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LIGHT DEPENDENT CHANGES IN PEROXIDASE ACTIVITY AND PEROXIDE HYDROGEN GENERATION IN THE WHEAT SEEDLINGS  [PDF]
Tomilin M.V.,Olyunina L.N.,Veselov A.P.
Journal of Stress Physiology & Biochemistry , 2011,
Abstract: Participation of light in modification of peroxidase enzymatic system activity and peroxide hydrogen generation in the wheat seedlings shoot and root endocellular compartment is revealed. It is shown that in elevated parts of seedlings light activates oxidase peroxidase function and causes peroxide hydrogen accumulation (oxidative burst); in roots – light induces equivalent changes of both enzymatic functions, without causing change of ROS level.
Genes Associated with 2-Methylisoborneol Biosynthesis in Cyanobacteria: Isolation, Characterization, and Expression in Response to Light  [PDF]
Zhongjie Wang,Yao Xu,Jihai Shao,Jie Wang,Renhui Li
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0018665
Abstract: The volatile microbial metabolite 2-methylisoborneol (2-MIB) is a root cause of taste and odor issues in freshwater. Although current evidence suggests that 2-MIB is not toxic, this compound degrades water quality and presents problems for water treatment. To address these issues, cyanobacteria and actinomycetes, the major producers of 2-MIB, have been investigated extensively. In this study, two 2-MIB producing strains, coded as Pseudanabaena sp. and Planktothricoids raciborskii, were used in order to elucidate the genetic background, light regulation, and biochemical mechanisms of 2-MIB biosynthesis in cyanobacteria. Genome walking and PCR methods revealed that two adjacent genes, SAM-dependent methyltransferanse gene and monoterpene cyclase gene, are responsible for GPP methylation and subsequent cyclization to 2-MIB in cyanobacteria. These two genes are located in between two homologous cyclic nucleotide-binding protein genes that may be members of the Crp-Fnr regulator family. Together, this sequence of genes forms a putative operon. The synthesis of 2-MIB is similar in cyanobacteria and actinomycetes. Comparison of the gene arrangement and functional sites between cyanobacteria and other organisms revealed that gene recombination and gene transfer probably occurred during the evolution of 2-MIB-associated genes. All the microorganisms examined have a common origin of 2-MIB biosynthesis capacity, but cyanobacteria represent a unique evolutionary lineage. Gene expression analysis suggested that light is a crucial, but not the only, active regulatory factor for the transcription of 2-MIB synthesis genes. This light-regulated process is immediate and transient. This study is the first to identify the genetic background and evolution of 2-MIB biosynthesis in cyanobacteria, thus enhancing current knowledge on 2-MIB contamination of freshwater.
The regulation of light sensing and light harvesting impacts the use of cyanobacteria as biotechnology platforms  [PDF]
Beronda L. Montgomery
Frontiers in Bioengineering and Biotechnology , 2014, DOI: 10.3389/fbioe.2014.00022
Abstract: Light is harvested in cyanobacteria by chlorophyll-containing photosystems embedded in the thylakoid membranes and phycobilisomes (PBSs), photosystem-associated light-harvesting antennae. Light absorbed by the PBSs and photosystems can be converted to chemical energy through photosynthesis. Photosynthetically-fixed carbon pools, which are constrained by photosynthetic light capture versus the dissipation of excess light absorbed, determine the available organismal energy budget. The molecular bases of the environmental regulation of photosynthesis, photoprotection and photomorphogenesis are still being elucidated in cyanobacteria. Thus, the potential impacts of these phenomena on the efficacy of developing cyanobacteria as robust biotechnological platforms require additional attention. Current advances and persisting needs for developing cyanobacterial production platforms that are related to light sensing and harvesting include the development of tools to balance the utilization of absorbed photons for conversion to chemical energy and biomass versus light dissipation in photoprotective mechanisms. Such tools can be used to direct energy to more effectively support the production of desired bioproducts from sunlight.
PACAP-Deficient Mice Exhibit Light Parameter–Dependent Abnormalities on Nonvisual Photoreception and Early Activity Onset  [PDF]
Chihiro Kawaguchi,Yasushi Isojima,Norihito Shintani,Michiyoshi Hatanaka,Xiaohong Guo,Nobuaki Okumura,Katsuya Nagai,Hitoshi Hashimoto,Akemichi Baba
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0009286
Abstract: The photopigment melanopsin has been suggested to act as a dominant photoreceptor in nonvisual photoreception including resetting of the circadian clock (entrainment), direct tuning or masking of vital status (activity, sleep/wake cycles, etc.), and the pupillary light reflex (PLR). Pituitary adenylate cyclase-activating polypeptide (PACAP) is exclusively coexpressed with melanopsin in a small subset of retinal ganglion cells and is predicted to be involved extensively in these responses; however, there were inconsistencies in the previous reports, and its functional role has not been well understood.
Short-Term Regulation of Murine Colonic NBCe1-B (Electrogenic Na+/HCO3? Cotransporter) Membrane Expression and Activity by Protein Kinase C  [PDF]
Oliver May, Haoyang Yu, Brigitte Riederer, Michael P. Manns, Ursula Seidler, Oliver Bachmann
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0092275
Abstract: The colonic mucosa actively secretes HCO3?, and several lines of evidence point to an important role of Na+/HCO3? cotransport (NBC) as a basolateral HCO3? import pathway. We could recently demonstrate that the predominant NBC isoform in murine colonic crypts is electrogenic NBCe1-B, and that secretagogues cause NBCe1 exocytosis, which likely represents a component of NBC activation. Since protein kinase C (PKC) plays a key role in the regulation of ion transport by trafficking events, we asked whether it is also involved in the observed NBC activity increase. Crypts were isolated from murine proximal colon to assess PKC activation as well as NBC function and membrane abundance using fluorometric pHi measurements and cell surface biotinylation, respectively. PKC isoform translocation and phosphorylation occurred in response to PMA-, as well as secretagogue stimulation. The conventional and novel PKC inhibitors G?6976 or G?6850 did not alter NBC function or surface expression by themselves, but stimulation with forskolin (10?5 M) or carbachol (10?4 M) in their presence led to a significant decrease in NBC-mediated proton flux, and biotinylated NBCe1. Our data thus indicate that secretagogues lead to PKC translocation and phosphorylation in murine colonic crypts, and that PKC is necessary for the increase in NBC transport rate and membrane abundance caused by cholinergic and cAMP-dependent stimuli.
Electron transport and light-harvesting switches in cyanobacteria  [PDF]
Conrad W. Mullineaux
Frontiers in Plant Science , 2014, DOI: 10.3389/fpls.2014.00007
Abstract: Cyanobacteria possess multiple mechanisms for regulating the pathways of photosynthetic and respiratory electron transport. Electron transport may be regulated indirectly by controlling the transfer of excitation energy from the light-harvesting complexes, or it may be more directly regulated by controlling the stoichiometry, localisation and interactions of photosynthetic and respiratory electron transport complexes. Regulation of the extent of linear vs. cyclic electron transport is particularly important for controlling the redox balance of the cell. This review discusses what is known of the regulatory mechanisms and the timescales on which they occur, with particular regard to the structural reorganisation needed and the constraints imposed by the limited mobility of membrane-integral proteins in the crowded thylakoid membrane. Switching mechanisms requiring substantial movement of integral thylakoid membrane proteins occur on slower timescales than those that require the movement only of cytoplasmic or extrinsic membrane proteins. This difference is probably due to the restricted diffusion of membrane-integral proteins. Multiple switching mechanisms may be needed to regulate electron transport on different timescales.
TonB-dependent transporters and their occurrence in cyanobacteria
Oliver Mirus, Sascha Strauss, Kerstin Nicolaisen, Arndt von Haeseler, Enrico Schleiff
BMC Biology , 2009, DOI: 10.1186/1741-7007-7-68
Abstract: We have screened all publicly available eubacterial genomes for sequences representing (putative) TBDTs. Based on sequence similarity, we identified 195 clusters, where elements of one cluster may possibly recognize similar substrates. For Anabaena sp. PCC 7120 we identified 22 genes as putative TBDTs covering almost all known TBDT subclasses. This is a high number of TBDTs compared to other cyanobacteria. The expression of the 22 putative TBDTs individually depends on the presence of iron, copper or nitrogen.We exemplified on TBDTs the power of CLANS-based classification, which demonstrates its importance for future application in systems biology. In addition, the tentative substrate assignment based on characterized proteins will stimulate the research of TBDTs in different species. For cyanobacteria, the atypical dependence of TBDT gene expression on different nutrition points to a yet unknown regulatory mechanism. In addition, we were able to clarify a hypothesis of the absence of TonB in cyanobacteria by the identification of according sequences.Filamentous cyanobacteria contain molecular machines for oxygenic photosynthesis under all growth conditions [1]. These machines, as well as those involved in respiration and nitrogen metabolism, depend on non-proteinaceous cofactors such as iron [2,3]. The level of iron found in cyanobacteria is generally one order of magnitude higher than in non-photosynthetic bacteria [4] and represents about 0.1% of their biomass [5]. Even though iron and copper are required for the function of respiratory and photosynthetic complexes, their intracellular level has to be tightly controlled as these ions pose a risk of oxidation [3]. Therefore, the uptake of iron is highly regulated in order to avoid intoxication. On the other hand, it is hypothesized that iron limitation might have been one of the selective forces in the evolution of cyanobacteria [6], and one might speculate that those cyanobacteria with the most efficient iron upt
Telomere Protective Effects of a Cyanobacteria Phycocyanin against Blue Light and UV Irradiations: A Skin Anti-Aging and Photo-Protective Agent  [PDF]
Francine Joly, Jean-Eric Branka, Eric Darnis, Luc Lefeuvre
Journal of Cosmetics, Dermatological Sciences and Applications (JCDSA) , 2019, DOI: 10.4236/jcdsa.2019.94031
Abstract: Background: Cyanobacteria phycocyanins (Cps) have already shown powerful antioxidant properties. In human cells submitted to oxidative stress the telomeres length decrease, the expression of progerin and the activity of mTOR are increased. At our knowledge, there is no published data on Cps correlated with ultraviolet radiation (UV) and blue light effects in human cells regarding telomeres’ length, progerin expression or mTOR1 complex activity. Objectives: In this study, we sought to assess 1) telomeres’ length in newborn human fibroblasts exposed to UV and blue light; 2) progerin production in mature human normal fibroblasts exposed to UV; 3) mTOR1 activation in adult human normal keratinocytes exposed to UV, analyzing the activity of a Cyanobacteria phycocyanin (Cp) in these in vitro models. Materials and Methods: Human skin fibroblasts or human normal keratinocytes were cultured—in the absence or in the presence of Cp and submitted to UVB + UVA and blue light irradiations. Telomeres’ length, progerin expression and mTOR1 activity were then assessed by molecular biology and immuno-enzymatic methods. Results: In cultured fibroblasts exposed to irradiations and treated by Cp, telomeres’ shortage and progerin expression were lower compared to irradiated untreated cells. In cultured keratinocytes treated by Cp and exposed to irradiations, the mTOR activity was lower compared to irradiated untreated cells. Conclusions: In these in vitro studies on human skin fibroblasts and on normal human keratinocytes, the cyanobacteria phycocyanin (Cp) showed a decrease of damages induced by UV and blue light expressed by telomeres preservation and downregulation of progerin expression and of mTOR activity, thus showing skin anti-aging and photo-protective potential.
Effects of Light Intensity on the Growth of Cyanobacteria Isolated from Huperzia. Serrata (Thunb.) Trevis in Liquid Medium
光照强度对蛇足石杉共生蓝藻细胞悬浮培养的影响

GUO Bin,ZHANG Xiang-da,WEI Ya-hui,
郭斌
,张向达,尉亚辉

光子学报 , 2012,
Abstract: The symbiotic cyanobacteria were isolated from the sporangium of Huperzia. Serrata (Thunb.) Trevis (H. Serrata). And the effects of light intensity on the growth of cyanobacteria were studied. The results showed that the optimal biomass of cyanobacteria cell was obtained under 500 Lx light intensity. The higher light intensity (> 2000 Lx) repressed the cyanobacteria cell growth which would be faded and turned white. During the growth of symbiotic cyanobacteria, the chlorophyll a content was significantly reduced with the light intensity increased, which were positively correlated with the biomass reduction under higher light intensity. In addition, we found that the biomass and the chlorophyll a content of symbiotic cyanobacteria were higher under green light or blue light than those under red light. In conclusion, the weak light was suitable for the growth of symbiotic cyanobacteria isolated from the sporangium of H. Serrata. And the optimal light quality on the growth of symbiotic cyanobacteria was green light or blue light.
Irreversible Collective Migration of Cyanobacteria in Eutrophic Conditions  [PDF]
Julien Dervaux,Annick Méjean,Philippe Brunet
Physics , 2015, DOI: 10.1371/journal.pone.0120906
Abstract: In response to natural or anthropocentric pollutions coupled to global climate changes, microorganisms from aquatic environments can suddenly accumulate on water surface. These dense suspensions, known as blooms, are harmful to ecosystems and significantly degrade the quality of water resources. In order to determine the physico-chemical parameters involved in their formation and quantitatively predict their appearance, we successfully reproduced irreversible cyanobacterial blooms in vitro. By combining chemical, biochemical and hydrodynamic evidences, we identify a mechanism, unrelated to the presence of internal gas vesicles, allowing the sudden collective upward migration in test tubes of several cyanobacterial strains (Microcystis aeruginosa PCC 7005, Microcystis aeruginosa PCC 7806 and Synechocystis sp. PCC 6803). The final state consists in a foamy layer of biomass at the air-liquid interface, in which micro-organisms remain alive for weeks, the medium lying below being almost completely depleted of cyanobacteria. These "laboratory blooms" start with the aggregation of cells at high ionic force in cyanobacterial strains that produce anionic extracellular polymeric substances (EPS). Under appropriate conditions of nutrients and light intensity, the high photosynthetic activity within cell clusters leads the dissolved oxygen (DO) to supersaturate and to nucleate into bubbles. Trapped within the EPS, these bubbles grow until their buoyancy pulls the biomass towards the free surface. By investigating a wide range of spatially homogeneous environmental conditions (illumination, salinity, cell and nutrient concentration) we identify species-dependent thresholds and timescales for bloom formation. We conclude on the relevance of such results for cyanobacterial bloom formation in the environment and we propose an efficient method for biomass harvesting in bioreactors.
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