Three-channel false colour AFM images for improved interpretation of complex surfaces: A study of filamentous cyanobacteria

Imaging signals derived from the atomic force microscope (AFM) are typically presented as separate adjacent images with greyscale or pseudo-colour palettes. We propose that information-rich false-colour composites are a useful means of presenting three-channel AFM image data. This method can aid the interpretation of complex surfaces and facilitate the perception of information that is convoluted across data channels. We illustrate this approach with images of filamentous cyanobacteria imaged in air and under aqueous buffer, using both deflection-modulation (contact) mode and amplitude-modulation (tapping) mode. Topography-dependent contrast in the error and tertiary signals aids the interpretation of the topography signal by contributing additional data, resulting in a more detailed image, and by showing variations in the probe-surface interaction. Moreover, topography-independent contrast and topography-dependent contrast in the tertiary data image (phase or friction) can be distinguished more easily as a consequence of the three dimensional colour-space.     

Health-Risks Assessment of Dinghy Sailing in Avon and Exposure to Cyanobacteria (Blue-Green Algae)

In 1990, the health hazards associated with cyanobacteria attracted widespread interest. In this study, the risks associated with dinghy sailing on two water reservoirs in Avon were examined when the National Rivers Authority concentration threshold for 'a potential to cause harm'was exceeded at one of these sites. No unusual illnesses were identified and the patterns of reported minor health symptoms were similar at each site. These patterns were also similar to those found amongst freshwater dinghy sailors in Hampshire when the NRA cyanobacteria threshold was exceeded, and similar to patterns of minor morbidity identified amongst dinghy sailors in marine waters when the EC bathing water quality standards are met. The consistency of these findings from three different studies suggests that present Royal Yachting Association guidelines for dinghy sailors are adequate to safeguard their health from cyanobacteria exposure.     

Hydrogenases and photobiological hydrogen production utilizing nitrogenase system in cyanobacteria

We constructed three hydrogenase mutants from Anabaena sp. PCC 7120: ΔhupL (deficient in uptake hydrogenase), ΔhoxH (deficient in bidirectional hydrogenase), and ΔhupL/ΔhoxH (deficient in both genes), and showed that the Δhup and ΔhupL/ΔhoxH produced H₂ at a rate 4–7 times that of wild-type under optimal conditions (Appl. Microbiol. Biotechnol. 58 (2002) 618). We have studied H₂ producing activity of Δhup in more detail. H₂ producing activity of Δhup cells was moderately improved in older cultures when 1% CO₂ was added to the bubbling air. The efficiency of light energy conversion to H₂ by the ΔhupL mutant at its highest H₂ production stage was 1.0–1.6% at an actinic visible light intensity of lower than 50 W/m² under argon atmosphere, and the activity lasted for at least 35 min. At 250 W/m², H₂ producing activity gradually decreased with illumination time.     

蓝藻生物资源的开发与应用

利用环境废弃物蓝藻,开发SiO2新材料和抗紫外农药缓释剂型。合成了形貌规整、平均粒径为1.5μm、粒径分布较窄的SiO2实心与空心微球,采用TG、SEM、FE-SEM对其进行了表征,研究了其制备液相色谱固定相的方法和分离纯化蛋白质的条件。以蓝藻为载体,制备了农药(戊唑醇、阿维菌素、甲维盐)抗紫外缓释剂,研究了蓝藻对上述农药的吸附、缓释行为和抗紫外性能,吸附量达到160.81 mg/g,半量释放时间在40 d左右,蓝藻吸附农药样品与商品化制剂相比,抗紫外能力相对提高了56.4%,相对降低了农药的大田使用量,探索了蓝藻作为农药制剂载体的可行性。     

Long term diazotrophic cultivation induces phycobiliprotein production in <i>Anabaena variabilis</i> IMU8

Cyanobacteria are considered as a sustainable feedstock for the production of biochemically active compounds such as phycobiliproteins (PBPs). In this study, the impact of nitrogen (N) and phosphorus (P) availability on PBP production of “N-free acclimated” Anabaena variabilis IMU8 was analyzed. Upon isolation and identification, the cyanobacterium has been maintained in N-free BG-11 medium for more than 20 months. For experimentation, the strain was incubated in N-replete, N-depleted, N-P-depleted BG-11 medium. Long-term diazotrophic cultivation of A. variabilis IMU8 resulted in elevated PBP productivity with a limited impact on growth. When compared to N-depleted ones, N supply stimulated a slight induction of growth and total saccharide production, but total protein content did not change while PBP production decreased. On the other hand, N-P-depletion resulted in decreased growth rate along with reduced total protein and PBP production while rapid induction of total saccharide production was recorded. Fourier transform infrared spectroscopy results refer that membrane-bound oligosaccharides may have regulatory roles for PBP production in A. variabilis IMU8 during long term diazotrophic cultivation.     

Extended H2 photoproduction by N2-fixing cyanobacteria immobilized in thin alginate films

Screening of the University of Helsinki Culture Collection for naturally good H₂ producing cyanobacteria recently revealed several promising strains. One of the superior strains is Calothrix 336/3, an N₂-fixing heterocystous filamentous cyanobacterium. Making use of an important feature of the Calothrix 336/3 cells to adhere to the substrate, we applied an immobilization technique to improve H₂ production capacity of this strain. We examined the basic properties of immobilization in Ca²⁺-alginate films in response to the production of H₂ of the Calothrix 336/3 strain and as reference strains we used a model organism Anabaena PCC 7120 and its uptake hydrogenase mutant, ΔhupL, that allow us to compare the responses of different strains to alginate entrapment. Immobilization of the Calothrix 336/3 and ΔhupL mutant cells in Ca²⁺-alginate resulted in prolonged H₂ production over several cycles. Immobilization of the Calothrix 336/3 cells was most successful and production of H₂ could be measured even after 40 days after immobilization.     

Seasonal variation in trophic structure and restoration effects in a deep perialpine lake (Lake Lugano,Switzerland and Italy)

Using monitoring data from the South Basin of Lake Lugano (Switzerland and Italy), we examined seasonal responses of phytoplankton and herbivorous zooplankton biomass to nearly three decades (1989–2017) of phosphorus (P) management to ask: [1] what is the trophic structure of the lake, [2] whether trophic structure and the effects of nutrient management varied seasonally, and [3] what are the implications of the existent trophic structure for the restoration of the lake. Trophic structure varied seasonally, including a structure consistent with strong consumer control (exploitation food chain) in spring and fall, and an unexpected structure in summer, characterized by a negative correlation between phytoplankton biomass and phosphorus. This structure was explained by accumulation of inedible phytoplankton (mainly cyanobacteria) at low P concentrations. Owing to a lack of apparent resource (P) control, P-management had no detectable effects on phytoplankton biomass. The trophic structures identified in the lake provides explanations for this lack of response to P-management and for the differences between the responses of the South Basin of Lake Lugano and other perialpine lakes. Based on the results, lake restoration practice would benefit from a greater understanding and an increased ability to predict trophic structure within and across lakes.     

Zooplankton-phytoplankton interactions in Green Bay,Lake Michigan: Lower food web responses to biological invasions

As the largest freshwater estuary in the Laurentian Great Lakes, Green Bay, Lake Michigan (USA) is an important ecosystem presenting both challenges and opportunities for investigating changes in the face of multiple anthropogenic stressors. We collected new data from 2000 to 2007 to assess changes in lower food web interactions after establishment of invasive species (Bythotrephes longimanus and Morone americana in 1988 and Dreissena polymorpha in 1993) and nutrient reductions (1990s). Phytoplankton and zooplankton biomass and composition, as well as primary productivity and zooplankton community grazing rates, were determined along the previously well-studied trophic gradient from the shallow Lower bay to the stratified, open-water Middle bay. A clear trophic gradient still occurred during 2000–2007, with higher nutrients, phytoplankton and zooplankton in Lower bay compared to Middle bay. Phytoplankton abundance and cyanobacteria dominance increased significantly compared to earlier studies. However, integrated primary productivity did not change significantly at either Lower or Middle bay. Zooplankton standing stock decreased in Lower bay, driven primarily by reductions of bosminids, chydorids, and cyclopoid copepods, but did not change in Middle bay. Zooplankton community grazing rates did not change significantly, but shifts in magnitude and seasonality of net phytoplankton growth rates are consistent with increased phytoplankton standing stocks. Changes in zooplankton composition indicate increased predation by invertebrates and decreased fish predation. Shifts in both bottom-up and top-down factors have occurred, with Lower and Middle bay regions more eutrophic and similar to each other as a result of changes in this highly productive Great Lakes embayment.     

Manipulation and Control of Micro-Organic Matter in Architecture

Steve Pike looks to a future in which architects will work alongside microbiologists and mycologists, in much the same way as they now engage with a team of engineering consultants. He explains how, with the merging of the design studio and laboratory, the manipulation and control of micro-organisms themselves have to take precedence in any successful design and production process. Copyright © 2008 John Wiley & Sons, Ltd.