Diversity,taxonomy and autecology of autochtonous epipelic cyanobacteria of the genus <Emphasis Type="Italic">Komvophoron</Emphasis> (Borziaceae,Oscillatoriales): a study on populations from the Czech Republic and British Isles

Epipelic cyanobacteria were studied in bottom sediments from ponds and lakes in the United Kingdom and the Czech Republic, covering a trophic gradient from deep, oligotrophic, glacial lakes to shallow, eutrophic, urban manmade ponds. Although many planktic species were observed, the most frequently occurring cyanobacteria were the motile filamentous genera Oscillatoria, Phormidium, Pseudanabaena and Komvophoron. These genera represent autochtonous epipelic assemblages, occurring in upper surface layers of the sediments throughout the year and exhibiting seasonal variation in their abundancy. The occurrence of individual Komvophoron species was influenced by sediment quality, particularly the proportions of fine mud and organic detritus. A new species Komvophoron hindakii sp. nov. is described. Morphological features, autecology and occurrence of all the Komvophoron-like morphospecies found are discussed.     

Bioactive compounds from Pseudanabaena species (Cyanobacteria)

Bioactive products of the multicellular filamentous benthic cyanobacterium, Pseudanabaena species, isolated from wastewater stabilization ponds at Marrakech, were tested against some pathogenic micro-organisms. Extracellular and intracellular products released by this blue-green alga in the stationary, growth phase, reduced the survival of Escherichia coli, Salmonella sp., Staphylococcus aureus and Candida albicans, and stimulated the growth of non-O1 V. cholerae, whereas no significant effect was noted on the growth of Candida tropicalis. Intracellular substances (methanolic extract) had a stronger inhibitory effect on these micro-organisms than that produced by extracellular substances. These antibacterial and antifungal substances may have a pharmacological value. They may have an important ecological effect on the composition of the bacterial community in Marrakech stabilization ponds when blooms of Pseudanabaena species occurred in this sewage treatment ecosystem during hot periods.     

Can tropical freshwater zooplankton graze efficiently on cyanobacteria?

Zooplankton may at times graze cyanobacteria. However, their top-down effects are considered to be low, particularly in tropical regions dominated by small-size grazers that may be unable to consume efficiently filamentous or colonial species. Recently, cyanobacteria blooms were reported in the Senegal River hydrosystem. We conducted feeding experiments to assess the ability of copepods (Pseudodiaptomus hessei and Mesocyclops ogunnus), cladocerans (Moina micrura and Ceriodaphnia cornuta), and rotifers (Brachionus angularis, B. falcatus, and Keratella sp.) to control different cyanobacteria (Cylindrospermopsis raciborskii, Anabaena solitaria, A. flos-aquae, and Microcystis aeruginosa). None of the zooplankton species ingested M. aeruginosa. Mesocyclops ogunnus did not consume any of the cyanobacteria. Both cladocerans consumed the smallest filaments of cyanobacteria, whereas all the rotifers and P. hessei consumed a broader food-size spectrum. The functional feeding responses suggest that the concentration and size of the filaments are not the sole criteria for food consumption. The high zooplankton community grazing rates, estimated by applying the clearance rates measured in the laboratory to the in situ zooplankton abundance, indicate that grazing by zooplankton potentially constitutes an important controlling factor for the filamentous cyanobacteria in the tropics.     

Cyanophycean blooms in the reservoir of Val Joly (northern France) and their development in downstream rivers

A study was carried out in 1992 on the Val Joly reservoir and the rivers situated downstream: the River Helpe Majeure and the canalized Sambre into which it flows 40 km below the reservoir. Each year, blooms of blue-green algae occur in the reservoir. They are dominated by species such as Aphanizomenon flos-aquae (L.) Ralfs in 1991 or Pseudanabaena tenuis Koppe and Oscillatoria pseudogeminata G. Schmid in 1992. A typical fluvial composition of the phytoplankton was mostly restored above the confluence with the Sambre. Nevertheless, significant quantities of Oscillatoria and Pseudanabaena have been observed in the River Sambre, just below its confluence with the Helpe Majeure. The environmental conditions in the River Sambre do not allow Aphanizomenon to develop, but could favour Oscillatoria blooms.     

Effects of barley straw (Hordeum vulgare) on freshwater and brackish phytoplankton and cyanobacteria

A short-term laboratory study was conductedto investigate the effect of barley strawin controlling several common phytoplanktonand cyanobacterial species. Following aone-month incubation of barley straw incoarsely filtered fresh Potomac River andbrackish Patuxent River waters, the growthof six autotrophic taxa was followed inculture. Barley straw slurry reduced theyield of three taxa (Ankistrodesmusfalcatus, Chlorella capsulata, Isochrysis sp.) in comparison withcultures not receiving the slurry. Although no significant changes in growthwere detected with three other taxa (Cyclotella sp., Prorocentrumminimum, freshwater Pseudanabaenasp.), some patterns indicated potentialimpacts of the barley straw. First, ahigher addition of straw to Cyclotella sp. resulted in a lower biomassaccumulation than in cultures receivinglower levels. Second, the bloom-formingdinoflagellate Prorcentrum minimumwas apparently stimulated at low barleystraw levels, perhaps suggesting conditionsassociated with the straw(metals-chelation, bacterial-producednutrients) might stimulate dinoflagellategrowth. Third, species shifts wereobserved in two of the cultures, withbarley straw favoring shifts from Isochrysis to a Cyclotella sp. –Thalassiosira sp. mixture and shiftsfrom Pseudanabaena to a Pseudanabaena – Scenedesmus mixture. These results provide new records for thesusceptibility of freshwater and brackishphytoplankton taxa to barley strawexposure, including species-specificresponses and shifts in species dominancein mixed assemblages.     

热带直流型水库蓝藻季节变化特征

于2004年调查了广东省飞来峡和深圳两座直流型水库的蓝藻季节分布特征。共检到蓝藻17属,绝大多数为丝状体种类。常见属有假鱼腥藻(Pseudanabaena)、微囊藻(Microcystis)和蓝纤维藻(Dactylococcopsis)。蓝藻细胞密度为5-2052个细胞ml-1。深圳水库最高蓝藻细胞密度出现在6月,其中丝状蓝藻的相对丰度在75%以上;飞来峡水库最高蓝藻细胞密度出现在12月,丝状蓝藻的相对丰度达到90%。水动力学条件是限制蓝藻丰度和种类的主要环境因子。由于飞来峡水库的水力滞留时间变化较大,所以蓝藻季节性变化受水动力学条件的影响比深圳水库的大。假鱼腥藻等丝状蓝藻更适合在水库中生长,特别是在氮磷营养水平较高,水力滞留时间明显增加时,其细胞密度将大幅度上升。     

淡水藻种库(FACHB)库藏产2-MIB蓝藻的鉴定及其产嗅特征研究

为认识产二甲基异莰醇(2-MIB)蓝藻的形态和产嗅特征,从国家水生生物种质资源库淡水藻种库中筛选出24株可产2-MIB藻株,描述了这些藻株的形态特征和生境分布。结合形态和16S rRNA基因分析对藻株进行物种鉴定复核,修订了部分库藏藻株物种名称,例如发现库藏产2-MIB的浮丝藻属种类应当被重新鉴定为拉氏拟浮丝藻或索状气丝藻。基于mic基因系统发育树分析,显示蓝藻mic基因形成5个分支。通过2-MIB含量检测发现,不同藻株间单个细胞总2-MIB含量为6—2549 fg/cell,其含量通常为拉氏拟浮丝藻>索状气丝藻>灰假鱼腥藻。研究提供了产2-MIB蓝藻的形态、分子、生态和产嗅特性等的基础数据,首次报道气丝藻、沙丝藻、苏打丝藻种类可产2-MIB,并在国内首次报道了产2-MIB的微鞘藻,为进一步研究产2-MIB蓝藻生理生态特性提供重要的实验材料和科学依据。     

Selective inhibition of toxic cyanobacteria by β-carboline-containing bacterium Bacillus flexus isolated from Saudi freshwaters

A bacterial strain SSZ01 isolated from a eutrophic lake in Saudi Arabia dominated by cyanobacterial blooms, showed an antialgal activity against cyanobacteria species. Based on the analysis of the 16S rDNA gene sequence, the isolated strain (SSZ01) most likely belonged to the genus Bacillus with a 99% similarity to Bacillus flexus strain EMGA5. The thin layer chromatography (TLC) analysis of the ethyl acetate extract of this bacterium revealed that this strain can produce harmine and norharmane compared to different β-carboline analog standards. Harmine and norharmane were also detected in considerable amounts in bacterial growth medium, indicating a potential excretion of these compounds into the aquatic environment. The crude extract of Bacillus flexus as well as pure materials of harmine and norharmane inhibited the growth of tested species of cyanobacteria. However, the bacterial crude extract has a higher toxicity against tested species of cyanobacteria than harmine and norharmane. In addition, harmine was more toxic to cyanobacteria than norharmane. On the other hand, neither pure compounds of harmine and norharmane nor crude bacterial extract showed any antialgal activity against tested species of green algae. The results of the present study suggest that B. flexus SSZ01 or its crude extract containing harmine and norharmane could be a candidate for the selective control of cyanobacterial blooms without affecting other algal species.     

Photosynthetic adaptation to light availability shapes the ecological success of bloom-forming cyanobacterium Pseudanabaena to iron limitation

The poorly understood filamentous cyanobacterium Pseudanabaena is commonly epiphytic on Microcystis colonies and their abundances are often highly correlated during blooms. The response and adaptation of Microcystis to iron limitation have been extensively studied, but the strategies Pseudanabaena uses to respond to iron limitation are largely unknown. Here, physiological responses to iron limitation were compared between one Pseudanabaena and two Microcystis strains grown under different light intensities. The results showed that low-intensity light exacerbated, but high-intensity light alleviated, the negative effect of iron limitation on Pseudanabaena growth relative to two Microcystis strains. It was found that robust light-harvesting and photosynthetic efficiency allowed adaptation of Pseudanabaena to low light availability relative to two Microcystis strains only during iron sufficiency. The results also indicated that a larger investment in the photosynthetic antenna probably contributed to light/iron co-limitation of Pseudanabaena relative to two Microcystis strains under both light and iron limitation. Furthermore, the lower antenna pigments/chlorophyll a ratio and photosynthetic efficiency, and higher nonphotochemical quenching and saturation irradiance provided Pseudanabaena photoadaptation and photoprotection advantages over the two Microcystis strains under the high-light condition. The lower investment in antenna pigments of Pseudanabaena than the two Microcystis strains under high-light intensity is likely an efficient strategy for both saving iron quotas and decreasing photosensitivity. Therefore, when compared with Microcystis, the high plasticity of antenna pigments, along with the excellent photoadaptation and photoprotection ability of Pseudanabaena, probably ensures its ecological success under iron limitation when light is sufficient.     

Variability in Chemical Composition and Antimicrobial Activity of Mentha pulegium L. Essential Oil,Cultivated under Different Plant Growth Promoting Rhizobacteria

The aim of present work was to study the essential oil chemical composition and antimicrobial activity of cultivated Mentha pulegium L. under different plant growth promoting rhizobacteria (Pseudomonas fluorescens, Bradyrhizobium sp. and Sinorhizobium meliloti) individually and in consortium. Yield, in plants inoculated with Bradyrhizobium sp. and S. meliloti in consortium, increase significantly relative to control plants. GC and GC/MS analyses pointed to a qualitative and quantitative variability of components. The investigated essential oils were clustered into three chemotypes: piperitenone/1,8-cineol (40.9/29.4 %) chemotype in plants inoculated with Bradyrhizobium sp. individually, S. meliloti individually, and Bradyrhizobium sp. and S. meliloti in consortium, piperitone/menthone (41.8/33.8 %) chemotype in plants inoculated with P. fluorescens individually, P. fluorescens and Bradyrhizobium sp. in consortium, and P. fluorescens and S. meliloti in consortium and pulegone/menthol (47.9/31.5 %) chemotype in control plants. The antimicrobial activity, carried out by the disc diffusion method and the determination of the Minimum Inhibitory Concentration (MIC) against ten microorganisms, varied significantly according to the tested microorganism and the rhizobacterial species used individually or in consortium (inhibition zone: 8.5–33.5 mm; MIC: 0.25–2.5 μL/mL). Our findings provided useful indications to select interesting chemotype within M. pulegium, especially in perspective of its cultivation.     

Alga-lytic activity of Pseudomonas fluorescens against the red tide causing marine alga Heterosigma akashiwo (Raphidophyceae)

A bacterial strain, HAK-13, exhibited strongest activity against Heterosigma akashiwo and was capable of controlling this bloom forming phytoplankton. Based on 16S rDNA sequences and biochemical and morphological characteristics, the strain HAK-13 was determined to be Pseudomonas fluorescens on the basis of 99.9% similarity with reference strains in the DNA databases. The growth of H. akashiwo was strongly suppressed by HAK-13 in all growth phases, with the strongest alga-lytic activity noted against harmful bloom-forming species in the exponential stage (6–22 days). Host range tests showed that HAK-13 also significantly inhibited the growth of Alexandrium tamarense and Cochlodinium polykrikoides but could not destroy Gymnodinium catenatum. P. fluorescens HAK-13 indirectly attacked H. akashiwo by alga-lytic substances that might be located at the compartment of cytoplasmic membrane of the bacterium at a level of 45.86 units/mg of specific activity. The results indicated that P. fluorescens HAK-13 caused cell lysis and death of H. akashiwo, A. tamarense, and C. polykrikoides dramatically and Prorocentrum dentatum slightly. Therefore, P. fluorescens HAK-13 has potential for use as a selective biocontrol of harmful algal blooms.     

Bio-optical characterization of selected cyanobacteria strains present in marine and freshwater ecosystems

The optical properties, i.e., absorption and scattering spectra of ten strains of cyanobacteria from the Baltic Sea and Pomeranian lakes (Aphanizomenon flos-aquae KAC 15, Microcystis aeruginosa CCNP 1101, Anabaena sp. CCNP 1406, Synechocystis salina CCNP 1104, Phormidium sp. CCNP 1317, Nodularia spumigena CCNP 1401, Synechococcus sp. CCNP 1108, Nostoc sp. CCNP 1411, Cyanobacterium sp. CCNP 1105, Pseudanabaena cf. galeata CCNP 1312) grown under low light conditions were investigated. Moreover, the chlorophylls, carotenoids, and phycobilin composition as well as the size structure of chosen cyanobacteria were measured. Studied species revealed high diversity both in optical properties with the absorption spectra similarity index ranging from 0.67 to 0.94 and the pigment composition. The chlorophyll-specific absorption coefficient at 440 nm a _ph *(440) varied between 0.017 and 0.065 m² mg^?1. The influence of the package effect was only observed in the case of large filamentous cyanobacteria like N. spumigena or Nostoc sp. Interestingly, the package effect factor Q _a *(675) for large-celled Anabaena sp. was 0.92. Besides chlorophyll a, only echinenone, β-carotene, and phycocyanin were present in all analyzed cyanobacteria strains. Zeaxanthin, which is widely used as a marker pigment for cyanobacteria, was absent in the toxic N. spumigena and Anabaena sp., which are the species that occur in the Baltic Sea most frequently causing summer cyanobacterial blooms. The investigation also showed that the sample preservation technique can introduce some major errors within the absorption band affected by the phycocyanin absorption.     

Structural Diversity of Bacterial Communities Associated with Bloom-Forming Freshwater Cyanobacteria Differs According to the Cyanobacterial Genus

The factors and processes driving cyanobacterial blooms in eutrophic freshwater ecosystems have been extensively studied in the past decade. A growing number of these studies concern the direct or indirect interactions between cyanobacteria and heterotrophic bacteria. The presence of bacteria that are directly attached or immediately adjacent to cyanobacterial cells suggests that intense nutrient exchanges occur between these microorganisms. In order to determine if there is a specific association between cyanobacteria and bacteria, we compared the bacterial community composition during two cyanobacteria blooms of Anabaena (filamentous and N₂-fixing) and Microcystis (colonial and non-N₂ fixing) that occurred successively within the same lake. Using high-throughput sequencing, we revealed a clear distinction between associated and free-living communities and between cyanobacterial genera. The interactions between cyanobacteria and bacteria appeared to be based on dissolved organic matter degradation and on N recycling, both for N₂-fixing and non N₂-fixing cyanobacteria. Thus, the genus and potentially the species of cyanobacteria and its metabolic capacities appeared to select for the bacterial community in the phycosphere.     

Molecular specificity and detection for Pseudanabaena (cyanobacteria) species based on rbcLX sequences

In decades, Pseudanabaena species have been frequently reported as cyanobacterial bloom components. However, these species are always overlooked because they cannot be observed easily owing to their small sizes. This study aimed to characterize Pseudanabaena species and detect them in field waters by developing an effective DNA marker. A region with approximately 600 bp in the rbcLX sequences was specific to Pseudanabaena species alone compared with other cyanobacterial genera. Therefore, new primers specific for Pseudanabaena were generated. By using this molecular tool, seasonal and spatial dynamics of Pseudanabaena populations of six sites in Lushui Reservoir, China were measured from July 2010 to August 2011. Pseudanabaena species existed in the reservoir throughout the year, and cell abundance ranged between 10⁴ and 10⁶ equivalent cells/L, with the peak at 8.07 × 10⁶ equivalent cells/L. The seasonal dynamics pattern of Pseudanabaena was similar to that of Microcystis but showed a slight lag at the transitional points of water temperature in the reservoir.     

Species‐specific separation of lake plankton reveals divergent food assimilation patterns in rotifers

相似文献   

Production,by filamentous,nitrogen-fixing cyanobacteria,of a bacteriocin and of other antibiotics that kill related strains

Colonies of sixty-five filamentous cyanobacteria were screened for the production of temperate phages and/or antibiotics on solid medium. None of them was observed to release phages. However, seven N₂-fixing strains were found to produce antibiotics very active against other cyanobacteria. The antibiotic produced by Nostoc sp. 78-11 A-E represents a bacteriocin of low molecular weight. Nostoc sp. ATCC 29132 appears to secrete, together with an antibiotic, a protein that inhibits its action.     

Identification of two cyanobacterial strains isolated from the Kotel’nikovskii hot spring of the Baikal rift

Two cyanobacterial strains, Pseudanabaena sp. 0411 and Synechococcus sp. 0431, were isolated from a sample collected in the Kotel’nikovskii hot spring of the Baikal rift. According to the results of light and transmission electron microscopy, as well as of the phylogenetic analysis of the 16S rRNA gene, these cyanobacteria were classified as Pseudanabaena sp. nov. and Synechococcus bigranulatus Skuja. The constructed phylogenetic tree shows that the studied strains are positioned in the clades of cyanobacteria isolated from hydrothermal vents of Asia and New Zealand, separately from marine and freshwater members of these genera, including those isolated from Lake Baikal.     

Relative Uptake of Urea and Ammonium by Dinoflagellates or Cyanobacteria in Shrimp Mesocosms

The relative role of the organic nitrogen source, urea, versus ammonium as a nitrogen source for two species of dinoflagellates was compared with one species of cyanobacteria. Experiments were conducted opportunistically in nutrient-rich marine water during blooms of 34either cyanobacteria or dinoflagellates in outdoor mesocosms. These replicate mesocosms, which were stocked with shrimp fed high-protein formulated feeds, contained high biomasses of phytoplankton (mean chlorophyll a concentrations, 439.2–811.2 μg l⁻¹). ¹⁵N-urea and ammonium uptake rates for dinoflagellate-dominated blooms (Gymnodinium pulchellum-complex (Larsen), Karlodinium micrum (Larsen) (Dinophyceae)) were compared with blooms of the cyanobacterium, Romeria sp. (Cyanophyceae) in mesocosms with mean urea and ammonium concentrations ranging from 2.32 to 3.24 μM, and 7.39 to 64.85 μM, respectively. Urea uptake rates were significantly (p < 0.005) lower than ammonium uptake rates irrespective of which algal species dominated the bloom. Additionally urea uptake rates were not significantly higher in G. pulchellum-complex or K. micrum-dominated blooms than in Romeria sp. blooms. These results suggest that G pulchellum complex and K. micrum may not be gaining a competitive advantage in waters high in dissolved organic matter simply by preferentially utilizing urea. The periodic dominance of these species in highly organic environments, such as shrimp ponds, is likely to have a more complex explanation.     

Using enzymes to remove biofilms of bacterial isolates sampled in the food-industry

The aim of this study was to analyze the cleaning efficiency of polysaccharidases and proteolytic enzymes against biofilms of bacterial species found in food industry processing lines and to study enzyme effects on the composition of extracellular polymeric substances (EPS) and biofilm removal in a Clean-in-Place (CIP) procedure. The screening of 7 proteases and polysaccharidases for removal of biofilms of 16 bacterial species was first evaluated using a microtiter plate assay. The alkaline pH buffer removed more biofilm biomass as well as affecting a larger range of bacterial species. The two serine proteases and α-amylase were the most efficient enzymes. Proteolytic enzymes promoted biofilm removal of a larger range of bacterial species than polysaccharidases. Using three isolates derived from two bacterial species widely found in food processing lines (Pseudomonas fluorescens and the Bacillus cereus group), biofilms were developed on stainless steel slides and enzymatic solutions were used to remove the biofilms using CIP procedure. Serine proteases were more efficient in removing cells of Bacillus biofilms than polysaccharidases. However, polysaccharidases were more efficient in removing P. fluorescens biofilms than serine proteases. Solubilization of enzymes with a buffer containing surfactants, and dispersing and chelating agents enhanced the efficiency of polysaccharidases and proteases respectively in removing biofilms of Bacillus and P. fluorescens. A combination of enzymes targeting several components of EPS, surfactants, dispersing and chelating agents would be an efficient alternative to chemical cleaning agents.     

Culture temperature affects gene expression and metabolic pathways in the 2-methylisoborneol-producing cyanobacterium Pseudanabaena galeata

A volatile metabolite, 2-methylisoborneol (2-MIB), causes an unpleasant taste and odor in tap water. Some filamentous cyanobacteria produce 2-MIB via a two-step biosynthetic pathway: methylation of geranyl diphosphate (GPP) by methyl transferase (GPPMT), followed by the cyclization of methyl-GPP by monoterpene cyclase (MIBS). We isolated the genes encoding GPPMT and MIBS from Pseudanabaena galeata, a filamentous cyanobacterium known to be a major causal organism of 2-MIB production in Japanese lakes. The predicted amino acid sequence showed high similarity with that of Pseudanabaena limnetica (96% identity in GPPMT and 97% identity in MIBS). P. galeata was cultured at different temperatures to examine the effect of growth conditions on the production of 2-MIB and major metabolites. Gas chromatograph–mass spectrometry (GC–MS) measurements showed higher accumulation of 2-MIB at 30 °C than at 4 °C or 20 °C after 24 h of culture. Real-time-RT PCR analysis showed that the expression levels of the genes encoding GPPMT and MIBS decreased at 4 °C and increased at 30 °C, compared with at 20 °C. Furthermore, metabolite analysis showed dramatic changes in primary metabolite concentrations in cyanobacteria grown at different temperatures. The data indicate that changes in carbon flow in the TCA cycle affect 2-MIB biosynthesis at higher temperatures.