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[en] Highlights: Excitation of the 15ZPg state of RcaE photoreceptor generates three primary photoproducts. Only the Lumi-Go, photoproduct propagates to generate the 15EPr state. Excitation of 15EPr generates the Lumi-Rf photoproduct with an anomalously long living lifetime. Cyanobacteriochrome RcaE regulates Type III complementary chromatic adaption in the cyanobacterium Fremyella diplosiphon by photoswitching between a green-absorbing dark state (15ZPg) and red-absorbing photoproduct (15EPr). Ultrafast photodynamics of RcaE involve tautomerization of the bilin chromophore, inhomogeneity, and the generation of three primary photointermediates in the forward reaction (Lumi-Go, Lumi-Gr, and Lumi-Gf). The secondary photodynamics reported here show that only Lumi-Go evolves to 15EPr via spectrally similar Meta-Go1 and Meta-Go2 intermediates, with a protonation reaction occurring at the final step on the millisecond timescale. Reverse reaction dynamics were characterized and reveal an unusually long-lived Lumi-Rf photoproduct and a blue-shifted Meta-Ry intermediate.
[en] In a unicellular cyanobacterium, the mobile fraction of phycobilisome (PBS) was found to be maximum at a particular redox value of QA (i.e., 0.52). An upward or downward shift in the redox value leads to a decrease in this mobile fraction of PBS. Furthermore, the regulatory effect of the redox state of QA on PBS mobility was found to be independent of the effect exerted by the plastoquinone pool. These findings indicate for the first time that PBS mobility is regulated by the QA redox state in cyanobacteria. A possible working mechanism underlying this control is discussed.
[en] The experiments were carried out to assess the effect of fertilizer application on indigenous medicinal plant Andrographis paniculata Nees (Sega-gyi) on yield components such as plant heigh (cm), fresh weight of whole plant (g), dry weigth of whole plant (g), dry weigth of leave per plant (g), mineral elemental contents of the leaves (N, P, K, Ca and Mg) and medically active compound andrographolide of the leaves from the green-house experiment. Various methods applied in the growth of medicinal plant A. paniculata Nees (Sega-gyi), comprised the dripping (Dropwise) and the spraying methods of the prepared blue green algae (BGA) Spirulina, the composite mixture of prepared BGA+ soil, mineral fertilizer + soil and soil itself as control. In all the fertilizer treatments, the dripping (Dropwise) method using the BGA biofertilizer gave rise to the highest growth of 100 cm when the average fresh weigth of the whole plant was 440g. Andrographolide crystals were isolated, identified and confirmed by chromatographic techniques. A single standard HPLC peak by UV detection (225 nm) indication a retention time of 4.36 min and its melting point (232 C) were found to correspond to the literature values. Analytical results of the leaves of Sega-gyi by the dripping (Dropwise) method indicated the presence of 2.12% andrographolide and also the mineral elements with the composition of N (22.78), P (1.93), K (16.15), Ca (23.70) and Mg (4.85) mg/g. Although the mechanism of micro-algal plant growth regulatory action has not yet been studied, from this research work it was observed that the BGA biofertilizer promotes plant growth, improves the soil physical conditions, and also enhance the yield of medicinally active compound andrographolide.
[en] Phytoplankton are key components of ecosystems. Their growth is deeply influenced by temperature. In a context of global change, it is important to precisely estimate the impact of temperature on these organisms at different spatial and temporal scales. Here, we review the existing deterministic models used to represent the effect of temperature on microbial growth that can be applied to phytoplankton. We first describe and provide a brief mathematical analysis of the models used in constant conditions to reproduce the thermal growth curve. We present the mechanistic assumptions concerning the effect of temperature on the cell growth and mortality, and discuss their limits. The coupling effect of temperature and other environmental factors such as light are then shown. Finally, we introduce the models taking into account the acclimation needed to thrive with temperature variations. The need for new thermal models, coupled with experimental validation, is argued.
[en] Microcystis aeruginosa, a species of freshwater cyanobacteria, is known to be one of the dominant species causing cyanobacterial harmful algal blooms (CyanoHABs). M. aeruginosa blooms have the potential to produce neurotoxins and peptide hepatotoxins, such as microcystins and lipopolysaccharides (LPSs). Currently, technologies for CyanoHAB control do not provide any ultimate solution because of the secondary pollution associated with the control measures. In this study, we attempted to use the peptide HPA3NT3-A2, which has been reported to be nontoxic and has antimicrobial properties, for the development of an eco-friendly control against CyanoHABs. HPA3NT3-A2 displayed significant algicidal effects against M. aeruginosa cells. HPA3NT3-A2 induced cell aggregation and flotation (thereby facilitating harvest), inhibited cell growth through sedimentation, and eventually destroyed the cells. HPA3NT3-A2 had no algicidal effect on other microalgal species such as Haematococcus pluvialis and Chlorella vulgaris. Additionally, HPA3NT3-A2 was not toxic to Daphnia magna. The algicidal mechanism of HPA3NT3-A2 was intracellular penetration. The results of this study suggest the novel possibility of controlling CyanoHABs using HPA3NT3-A2.
[en] This is the first experimental study to compare difference in the development of tolerance against toxic Microcystis among multi-species of cladocerans (Daphnia, Moina and Ceriodaphnia) pre-exposed to two M. aeruginosa PCC7820 strains (MC-containing and MC-free). Zooplankton were divided into S population (fed Scenedesmus), M-F population (fed Scenedesmus + MC-free Microcystis), and M-C population (fed Scenedesmus + MC-containing Microcystis). M-F and M-C populations were pre-exposed to Microcystis strains for 4 weeks, and their newborns were collected for experiments. A pre-exposure to MC-containing or MC-free Microcystis increased tolerance against toxic Microcystis. The marked increases in survival rate and median lethal time (LT5, 100-194% increase) in the M-C population of Ceriodaphnia suggest that small-sized cladocerans may develop stronger tolerance against Microcystis than large-sized ones when both groups are exposed to toxic Microcystis. This may explain why dominant Daphnia is usually replaced by small-sized cladocerans when cyanobacteria bloomed in summer in eutrophic lakes. - Three cladocerans pre-exposed to Microcystis developed different tolerance against toxic Microcystis, explaining zooplankton succession with blooms
[en] Many filamentous cyanobacteria were isolated from different places: fields, ponds, polluted water and soils from Muredkey and Kasur tanneries area, near Lahore, Pakistan. Different media like BG 11 medium, Bold Basal medium, Chu's number 10 medium, Gorham's medium and modified SAG medium, in standard forms and with slight variations of ingredients, different pH, temperature and light regimes were checked for the optimum growth of isolates. The isolation procedure was repeated with different concentrations of chromium to select the resistant strains, These selected strains grew on chromium of range 100-200 micro gml/sup -1/ in BG 11 medium. Cyanobacteria were maintained in solid and in liquid media with/without shaking. Cyanobacterial strains were collected from natural habitats that were accompanied by a diversified group of organisms including bacteria, protozoan and rotifers etc. In order to eliminate these agents termed as contaminants, we used several methods including phenol treatment, use of antibiotic and careful manual picking of filamentous cyanobacteria. Resistance of these strains against different heavy metal (ZnSO/sub 4/, MnSO/sub 4/, NiSO/sub 4/, CoCl/sub 2/, Pb (NO/sub 3/)/sub 3/, CuSO/sub 4/, HgCl/sub 2/, AgNO/sub 3/ and CdCl/sub 2/) and antibiotics (erythromycin, streptomycin, kanamycin, chloramphenicol and neomycin) was evolved. Optimum temperature was 35 deg. C with pH 9 for the reduction of Cr (VI) in to Cr (III) in majority. (author)
[en] We investigated photo-biological H2 production by two N2-fixing marine cyano-bacterial strains, MAL-CB031 and Miami BG 043511. Optimal temperature and salinity for the maximum growth were quite lower in the temperate strain MAL-CB031 than those in the subtropical stain Miami BG 043511. Both strains grow normally even in seawater-based modified f/2-N media (without any added inorganic nitrogen) for extended periods, showing up their N2-fixing ability. The first detection of the photo-biologically produced H2 was made at 24 h and 36 h after the onset of the incubation in N2-fixing and synchronized cells (NF-SN cells) and non-N2-fixing and un-synchronized cells (xNF-xSN cells), respectively. Maximal accumulation of H2 in the 25-ml micro-Fernbach flasks were 1.18 and 0.70 ml/5 ml-suspension in MAL-CB031 and Miami BG 043511, respectively. Present study would be recorded as the first challenge for the photo-biological H2 production by Korean marine cyano-bacterial strains. (authors)
[en] To explore the mechanisms and influence factors on the production of 2,4,6-trichloroanisole (2,4,6-TCA) in surface waters, the 2,4,6-TCA formation potential (FP) test was conducted by incubating the real lake water with the addition of 2,4,6-trichlorophenol (2,4,6-TCP) precursor. Besides bacteria and fungi, two common cyanobacteria and algae species, i.e., Chlorella vulgaris and Anabaena flos-aquae, have been proved to have strong capabilities to produce 2,4,6-TCA, which may contribute the high 2,4,6-TCA FP (152.2 ng/L) of lake water. The microbial O-methylation of 2,4,6-TCP precursor is catalyzed by chlorophenol O-methyltransferases (CPOMTs), and their characteristics were identified by adding inductive methyl donors or excluding microorganisms via ultrafiltration. The results indicated both S-adenosyl methionine (SAM) dependent and non-SAM dependent CPOMTs played important roles; extracellular CPOMTs also participated in the biosynthesis of 2,4,6-TCA. Moreover, investigating the effects of various environmental factors revealed initial 2,4,6-TCP processor concentration, temperature, pH and some divalent metal cations (i.e., Mn2+, Mg2+ and Zn2+) had obvious effects on the production of 2,4,6-TCA. - Highlights: • The production of 2,4,6-TCA by cyanobacteria/algae was revealed for the first time. • Both SAM dependent and non-SAM dependent CPOMTs played important roles. • Extracellular CPOMTs has been proved to participate in biosynthesis of 2,4,6-TCA. • Temperature, pH, and metal ions have obvious effects on biosynthesis of 2,4,6-TCA. • Several strategies have been proposed for the control of 2,4,6-TCA. - The biosynthesis of 2,4,6-TCA was first reported in cyanobacteria and algae species in the lake water, in which various chlorophenol O-methyltransferases were involved.