Dark accelerates dissolved inorganic phosphorus release of high-density cyanobacteria.

Bloom-forming cyanobacteria dramatically influence nutrient cycling in eutrophic freshwater lakes. The phosphorus (P) assimilation and release of bloom-forming cyanobacteria significantly may also affect the phosphorus source and amounts in water. To understand the phosphorus release process of bloom-forming cyanobacteria below the accumulated surface and sedimentary bloom-forming cyanobacteria, the degradation of bloom-forming cyanobacteria dominated by Microcystis spp. at different cell density in the dark was investigated over a 25-day microcosm experiment. The dissolved inorganic phosphorus (DIP) and dissolved total phosphorus (DTP) contents increased with the increment of cyanobacterial density, and the dark status markedly increased the proportion of DIP in water during the decline period of bloom-forming cyanobacteria. Meanwhile, the process of cyanobacterial apoptosis accompanied by the changes of malondialdehyde (MDA) and phosphatase (AKP) contents, and the increases of superoxide dismutase (SOD) and catalase (CAT) activities of cyanobacteria in the dark, especially in low-density groups (5.23×108 cells L-1), which further affect the physicochemical water parameters. Moreover, the DIP release from high-density cyanobacteria (7.86×107 cells L-1~5.23×108 cells L-1) resulted from the relative abundance of organophosphorus degrading bacteria in the dark. Therefore, the fast decay of cyanobacteria in the dark could accelerate DIP release, the high DIP release amount from accumulated bloom-cyanobacteria provide adequate P quickly for the sustained growth of cyanobacteria.

Responses of freshwater algal cell density to hydrochemical variables in an urban aquatic ecosystem, northern China.

In this paper, the algal cell density of cyanobacteria, green algae, and diatoms and their responses to the hydrochemical factors were analyzed to reveal the structural characteristics of water quality in an urban river. A total of nine sampling sites from upstream to downstream was explored in our study. At each site, the density of algae was identified every week during the wet season (June-October) from 2012 to 2017, and in situ detection was used for the relative 11 hydrochemical variables. The temporal and spatial characteristics of 14 variables were analyzed using a heatmap coupled with the cluster analysis method. The trend of each parameter was analyzed using the smoothing method with locally weighted regression. The nonmetric multidimensional scaling method was employed to detect the temporal and spatial similarities among algae along hydrochemical gradients. The responses of algal density to hydrochemical variables were analyzed using a redundancy analysis. The results showed that the water temperature (Wtemp), pH, dissolved oxygen (DO), cyanobacteria, and diatoms exhibited significant declining trends, and significant increasing trends were shown in the permanganate index, chemical oxygen demand, total nitrogen, ammonia nitrogen, and total phosphorus; the cyanobacteria exhibited certain differences with green algae and diatoms in summer and the downstream areas of the river. The temporal-spatial homogeneity of algal to hydrochemical variables showed the key influencing factors of Wtemp for cyanobacteria density, chlorophyll for green algae density, DO, and pH for diatoms. The results presented here are valuable for deepening our understanding of river ecosystem evaluations and effective environmental management, as well as an important reference for the sustainable development of aquatic biological resources.

Response of chlorophyll d-containing cyanobacterium Acaryochloris marina to UV and visible irradiations.

We have previously investigated the response mechanisms of photosystem II complexes from spinach to strong UV and visible irradiations (Wei et al J Photochem Photobiol B 104:118-125, 2011). In this work, we extend our study to the effects of strong light on the unusual cyanobacterium Acaryochloris marina, which is able to use chlorophyll d (Chl d) to harvest solar energy at a longer wavelength (740 nm). We found that ultraviolet (UV) or high level of visible and near-far red light is harmful to A. marina. Treatment with strong white light (1,200 µmol quanta m(-2) s(-1)) caused a parallel decrease in PSII oxygen evolution of intact cells and in extracted pigments Chl d, zeaxanthin, and α-carotene analyzed by high-performance liquid chromatography, with severe loss after 6 h. When cells were irradiated with 700 nm of light (100 µmol quanta m(-2) s(-1)) there was also bleaching of Chl d and loss of photosynthetic activity. Interestingly, UVB radiation (138 µmol quanta m(-2) s(-1)) caused a loss of photosynthetic activity without reduction in Chl d. Excess absorption of light by Chl d (visible or 700 nm) causes a reduction in photosynthesis and loss of pigments in light harvesting and photoprotection, likely by photoinhibition and inactivation of photosystem II, while inhibition of photosynthesis by UVB radiation may occur by release of Mn ion(s) in Mn4CaO5 center in photosystem II.

Nutrient sequestration, biomass production by microalgae and phytoremediation of sewage water.

The present work was aimed at analysing the role of inoculated microalgae in nutrient dynamics, bioremediation and biomass production of sewage water. Preliminary microscopic analyses of sewage water revealed the presence of different algal groups, with predominance of Cyanophyta. Among the inoculated strains, Calothrix showed highest dry cell weight (916.67 mg L(-1)), chlorophyll and carotenoid content in tap water + sewage water (1:1) treatment. Significant removal of NO3-N ranging from 57-78% and PO4-P (44-91%) was recorded in microalgae inoculated tap water + sewage water. The total dissolved solids and electrical conductivity of tap water + sewage water after incubation with Calothrix sp. decreased by 28.5 and 28.0%, accompanied by an increase in dissolved oxygen from 4.4 to 6.4 mg L(-1) on the 20th day. Our investigation revealed the robustness of Calothrix sp. in sequestering nutrients (N and P), improving water quality and proliferating in sewage water.

Reactive oxygen species are involved in the morphology-determining mechanism of Fremyella diplosiphon cells during complementary chromatic adaptation.

Fremyella diplosiphon modifies the pigment composition of its major light-harvesting complexes, i.e. phycobilisomes, and cell and filament morphology according to ambient light quality in a process termed complementary chromatic adaptation (CCA). The cells are red in colour and rectangular shaped, and filaments are longer under green light (GL), in contrast with blue-green, spherical cells and shorter filaments under red light (RL). In this study, we report that wild-type (WT) UTEX 481 and WT-pigmented, shortened filament strain SF33 of F. diplosiphon accumulate reactive oxygen species (ROS) under both GL and RL, with the level of oxidative stress being higher under RL as compared with GL. During CCA, higher levels of ROS under RL are correlated with the RL-specific spherical cell shape and filament fragmentation - cells exhibiting elevated levels of ROS under RL have reduced cell length, yet the width of cells is not affected. Addition of ascorbic acid to RL-grown cultures resulted in lower ROS levels and a concomitant shift to GL-associated cellular morphology, i.e. an increased cell length. This observation identifies an RL-dependent oxidative-stress-mediated regulation of morphogenesis in a bacterial system. Spherical cell morphology may result from ROS-dependent changes in the cell membrane integrity or cell wall loosening and associated cell expansion.

[Vertical migration of algal cells in the Daning River Bay of the Three Gorges Reservoir].

To support the basic data for forecast of algal blooms, circadian vertical migration experiment was carried out in the Daning River Bay of the Three Gorges Reservoir in July, 2011. The results were as follows: in this period, different algal species were found in the Daning River Bay, including cyanobacteria, green algae, dinoflagellates and diatoms etc; the distribution of algal cells was uneven, 72.5%-76.2% of algal cells aggregated at 0.5-4.0 m water depths from 10:00 AM to 10:00 AM next day, but 7.5%-16.3% of algal cells aggregated at 0-0.5 m. Morisita's indexes (MI) of algal cells were from 1.41 to 1.97 in day time, and from 1.17 to 1.55 at night. Morisita's indexes of chlorophyll a(Chla)were from 1.31 to 1.59 in day time, and from 1.17 to 1.39 at night. The vertical migration also occurred at 0.5-4.0 m water depths. The algal density was not significantly related with the concentrations of nutrient except that of dissolved total phosphorus (DTP) (r = 0.89). The algal density was also influenced by water temperature (WT), pH and specific conductance (SPC), and the correlation coefficients were 0.96, 0.97 and -0.99, respectively.

Chemotaxonomy of heterocystous cyanobacteria using FAME profiling as species markers.

The fatty acid methyl ester (FAME) analysis of the 12 heterocystous cyanobacterial strains showed different fatty acid profiling based on the presence/absence and the percentage of 13 different types of fatty acids. The major fatty acids viz. palmitic acid (16:0), hexadecadienoic acid (16:2), stearic acid (18:0), oleic acid (18:1), linoleic (18:2), and linolenic acid (18:3) were present among all the strains except Cylindrospermum musicola where oleic acid (18:1) was absent. All the strains showed high levels of polyunsaturated fatty acid (PUFAs; 41-68.35%) followed by saturated fatty acid (SAFAs; 1.82-40.66%) and monounsaturated fatty acid (0.85-24.98%). Highest percentage of PUFAs and essential fatty acid (linolenic acid; 18:3) was reported in Scytonema bohnerii which can be used as fatty acid supplement in medical and biotechnological purpose. The cluster analysis based on FAME profiling suggests the presence of two distinct clusters with Euclidean distance ranging from 0 to 25. S. bohnerii of cluster I was distantly related to the other strains of cluster II. The genotypes of cluster II were further divided into two subclusters, i.e., IIa with C. musicola showing great divergence with the other genotypes of IIb which was further subdivided into two groups. Subsubcluster IIb(1) was represented by a genotype, Anabaena sp. whereas subsubcluster IIb(2) was distinguished by two groups, i.e., one group having significant similarity among their three genotypes showed distant relation with the other group having closely related six genotypes. To test the validity of the fatty acid profiles as a marker, cluster analysis has also been generated on the basis of morphological attributes. Our results suggest that FAME profiling might be used as species markers in the study of polyphasic approach based taxonomy and phylogenetic relationship.

The use of cyanobacteria as filler in nitrocellulose capillaries improves ultrastructural preservation of immature barley pollen upon high pressure freezing.

The high pressure freezing (HPF) followed by freeze substitution technique has advantages over chemical fixation in the context of preserving sample ultrastructure. However, when HPF is applied to cultured pollen grains, the large intercellular spaces present lead to a poor level of ultrastructure preservation. We report here that the mixing of cyanobacteria with immature barley pollen grains succeeded in greatly reducing the volume of liquid present between the large pollen grains, and so improved the loading of the sample into a nitrocellulose capillary. The use of yeast or cyanobacteria paste to surround the filled capillaries was beneficial in speeding the transfer of heat during the freezing process. This modification of the HPF method resulted in a greatly improved level of ultrastructure preservation.

Linking chemistry and genetics in the growing cyanobactin natural products family.

Ribosomal peptide natural products are ubiquitous, yet relatively few tools exist to predict structures and clone new pathways. Cyanobactin ribosomal peptides are found in ~30% of all cyanobacteria, but the connection between gene sequence and structure was not defined, limiting the rapid identification of new compounds and pathways. Here, we report discovery of four orphan cyanobactin gene clusters by genome mining and an additional pathway by targeted cloning, which represented a tyrosine O-prenylating biosynthetic pathway. Genome mining enabled discovery of five cyanobactins, including peptide natural products from Spirulina supplements. A phylogenetic model defined four cyanobactin genotypes, which explain the synthesis of multiple cyanobactin structural classes and help direct pathway cloning and structure prediction efforts. These strategies were applied to DNA isolated from a mixed cyanobacterial bloom containing cyanobactins.

Metabolic adaptations in a H2 producing heterocyst-forming cyanobacterium: potentials and implications for biological engineering.

Nostoc punctiforme ATCC 29133 is a photoautotrophic cyanobacterium with the ability to fix atmospheric nitrogen and photoproduce hydrogen through the enzyme nitrogenase. The H(2) produced is reoxidized by an uptake hydrogenase. Inactivation of the uptake hydrogenase in N. punctiforme leads to increased H(2) release but unchanged rates of N(2) fixation, indicating redirected metabolism. System-wide understanding of the mechanisms of this metabolic redirection was obtained using complementary quantitative proteomic approaches, at both the filament and the heterocyst level. Of the total 1070 identified and quantified proteins, 239 were differentially expressed in the uptake hydrogenase mutant (NHM5) as compared to wild type. Our results indicate that the inactivation of uptake hydrogenase in N. punctiforme changes the overall metabolic equilibrium, affecting both oxygen reduction mechanisms in heterocysts as well as processes providing reducing equivalents for metabolic functions such as N(2) fixation. We identify specific metabolic processes used by NHM5 to maintain a high rate of N(2) fixation, and thereby potential targets for further improvement of nitrogenase based H(2) photogeneration. These targets include, but are not limited to, components of the oxygen scavenging capacity and cell envelope of heterocysts and proteins directly or indirectly involved in reduced carbon transport from vegetative cells to heterocysts.

Morphological and genetic evidence that the cyanobacterium Lyngbya wollei (Farlow ex Gomont) Speziale and Dyck encompasses at least two species.

Dense blooms of the cyanobacterium Lyngbya wollei are increasingly responsible for declining water quality and habitat degradation in numerous springs, rivers, and reservoirs. This research represents the first molecular phylogenetic analysis of L. wollei in comparison with the traditional morphological characterization of this species. Specimens were collected from several springs in Florida and a reservoir in North Carolina. Segments of the small-subunit (SSU) rRNA and nifH genes were PCR amplified, cloned, and sequenced. The phylogenetic analysis of the SSU rRNA gene revealed sequences that fell into three distinct subclusters, each with >97% sequence similarity. These were designated operational taxonomic unit 1 (OTU1), OTU2, and OTU3. Similarly, the nifH sequences fell into three distinct subclusters named S1, S2, and S3. When either bulk samples or individual filaments were analyzed, we recovered OTU1 with S1, OTU2 with S2, and OTU3 with S3. The coherence between the three SSU rRNA gene and nifH subclusters was consistent with genetically distinct strains or species. Cells associated with subclusters OTU3 and S3 were significantly wider and longer than those associated with other subclusters. The combined molecular and morphological data indicate that the species commonly identified as L. wollei in the literature represents two or possibly more species. Springs containing OTU3 and S3 demonstrated lower ion concentrations than other collection sites. Geographical locations of Lyngbya subclusters did not correlate with residual dissolved inorganic nitrogen or phosphorus concentrations. This study emphasizes the need to complement traditional identification with molecular characterization to more definitively detect and characterize harmful cyanobacterial species or strains.

Microcosm experiments of oil degradation by microbial mats. II. The changes in microbial species.

The influence of microbial mats on the degradation of two crude oils (Casablanca and Maya) and the effect of oil pollution on the mat structure were assessed using model ecosystems, prepared under laboratory conditions subject to tidal movements, from pristine Ebro Delta microbial-mat ecosystems. Both selected oils are examples of those currently used for commercial purposes. Casablanca crude oil is aliphatic with a low viscosity; Maya represents a sulphur-rich heavy crude oil that is predominantly aromatic. In the unpolluted microcosms, Microcoleus chthonoplastes-, Phormidium- and Oscillatoria-like were the dominant filamentous cyanobacterial morphotypes, whilst Synechoccocus-, Synechocystis- and Gloeocapsa-like were the most abundant unicellular cyanobacteria. After oil contamination, no significant changes of chlorophyll a and protein concentrations were observed, though cyanobacterial diversity shifts were monitored. Among filamentous cyanobacteria, M. chthonoplastes-like morphotype was the most resistant for both oils, unlike the other cyanobacteria, which tolerated Casablanca but not Maya. Unicellular cyanobacteria seemed to be resistant to pollution with both essayed oils, with the exception of the morphotype resembling Gloeocapsa, which was sensitive to both oils. The crude-oil addition also had a significant effect on certain components of the heterotrophic microbial community. Casablanca oil induced an increase in anaerobic heterotrophic bacteria, whereas the opposite effect was observed in those heterotrophs when polluted with Maya oil. The overall results, microbiological and crude-oil transformation analysis, indicate that the indigenous community has a considerable potential to degrade oil components by means of the metabolic cooperation of phototrophic and heterotrophic populations.

The impact of surface-adsorbed phosphorus on phytoplankton Redfield stoichiometry.

The Redfield ratio of 106 carbon:16 nitrogen:1 phosphorus in marine phytoplankton is one of the foundations of ocean biogeochemistry, with applications in algal physiology, palaeoclimatology and global climate change. However, this ratio varies substantially in response to changes in algal nutrient status and taxonomic affiliation. Here we report that Redfield ratios are also strongly affected by partitioning into surface-adsorbed and intracellular phosphorus pools. The C:N:surface-adsorbed P (80-105 C:15-18 N:1 P) and total (71-80 C:13-14 N:1 P) ratios in natural populations and cultures of Trichodesmium were close to Redfield values and not significantly different from each other. In contrast, intracellular ratios consistently exceeded the Redfield ratio (316-434 C:59-83 N:1 intracellular P). These high intracellular ratios were associated with reduced N2 fixation rates, suggestive of phosphorus deficiency. Other algal species also have substantial surface-adsorbed phosphorus pools, suggesting that our Trichodesmium results are generally applicable to all phytoplankton. Measurements of the distinct phytoplankton phosphorus pools may be required to assess nutrient limitation accurately from elemental composition. Deviations from Redfield stoichiometry may be attributable to surface adsorption of phosphorus rather than to biological processes, and this scavenging could affect the interpretation of marine nutrient inventories and ecosystem models.

[Spatial integration of partners and heteromorphism of cyanobacterium Nostoc muscoum CALU 304 in mixed culture with Rauwolfia]. / Prostranstvennaia integratsiia partnerov i geteromorfizm tsianobakteriiNostoc muscorum CALU 304 v smeshanoi kul'ture s tkan'iu rauvol'fii.

A comparative morphological study was conducted of Nostoc muscorum CALU 304 grown either as a pure culture on standard media or as a mixed culture with Rauwolfia callus tissue on a medium for plant tissue cultivation. The interaction of the cyanobacterial and plant partners results in their spatial integration into aggregates of specific anatomy, which arise periodically during the mixed culture growth. The morphology of the cyanobacterial cells varies depending on their localization in the combined aggregate. The degree of cyanobacterial heteromorphism increases with time of growth of the association. Evidence of the plant origin of the factors inducing heteromorphic changes in N. muscorum was obtained, as well as evidence indicating that these factors can rapidly diffuse in agarized medium. A conclusion is inferred that the heteromorphic cells correspond to bacterial forms that appear during unbalanced growth as an adaptation to altered environmental conditions.

The antipsoriatic compound anthralin influences bioenergetic parameters and redox properties of energy transducing membranes.

Bioenergetic parameters and redox properties of energy transducing membranes in rat liver mitochondria and cyanobacteria were investigated in the presence of the antipsoriatic compound anthralin (1,8-dihydroxy-9-anthrone). Transmembrane pH and electrical gradients were determined using electron paramagnetic resonance spectroscopy. In mitochondria, ubiquinones 9,10 and other redox components of the electron transport chain are reduced by anthralin; the proton motive force is increased. In the absence of ADP, anthralin slightly stimulates mitochondrial cyanide-insensitive oxygen consumption. It is suggested that increased cyanide-insensitive respiration is due to enhanced autoxidation of mitochondrial components and/or catalyzed oxidation of anthralin. In the presence of ADP mitochondrial respiration is decreased, and ATP synthesis is inhibited. Uncoupler-induced mitochondrial respiration is also decreased by anthralin, indicating inhibition of the electron transport chain. In the cyanobacterium Synechococcus PCC 6311 anthralin increases the pH gradient and decreases ATP levels. Thus, anthralin acts as an electron donor to membrane associated redox components and inhibits ATP synthesis in two different biologic systems. In human keratinocytes oxygen metabolism is influenced by anthralin in a similar pattern as in isolated mitochondria, and ATP content is decreased. Because anthralin reacts with redox components in different biologic membranes, alterations of subcellular/cellular redox status and energy metabolism might contribute significantly to its antiproliferative activity.

Stimulation of cell division by croton oil in blue-green bacteria.

The potent tumor-promoting agent croton oil, which has been shown previously to be strongly mitogenic in mammalian cells, stimulates cell division in snake mutants of the blue-green bacterium Agmenellum quadruplicatum.

Blue-green algae: why they become dominant.

The injection of carbon dioxide and the addition of nitrogen and phosphorus to a lake population dominated by blue-green algae results in a rapid shift to dominance by green algae. The basis for the change and its implications are discussed.