreases soil albedo significantly. Such localized warming has apparent and immediate consequences for the soil microbiome, inducing the replacement of thermosensitive bacterial species with more thermotolerant forms. These results reveal that not only vegetation but also microorganisms are a factor in modifying terrestrial albedo, potentially impacting biosphere feedbacks on past and future climate, and call for a direct assessment of such effects at larger scales.
-
retracted carotenoids mycosporine like amino acid compounds phycobiliproteins and Scytonemin in the genus scytonema cyanobacteria a chemosystematic study1
Journal of Phycology, 2011Co-Authors: Antonia D Asencio, Ferran Garciapichel, Lucien HoffmannAbstract:The following article from the Journal of Phycology, “Carotenoids, Mycosporine-Like Amino Acid Compounds, Phycobiliproteins, And Scytonemin In The Genus Scytonema (Cyanobacteria): A Chemosystematic Study,” submitted by Antonia D. Asencio, and published online on August 22, 2011 on Wiley Online Library (http://www.wileyonlinelibrary.com), has been retracted by agreement between the journal Editor, Robert Sheath, and Wiley Periodicals, Inc. The retraction has been agreed upon request by Ferran Garcia-Pichel, listed as co-author, but not having agreed to the submission or publication of the manuscript.
-
a comparative genomics approach to understanding the biosynthesis of the sunscreen Scytonemin in cyanobacteria
BMC Genomics, 2009Co-Authors: Kendra Palmer, Tanya Soule, Ruth M Potrafka, Valerie Stout, Ferran GarciapichelAbstract:Background: The extracellular sunscreen Scytonemin is the most common and widespread indolealkaloid among cyanobacteria. Previous research using the cyanobacterium Nostoc punctiforme ATCC 29133 revealed a unique 18-gene cluster (NpR1276 to NpR1259 in the N. punctiforme genome) involved in the biosynthesis of Scytonemin. We provide further genomic characterization of these genes in N. punctiforme and extend it to homologous regions in other cyanobacteria. Results: Six putative genes in the Scytonemin gene cluster (NpR1276 to NpR1271 in the N. punctiforme genome), with no previously known protein function and annotated in this study as scyA to scyF, are likely involved in the assembly of Scytonemin from central metabolites, based on genetic, biochemical, and sequence similarity evidence. Also in this cluster are redundant copies of genes encoding for aromatic amino acid biosynthetic enzymes. These can theoretically lead to tryptophan and the tyrosine precursor, p-hydroxyphenylpyruvate, (expected biosynthetic precursors of Scytonemin) from end products of the shikimic acid pathway. Redundant copies of the genes coding for the key regulatory and rate-limiting enzymes of the shikimic acid pathway are found there as well. We identified four other cyanobacterial strains containing orthologues of all of these genes, three of them by database searches (Lyngbya PCC 8106, Anabaena PCC 7120, and Nodularia CCY 9414) and one by targeted sequencing (Chlorogloeopsis sp. strain Cgs-089; CCMEE 5094). Genomic comparisons revealed that most Scytonemin-related genes were highly conserved among strains and that two additional conserved clusters, NpF5232 to NpF5236 and a putative two-component regulatory system (NpF1278 and NpF1277), are likely involved in Scytonemin biosynthesis and regulation, respectively, on the basis of conservation and location. Since many of the protein product sequences for the newly described genes, including ScyD, ScyE, and ScyF, have export signal domains, while others have putative transmembrane domains, it can be inferred that Scytonemin biosynthesis is compartmentalized within the cell. Basic structural monomer synthesis and initial condensation are most likely cytoplasmic, while later reactions are predicted to be periplasmic. Conclusion: We show that Scytonemin biosynthetic genes are highly conserved among evolutionarily diverse strains, likely include more genes than previously determined, and are predicted to involve compartmentalization of the biosynthetic pathway in the cell, an unusual trait for prokaryotes.
William H Gerwick - One of the best experts on this subject based on the ideXlab platform.
-
probing the in vivo biosynthesis of Scytonemin a cyanobacterial ultraviolet radiation sunscreen through small scale stable isotope incubation studies and maldi tof mass spectrometry
Bioorganic & Medicinal Chemistry, 2011Co-Authors: Carla S Jones, William H Gerwick, Eduardo Esquenazi, Pieter C DorresteinAbstract:Abstract Scytonemin is a dimeric indole phenolic pigment found in the sheaths of many cyanobacteria. This pigment absorbs UV radiation protecting subtending cyanobacterial cells from harmful effects. Based on Scytonemin’s unique chemical structure, the pathway to its biosynthesis is uncertain, thus motivating the current investigation. Herein, we report the incorporation of both tyrosine and tryptophan into Scytonemin, and provide in vivo data supporting the tryptophan origin of the ketone carbon involved in the condensation of the two biosynthetic precursors. This study also reports on the new use of a small-scale, MALDI-TOF mass spectrometry technique to monitor the incorporation of isotopically labeled tyrosine during Scytonemin biosynthesis.
-
organization evolution and expression analysis of the biosynthetic gene cluster for Scytonemin a cyanobacterial uv absorbing pigment
Applied and Environmental Microbiology, 2009Co-Authors: Carla M Sorrels, William H Gerwick, Philip ProteauAbstract:Cyanobacteria are photosynthetic prokaryotes capable of protecting themselves from UV radiation through the biosynthesis of UV-absorbing secondary metabolites, such as the mycosporines and Scytonemin. Scytonemin, a novel indolic-phenolic pigment, is found sequestered in the sheath, where it provides protection to the subtending cells during exposure to UV radiation. The biosynthesis of Scytonemin is encoded by a previously identified gene cluster that is present in six cyanobacterial species whose genomes are available. A comparison of these clusters reveals that two major cluster architectures exist which appear to have evolved through rearrangements of large sections, such as those genes responsible for aromatic amino acid biosynthesis and through the insertion of genes that potentially confer additional biosynthetic capabilities. Differential transcriptional expression analysis demonstrated that the entire gene cluster is transcribed in higher abundance after exposure to UV radiation. This analysis helps delineate the cluster boundaries and indicates that regulation of this cluster is controlled by the presence or absence of UV radiation. The findings from an evolutionary phylogenetic analysis combined with the fact that the Scytonemin gene cluster is distributed across several cyanobacterial lineages led to our proposal that the distribution of this gene cluster is best explained through an ancient evolutionary origin.
-
the identification and characterization of the marine natural product Scytonemin as a novel antiproliferative pharmacophore
Journal of Pharmacology and Experimental Therapeutics, 2002Co-Authors: Christopher S Stevenson, William H Gerwick, Elizabeth A Capper, Amy K Roshak, Brian L Marquez, Chris Eichman, Jeffrey R Jackson, Michael Mattern, Robert S Jacobs, Lisa A MarshallAbstract:Marine natural products provide a rich source of chemical diversity that can be used to design and develop new, potentially useful therapeutic agents. We report here that Scytonemin, a pigment isolated from cyanobacteria, is the first described small molecule inhibitor of human polo -like kinase, a serine/threonine kinase that plays an integral role in regulating the G2/M transition in the cell cycle. Scytonemin inhibited polo -like kinase 1 activity in a concentration-dependent manner with an IC50 of 2 μM against the recombinant enzyme. Biochemical analysis showed that Scytonemin reduced GST- polo -like kinase 1 activity in a time-independent fashion, suggesting reversibility, and with a mixed-competition mechanism with respect to ATP. Although Scytonemin was less potent against protein kinase A and Tie2, a tyrosine kinase, it did inhibit other cell cycle-regulatory kinases like Myt1, checkpoint kinase 1, cyclin-dependent kinase 1/cyclin B, and protein kinase Cβ2 with IC50 values similar to that seen for polo -like kinase 1. Consistent with these effects, Scytonemin effectively attenuated, without chemical toxicity, the growth factor- or mitogen-induced proliferation of three cell types commonly implicated in inflammatory hyperproliferation. Similarly, Scytonemin (up to 10 μM) was not cytotoxic to nonproliferating endotoxin-stimulated human monocytes. In addition, Jurkat T cells treated with Scytonemin were induced to undergo apoptosis in a non-cell cycle-dependent manner consistent with its activities on multiple kinases. Here we propose that Scytonemin's dimeric structure, unique among natural products, may be a valuable template for the development of more potent and selective kinase inhibitors used for the treatment of hyperproliferative disorders.
-
the structure of Scytonemin an ultraviolet sunscreen pigment from the sheaths of cyanobacteria
Cellular and Molecular Life Sciences, 1993Co-Authors: Ferran Garciapichel, P J Proteau, William H Gerwick, Richard W CastenholzAbstract:Despite knowledge of the existence of the pigment called Scytonemin for over 100 years, its structure has remained unsolved until now. This pigment, the first shown to be an effective, photo-stable ultraviolet shield in prokaryotes, is a novel dimeric molecule (molec. wt. 544) of indolic and phenolic subunits and is known only from the sheaths enclosing the cells of cyanobacteria. It is probable that Scytonemin is formed from a condensation of tryptophan-and phenylpropanoid-derived subunits. The linkage between these units is unique among natural products and this novel ring structure is here termed the ‘scytoneman skeleton’. Scytonemin absorbs strongly and broadly in the spectral region 325–425 nm (UV-A-violet-blue, with an in vivo maximum at 370 nm). However, there is also major absorption in the UV-C (λmax=250nm) and UV-B (280–320 nm). The pigment has been recently shown to provide significant protection to cyanobacteria against damage by ultraviolet radiation. The pigment occurs in all phylogenetic lines of sheathed cyanobacteria and possibly represents a UV screening strategy far more ancient than that of plant flavonoids and animal melanins. How diverse organisms deal with UV radiation is considered of vital importance to global ecology.
Howell G. M. Edwards - One of the best experts on this subject based on the ideXlab platform.
-
raman spectroscopic fingerprints of Scytonemin imine density functional theory calculations of a novel potential biomarker
Philosophical Transactions of the Royal Society A, 2014Co-Authors: Tereza Varnali, Howell G. M. EdwardsAbstract:Scytonemin-imine, a novel derivative of Scytonemin, has been isolated and identified very recently and proposed to serve as a photoprotective biomarker for certain bacteria growing under intense photon flux density. This study predicts theoretically the Raman spectrum of Scytonemin-imine by density functional theory calculations and provides comparison of major bands to those of Scytonemin, the parent compound for which both the experimentally characterized and theoretically predicted spectra exist in the literature. It is proposed to be an addendum to the collection of our previous work on scytonamin and its derivatives to facilitate recognition of the diagnostic Raman spectral signatures for Scytonemin-imine.
-
raman spectroscopic identification of Scytonemin and its derivatives as key biomarkers in stressed environments
Philosophical Transactions of the Royal Society A, 2014Co-Authors: Tereza Varnali, Howell G. M. EdwardsAbstract:Raman spectroscopy has been identified as an important first-pass analytical technique for deployment on planetary surfaces as part of a suite of instrumentation in projected remote space exploration missions to detect extant or extinct extraterrestrial life signatures. Aside from the demonstrable advantages of a non-destructive sampling procedure and an ability to record simultaneously the molecular signatures of biological, geobiological and geological components in admixture in the geological record, the interrogation and subsequent interpretation of spectroscopic data from these experiments will be critically dependent upon the recognition of key biomolecular markers indicative of life existing or having once existed in extreme habitats. A comparison made with the characteristic Raman spectral wavenumbers obtained from standards is not acceptable because of shifts that can occur in the presence of other biomolecules and their host mineral matrices. In this paper, we identify the major sources of difficulty experienced in the interpretation of spectroscopic data centring on a key family of biomarker molecules, namely Scytonemin and its derivatives; the parent Scytonemin has been characterized spectroscopically in cyanobacterial colonies inhabiting some of the most extreme terrestrial environments and, with the support of theoretical calculations, spectra have been predicted for the characterization of several of its derivatives which could occur in novel extraterrestrial environments. This work will form the foundation for the identification of novel biomarkers and for their Raman spectroscopic discrimination, an essential step in the interpretation of potentially complex and hitherto unknown biological radiation protectants based on the scytoneman and scytonin molecular skeletons which may exist in niche geological scenarios in the surface and subsurface of planets and their satellites in our Solar System.
-
Scytonin, a novel cyanobacterial photoprotective pigment: calculations of Raman spectroscopic biosignatures
Journal of Molecular Modeling, 2014Co-Authors: Tereza Varnali, Howell G. M. EdwardsAbstract:The Raman spectrum of scytonin, a novel derivative of the parent Scytonemin, is predicted from DFT calculations of the most stable, lowest energy, conformational structure. The diagnostic importance of this study relates to the spectral ability to discriminate between Scytonemin and its derivatives alone or in admixture with geological matrices from identified characteristic Raman spectral signatures. The successful interpretation of biosignatures from a wide range of cyanobacterial extremophilic colonization in terrestrial and extraterrestrial scenarios is a fundamental requirement of the evaluation of robotic spectroscopic instrumentation in search for life missions. Scytonemin is produced exclusively by cyanobacterial colonies in environmentally stressed habitats and is widely recognized as a key target biomarker molecule in this enterprise. Here, the detailed theoretical analysis of the structure of scytonin enables a protocol to be established for the recognition of characteristic bands in its Raman spectrum and to accomplish the successful differentiation between scytonin and Scytonemin as well as other Scytonemin derivatives such as the dimethoxy and tetramethoxy compounds that have been isolated from cyanobacterial colonies but which have not yet been characterized spectroscopically. The results of this study will facilitate an extension of the database capability for miniaturized Raman spectrometers which will be carried on board search for life robotic missions to Mars, Europa, and Titan.
-
reduced and oxidised Scytonemin theoretical protocol for raman spectroscopic identification of potential key biomolecules for astrobiology
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2014Co-Authors: Tereza Varnali, Howell G. M. EdwardsAbstract:Abstract Scytonemin is an important UV-radiation protective biomolecule synthesised by extremophilic cyanobacteria in stressed terrestrial environments. Scytonemin and its reduced form have been both isolated experimentally and the Raman spectrum for Scytonemin has been assigned and characterised experimentally both in extracts and in living extremophilic cyanobacterial colonies. Scytonemin is recognised as a key biomarker molecule for terrestrial organisms in stressed environments. We propose a new, theoretically plausible structure for oxidised Scytonemin which has not been mentioned in the literature hitherto. DFT calculations for Scytonemin, reduced Scytonemin and the new structure modelled and proposed for oxidised Scytonemin are reported along with their Raman spectroscopic data and λmax UV-absorption data obtained theoretically. Comparison of the vibrational spectroscopic assignments allows the three forms of Scytonemin to be detected and identified and assist not only in the clarification of the major features in the experimentally observed Raman spectral data for the parent Scytonemin but also support a protocol proposed for their analytical discrimination. The results of this study provide a basis for the search for molecules of this type in future astrobiological missions of exploration and the search for extinct and extant life terrestrially.
-
theoretical study of novel complexed structures for methoxy derivatives of Scytonemin potential biomarkers in iron rich stressed environments
Astrobiology, 2013Co-Authors: Tereza Varnali, Howell G. M. EdwardsAbstract:Abstract Scytonemin is a cyanobacterial sheath pigment with potent UV (UVA, UVB, and UVC) absorbing properties. Di- and tetramethoxy derivatives of Scytonemin have also been found and described in the literature. The importance of these biomolecules is their photoprotective function, which is one of the major survival strategies adopted by extremophiles in environmentally stressed conditions. Also, iron compounds [particularly iron(III) oxides] offer an additional UV-protecting facility to subsurface endolithic biological colonization; hence, banded iron formations (accompanied by zones of depletion of iron) in rock matrices have attracted attention with special interest in the method of transportation of iron compounds through the rock. Di- and tetramethoxyScytonemin and their iron(III) complexes have been modeled and studied computationally by using density functional theory calculations at the level of B3LYP/6-31G** methodology. We propose new structures that could feature in survival strategy and faci...
Rajeshwar P. Sinha - One of the best experts on this subject based on the ideXlab platform.
-
photoprotective role of uv screening pigment Scytonemin against uv b induced damages in the heterocyst forming cyanobacterium nostoc sp strain hkar 2
Brazilian Journal of Botany, 2020Co-Authors: Abha Pandey, Jainendra Pathak, Vidya Singh, Haseen Ahmed, Deepak K Singh, Deepak Kumar, Rajeshwar P. SinhaAbstract:Scytonemin acts as a natural photoprotectant against high-intensity solar photosynthetically active radiation and harmful ultraviolet radiation, which has been reported in several cyanobacteria, and gets accumulated in their extracellular polysaccharide sheath. UV-B radiation (280–315 nm) has detrimental effect on physiological and biochemical processes of living organisms. In this study, Scytonemin was extracted from dried cyanobacterial mats collected from the bark of mango trees and was partially characterized using high-performance liquid chromatography and electrospray ionization–mass spectrometry (retention time: 1.7 min; UVλmax: 386 nm; [M + H]+m/z: 545.1). Thereafter, photoprotective capabilities of Scytonemin against UV-B radiation in a non-sheathed cyanobacterium Nostoc sp. strain HKAR-2 were assessed followed by studying its role in the recovery process. We found that UV-B radiation inhibited growth, survival, Chl a content and total protein concentration and caused an increase in total carotenoid content. The activities of nitrogen-assimilating enzymes, glutamine synthetase and nitrate reductase, were also affected. In vivo nitrate reductase activity exhibited a stimulatory response, while in vivo glutamine synthetase activity was adversely inhibited after UV-B exposure. Scytonemin with different concentrations exhibited efficient photoprotective ability by nullifying the deleterious effects of UV-B and also enhanced the recovery process. UV-screening effects of Scytonemin in terms of growth, pigmentation, survival and nitrogen metabolism enzymes in the cyanobacterial strain have been reported for the first time in the present study. Our results suggest that Scytonemin aids in the better survival and adaptability of cyanobacteria in stressed habitats facing harsh environmental conditions.
-
Cyanobacterial Secondary Metabolite Scytonemin: A Potential Photoprotective and Pharmaceutical Compound
Proceedings of the National Academy of Sciences India Section B: Biological Sciences, 2019Co-Authors: Jainendra Pathak, Rajeshwar P. Sinha, Abha Pandey, Pankaj K. Maurya, Rajneesh Rajneesh, Shailendra P. SinghAbstract:Scytonemin is a lipid-soluble, highly stable, yellow–brown-coloured secondary metabolite that is accumulated in the extracellular polysaccharide sheath of several but not all members of cyanobacteria. Chemically, Scytonemin is an indole alkaloid composed of two heterocyclic units symmetrically connected through a carbon–carbon bond. Thus, Scytonemin is unique among natural products due to its special structure, location in a cell, as well as strong absorption maxima in UV-A in addition to the violet–blue region. Traditionally, Scytonemin is a well-established photoprotective compound against ultraviolet radiation. Its accumulation in the cyanobacterial sheath has been suggested to be a strategy adopted by several cyanobacteria to protect their cellular components against damaging effects of UVR. Additionally, recent studies have also established the importance of Scytonemin in reactive oxygen species scavenging as well as in controlling the growth of cancerous cells. Thus, Scytonemin is both ecologically as well as pharmaceutically important metabolite. Recent developments made in the biochemistry and genetics of this compound have paved the way for its application and commercialization for human welfare. This review aims to present a brief history of the compound with chronological developments made in the study of Scytonemin and emphasizes its physiochemistry, analytical chemistry, biochemistry, and genetics. We provide a separate section for metabolic engineering and potential applications of Scytonemin, mainly as sunscreen and anti-cancerous drugs. We also discuss the future research directions which need to be worked out.
-
genetic regulation of Scytonemin and mycosporine like amino acids maas biosynthesis in cyanobacteria
Plant Gene, 2019Co-Authors: Jainendra Pathak, Shailendra P. Singh, Haseen Ahmed, Donatp Hader, Rajeshwar P. SinhaAbstract:Abstract Scytonemin and mycosporine-like amino acids (MAAs) are important novel secondary metabolites synthesized by cyanobacteria to protect themselves from lethal ultraviolet (UV) radiation. Scytonemin, the extracellular polysaccharide sheath pigment is found in several cyanobacterial species and is a lipid-soluble dimeric pigment consisting of phenolic and indolic subunits linked through an olefinic carbon atom. Structure of MAAs consists of aminocyclohexenone or an aminocyclohexinimine chrompohore conjugated with the nitrogen substituent of an amino acid or its amino alcohol. MAAs are small, colorless water soluble compounds. These UV screening compounds are highly photostable photoprotectant and also serve as potent antioxidants. Multiple environmental signals influence Scytonemin and MAAs synthesis and regulation of induction of these UV screening compounds is a part of complex stress response pathway. Hence, proper understanding of genetic regulation and biosynthesis of these microbial sunscreens would not only provide scientific insight in a major class of secondary metabolites but will also help in commercial production of these new age ecofriendly sunscreens.
-
screening and partial purification of photoprotective pigment Scytonemin from cyanobacterial crusts dwelling on the historical monuments in and around varanasi india
Microbiological Research, 2017Co-Authors: Jainendra Pathak, Arun S Sonker, R Richa, R Rajneesh, Vinod K Kannaujiya, Vidya Singh, Haseen Ahmed, Rajeshwar P. SinhaAbstract:In the present investigation, biological crusts from the surface of eight historical monuments of Varanasi, India, were examined for the presence of Scytonemin (a cyanobacterial photoprotective pigment) containing cyanobacterial species. Lyngbya sp. and Scytonema sp. were the dominant cyanobacteria present in all crust samples. The absorption spectroscopic data of chlorophyll, carotenoids and Scytonemin showed that Scytonemin was more abundant than the carotene and chlorophyll in all the crusts. Identification of these compounds was done using UV-Vis spectroscopy and High Performance Liquid Chromatography (HPLC) analysis. HPLC analysis revealed the presence of Scytonemin in seven out of eight samples and peaks of Scytonemin with retention time ranging from 1.4-1.9 min with corresponding absorbance maxima at 386, 300 and 252±2 nm. As per our knowledge this is the first report of its kind from monuments of Varanasi. From this study, it can be concluded that synthesis of photoprotective compounds like Scytonemin and its derivatives counteract the damaging effects of solar radiation which enable cyanobacteria to colonize and inhabit almost all kinds of habitats, including extreme lithic habitats, such as rocks and walls of monuments which face prolonged high intensity solar radiation.
-
Nanobiotechnology of cyanobacterial UV-protective compounds: innovations and prospects
Food Preservation, 2016Co-Authors: Richa, Jainendra Pathak, Arun S Sonker, Vidya Singh, Rajeshwar P. SinhaAbstract:Abstract Cyanobacteria synthesize novel secondary UV-protective metabolites such as mycosporine-like amino acids (MAAs) and Scytonemin. MAAs are composed of aminocyclohexenone or an aminocyclohexinimine chromophore conjugated with the nitrogen substituent of an amino acid or its amino alcohol and are small, water soluble, and colorless compounds. The extracellular polysaccharide sheath pigment Scytonemin found in some cyanobacteria is a lipid-soluble dimeric pigment composed of indolic and phenolic subunits linked by an olefinic carbon atom. These compounds are highly photostable and act as potent photoprotectant and antioxidant. Inorganic nanoconjugates of these biomolecules could serve as a strong nontoxic, ecofriendly, biological sunscreen agent as they prolong their residence time in the target samples. Hence, future research must be focused on the investigation of facile, efficient, environmentally benign synthesis and use of these nanoparticle–biomolecule complexes in cosmetic and pharmaceutical industries as well as food industry to improve the shelf life of commodities.
