The optimal growth conditions for the biomass production of Isochrysis galbana and the effects that phosphorus, Zn2+, CO2, and light intensity have on the biochemical composition of Isochrysis galbana and the activity of extracellular CA

The effects of phosphorus, Zn²⁺, CO₂, and light intensity on growth, biochemical composition, and the activity of extracellular carbonic anhydrase (CA) in Isochrysis galbana were investigated. A significant change was observed when the concentration of phosphorus in the medium was increased from 5 μmol/L to 1000 μmol/L affecting I. galbana’s cell density, biochemical composition, and the activity of extracellular CA. Phosphorous concentration of 50 μmol/L to 500 μmol/L was optimal for this microalgae. The Zn²⁺ concentration at 10 μmol/L was essential to maintain optimal growth of the cells, but a higher concentration of Zn²⁺ (≥ 1000 μmol/L) inhibited the growth of I. galbana. High CO₂ concentrations (43.75 mL/L) significantly increased the cell densities compared to low CO₂ concentrations (0.35 mL/L). However, the activity of extracellular CA decreased significantly with an increasing concentration of CO₂. The activity of extracellular CA at a CO₂ concentration of 43.75 mL/L was approximately 1/6 of the activity when the CO₂ concentration was at 0.35 mL/L CO₂. Light intensity from 4.0 mW/cm² to 5.6 mW/cm² was beneficial for the growth, biochemical composition and the activity of extracellular CA. The lower and higher light intensity was restrictive for growth and changed its biochemical composition and the activity of extracellular CA. These results indicate that phosphorus, Zn²⁺, CO₂, and light intensity are important factors that impact growth, biochemical composition and the activity of extracellular CA in I. galbana.     

Effect of irradiation intensity on cell growth and kalata B1 accumulation in <Emphasis Type="Italic">Oldenlandia affinis</Emphasis> cultures

Light irradiation had remarkable effects on callus growth of Oldenlandia affinis with an optimum intensity of 35 μmol m⁻² s⁻¹. Biosynthesis of kalata B1, the main cyclic peptide in O. affinis, was induced and triggered with rising irradiation intensities. The highest concentration of kalata B1, 0.49 mg g⁻¹ DW characterised by the maximum productivity of 3.88 μg per litre and day was analysed at 120 μmol m⁻² s⁻¹, although callus growth was repressed. The light saturation point was established to be 35 μmol m⁻² s⁻¹, where kalata B1 productivity was in a similar order (3.41 μg per day) due to the higher growth index. O. affinis suspension cultures were shown to accumulate comparable specific kalata B1 concentrations in a delayed growth associated production pattern. These were dependent on irradiation intensity (0.16 mg g⁻¹ at 2 μmol m⁻² s⁻¹; 0.28 mg g⁻¹ at 35 μmol m⁻² s⁻¹). The batch cultivation process resulted in a maximum productivity of 27.30 μg per litre and day with culture doubling times of 1.16 d⁻¹. Submers operation represented a 8-fold product enhancement compared to callus cultivation.     

Comparing the response of Antarctic,tropical and temperate microalgae to ultraviolet radiation (UVR) stress

The response of Antarctic, tropical and temperate microalgae of similar taxonomic grouping to ultraviolet radiation (UVR) stress was compared based on their growth and fatty acid profiles. Microalgae of similar taxa from the Antarctic (Chlamydomonas UMACC 229, Chlorella UMACC 237 and Navicula UMACC 231), tropical (Chlamydomonas augustae UMACC 246, Chlorella vulgaris UMACC 001 and Amphiprora UMACC 259) and temperate (Chlamydomonas augustae UMACC 247, Chlorella vulgaris UMACC 248 and Navicula incerta UMACC 249) regions were exposed to different UVR conditions. The cultures were exposed to the following conditions: PAR (42 μmol photons m⁻² s⁻¹), PAR + UVA (854 μW cm⁻²) and PAR + UVA + UVB (117 μW cm⁻²). The cultures were subjected to UVA doses of 46.1, 92.2 and 184.4 J cm⁻² and UVB doses of 6.3, 12.6 and 25.2 J cm⁻² by varying the duration of their exposure (1.5, 3 and 6 h) to UVR during the light period (12:12 h light-dark cycle). UVA did not affect the growth of the microalgae, even at the highest dose. In contrast, growth was adversely affected by UVB, especially at the highest dose. The dose that caused 50% inhibition (ID₅₀) in growth was used to assess the sensitivity of the microalgae to UVB. Sensitivity of the microalgae to UVB was species-dependent and also dependent on their biogeographic origin. Of the nine microalgae, the Antarctic Chlorella was most tolerant to UVB stress (ID₅₀ = 21.0 J cm⁻²). Except for this Chlorella, the percentage of polyunsaturated fatty acids of the microalgae decreased in response to high doses of UVB. Fatty acid profile is a useful biomarker for UVB stress for some microalgae. Presented at the 6th Meeting of the Asian Pacific Society of Applied Phycology, Manila, Philippines.     

Cell growth and nutritive value of the tropical benthic diatom, <Emphasis Type="Italic">Amphora</Emphasis> sp., at varying levels of nutrients and light intensity,and different culture locations

Two series of experiments were conducted to determine suitable growth factors for the mass propagation of the local algal isolate Amphora sp. A higher growth rate of 0.2 doubling (μ) day⁻¹ was attained at a lower photosynthetic photon flux density (PPFD; 11.4 μmol photon m⁻²s⁻¹) compared to cultures exposed to higher levels of PPFD (16.1 μmol photon m⁻²s⁻¹, −0.1 μ day ⁻¹; 31.3 μmol photon m⁻²s⁻¹, 0.0 μ day⁻¹). Cultures located inside the laboratory had a significantly higher cell density (133 × 10⁴ cells cm⁻²) and growth rate (0.3 μ day⁻¹) compared to those located outdoors (100 × 10⁴ cells cm⁻², 0.2 μ day⁻¹). A comparison of nutrient medium across two locations showed that lipid content was significantly higher in cultures enriched with F/2MTM (macronutrients + trace metals) and F/2MV (macronutrients + vitamins). Saturated fatty acids were also present in high concentrations in cultures enriched with F/2M (macronutrients only). Significantly higher amounts of saturated fatty acids were observed in cultures located outdoors (33.1%) compared to those located indoors (26.6%). The protein, carbohydrates and n-6 fatty acid content of Amphora sp. were influenced by the location and enrichment of the cultures. This study has identified growth conditions for mass culture of Amphora sp. and determined biochemical composition under those culture conditions. Presented at the 6th Meeting of the Asian Pacific Society of Applied Phycology, Manila, Philippines.     

Role of Lys281 in the <Emphasis Type="Italic">Dunaliella salina</Emphasis> (6-4) Photolyase Reaction

His³⁵⁴ and His³⁵⁸, two highly conserved histidines in Xenopus laevis (6-4) photolyase [equivalent to His⁴⁰¹ and His⁴⁰⁵, in Dunaliella salina (6-4) photolyase], are critical for photoreactivation. They act as a base and an acid, respectively. However, the remaining high repair activity when the pH value is higher than the pKa of histidine suggests the involvement of other basic amino acids in photoreactivation. According to the results of in vivo enzyme assay and three-dimension structural model of Dunaliella salina (6-4) photolyase we hypothesized that Lys²⁸¹ might be involved in the photoreactivation over the pH range from 10.0 to 11.0. To test this, we generated two mutant forms of the (6-4) photolyase, K281G and K281R mutant, by overlap extension polymerase chain reaction, and performed the enzyme assay with these mutants. From these results we conclude that the Lys²⁸¹, which is highly conserved in (6-4) photolyases, participates in the photoreactivation and acts as an acid to donate a proton to His⁴⁰¹ when the environmental pH is higher than the pKa value of histidine.     

Improvement of milbemycin-producing <Emphasis Type="Italic">Streptomyces bingchenggensis</Emphasis> by rational screening of ultraviolet- and chemically induced mutants

Milbemycin antibiotics are produced by Streptomyces hygroscopicus subsp. aureolacrimosus and a newly isolated Streptomyces bingchenggensis, respectively. According to the biosynthetic pathway of milbemycins generated by S. hygroscopicus subsp. aureolacrimosus, a rational screening procedure with UV irradiation and N-methyl-N′-nitroso-N-nitrosoguanidine (NTG) mutation was performed to obtain high milbemycin-producing S. bingchenggensis. Aminoacetic acid (Glycine)-resistant mutants (AA^r), propionate-resistant mutants (PRP^r), streptomycin-resistant mutants (STR^r) and 2-deoxy-d-glucose-resistant mutants (DOG^r) were selected successively. A strain S. bingchenggensis BC-109-6 with AA^r, PRPr, STR^r and DOG^r was obtained and its production of milbemycin A3 and A4 reached 1,450 μg/ml, which was 80% higher than that of the ancestral strain S. bingchenggensis BC-101-4. The subculture experiments indicated that the hereditary characteristic of high productivity of S. bingchenggensis BC-109-6 was stable. The production of milbemycin A3 and A4 by S. bingchenggensis BC-109-6 in a 50-l fermentor could reach 1,380 μg/ml after 360 h batch fermentation.     

Phenols,proline and low-molecular thiol levels in pea (<Emphasis Type="Italic">Pisum sativum</Emphasis>) plants respond differently toward prolonged exposure to ultraviolet-B and ultraviolet-C radiations

Pea (Pisum sativum L.) seedlings were exposed to low, moderate, and high regimes of ultraviolet-B (UV-B) (ld-B 4.4, md-B 13.3, and hd-B 26.5 kJ m⁻² day⁻¹), or ultraviolet-C (UV-C) (ld-C 0.1, md-C 0.3, and hd-C 0.6 kJ m⁻² day⁻¹) radiations. Concentrations of total phenols, free proline, and low-molecular thiol groups were determined in the last formed (young) and older leaves after irradiation for 7, 10 or 14 consecutive days. Shoot length and weight did not change markedly after 14 days of ld-B and ld-C, but reduced substantially after moderate and high regimes of both UV-B and UV-C. Proline decreased upon high doses of irradiation, while in ld-B treated plants, by contrast, an increase was observed. The reduction in total phenols and thiols was stronger after hd-B than after hd-C irradiations, although an induction was found in ld-B treated plants. In contrast to ld-B, ld-C regime led mainly to reductions or insignificant changes in proline, phenols, and thiols. Therefore, the stress-protection mechanisms are different between low UV-B and UV-C irradiation regimes in regard to proline, phenols, and thiols.     

In vitro percutaneous absorption of boron as boric acid, borax, and disodium octaborate tetrahydrate in human skin: a summary

Literature from the first half of this century reports concern for toxicity from topical use of boric acid, but assessment of percutaneous absorption has been impaired by lack of analytical sensitivity. Analytical methods in this study included inductively coupled plasmamass spectrometry which now allows quantitation of percutaneous absorption of¹⁰B in¹⁰B-enriched boric acid, borax and disodium octaborate tetrahydrate (DOT) in biological matrices. In vitro human skin percent doses of boric acid absorbed were 1.2 for a 0.05% solution, 0.28 for a 0.5% solution, and 0.70 for a 5.0% solution. These absorption amounts translated into flux values of, respectively, 0.25, 0.58, and 14.58 μg/cm²/h, and permeability constants (K _p ) of 5.0 x 10^-4, 1.2 x 10^-4, and 2.9 x 10^-4 cm/h for the 0.05%, 0.5%, and 5.0% solutions. The above in vitro doses were at infinite, 1000 μL/cm² volume. At 2 μL/cm² (the in vivo dosing volume), flux decreased some 200-fold to 0.07 μg/cm²/h andK _p of 1.4 x 10^-6 cm/h, while percent dose absorbed was 1.75%. Borax dosed at 5.0%/1000 μL/cm² had 0.41 percent dose absorbed, flux at 8.5 μg/cm²/h, andK _p was 1.7 x 10^-4 cm/h. Disodium octaborate tetrahydrate (DOT) dosed at 10%/1000 μL/cm² was 0.19 percent dose absorbed, flux at 7.9 μg/cm²/h, andK _p was 0.8 x ICH cm/h. These in vitro results from infinite doses (1000 μL/cm²) were a 1000-fold greater than those obtained in the companion in vivo study. The results from the finite (2 μL/cm²) dosing were closer (10-fold difference) to the in vivo results. General application of infinite dose percutaneous absorption values for risk assessment is questioned by these results.     

Minimal levels of cold-adaptation in postsynaptic currents of a subantarctic teleost, <Emphasis Type="Italic">Notothenia rossii</Emphasis> (Perciformes: Notothenioidei: Nototheniidae)

As a part of the ICEFISH04 project on the RVIB Nathaniel B. Palmer, miniature end plate currents (MEPCs) were recorded from the extraocular muscles of Notothenia rossii captured at King Edward Point, South Georgia. A total of 1,176 MEPCs were recorded from the inferior oblique extraocular muscles of four specimens, over a temperature range of 1–12°C. The MEPCs were normal in form, with a rapid quasi-linear increase in inward current (typically <500 μs), followed by a slower exponential decay of the inward current to baseline. Exponential decay rates were calculated for individual MEPCs by linear regression of the log-transformed data, and converted to exponential time constants (τ). Only those MEPCs that fit the exponential model well, with r ² ≥ 0.95 (or in some cases r ² ≥ 0.99) were used for further calculations. At temperatures between 1 and 2°C, τ ranged from about 2,000 to 4,000 μs, similar to values extrapolated for temperate teleosts at the same temperature, but significantly longer than τ from MEPCs of high-latitude Antarctic nototheniids. Between 11 and 12°C, τ values for the N. rossii MEPCS were mainly between 1,100 and 1,700 μs, giving a Q ₁₀ of 2.05. An Arrhenius plot and linear regression were used to describe the effect of changing temperature on the decay phase of the N. rossii MEPCs: −ln τ = 27.887−6078/K, yielding an Arrhenius temperature coefficient (μ or apparent E _a) of −50.5 ± 2.9 (95% CL) kJ mol⁻¹ deg⁻¹. When compared with other nototheniids, these results showed that the neuromuscular junctions of N. rossii are compensated for low temperature, but not to the same degree as those of high Antarctic species. The ICEFISH Cruise (International Collaborative Expedition to collect and study Fish Indigenous to Sub-antarctic Habitats) was conducted on board the RVIB Nathaniel B. Palmer in May to July 2004. For further information, please visit .     

Aeration volume and photosynthetic photon flux affect cell growth and secondary metabolite contents in bioreactor cultures ofMorinda citrifolia

To improve their growth and secondary metabolite production, we culturedMorinda citrifolia leaf cells for 3 weeks in bioreactors with different aeration volumes (0.05, 0.1, 0.2, or 0.3 vvm; or 0.05/0.1/0.2/0.3 vvm, as increased at 5-d interval), and photosynthetic photon fluxes (PPF; 0, 15, 30, or 45 μ,moL m^-2 s^-1). Cell growth was greatest (15.6 g L^-1 dry weight) at 0.3 vvm whereas the accumulation of secondary metabolites (total anthraquinones, phenolics, and flavonoids) was maximized at 0.1 vvm. A PPF of 15 μmoLm^-2 s^-1 accelerated the accumulation of both cell biomass and metabolites. Dark-culturing suppressed cell growth, while a high PPF (45 μmoLm^-2 s^-1) inhibited metabolite biosynthesis. Further studies are required to understand the reason for differences in the effect of light on cell growth and secondary metabolite contents inM. citrifolia cell cultures.     

Changes in the human nuclear chromatin induced by ultra wideband pulse irradiation

The effects of ultra wideband pulse radiation on human cells were investigated. The density of the flow of energy on the surface of irradiated object varied from 10⁻⁶ to 10⁻² W/cm² with exposure of 10 s. It was shown that heterochromatin granule quantity in cell nuclei increased under the influence of radiation from 10⁻⁴ to 10⁻² W/cm². In some intervals the effect increased with irradiation dose. At irradiation intensity 10⁻³ W/cm² the process of heterochromatin granule formation was fully reversible after 2 h of recovery; at intensity 10⁻² W/cm² the reversion of irradiation effects was not full. The data obtained indicated the strong biological activity of ultra wideband ultra short pulse radiation.     

In Vitro Percutaneous Permeation and Skin Accumulation of Finasteride Using Vesicular Ethosomal Carriers

In order to develop a novel transdermal drug delivery system that facilitates the skin permeation of finasteride encapsulated in novel lipid-based vesicular carriers (ethosomes)finasteride ethosomes were constructed and the morphological characteristics were studied by transmission electron microscopy. The particle size, zeta potential and the entrapment capacity of ethosome were also determined. In contrast to liposomes ethosomes were of more condensed vesicular structure and they were found to be oppositely charged. Ethosomes were found to be more efficient delivery carriers with high encapsulation capacities. In vitro percutaneous permeation experiments demonstrated that the permeation of finasteride through human cadaver skin was significantly increased when ethosomes were used. The finasteride transdermal fluxes from ethosomes containing formulation (1.34 ± 0.11 μg/cm²/h) were 7.4, 3.2 and 2.6 times higher than that of finasteride from aqueous solution, conventional liposomes and hydroethanolic solution respectively (P < 0.01).Furthermore, ethosomes produced a significant (P < 0.01) finasteride accumulation in the skin, especially in deeper layers, for instance in dermis it reached to 18.2 ± 1.8 μg/cm². In contrast, the accumulation of finasteride in the dermis was only 2.8 ± 1.3 μg/cm² with liposome formulation. The study demonstrated that ethosomes are promising vesicular carriers for enhancing percutaneous absorption of finasteride.     

Properties of native and hydrophobic laccases immobilized in the liquid-crystalline cubic phase on electrodes

Both native Trametes hirsuta laccase and the same laccase modified with palmytic chains to turn it more hydrophobic were prepared and studied with cyclic voltammetry and Raman spectroscopy. Native laccase immobilized in the monoolein cubic phase was characterized with resonance Raman spectroscopy, which demonstrated that the structure at the “blue” copper site of the protein remained intact. The diamond-type monoolein cubic phase prevents denaturation of enzymes on the electrode surface and provides contact of the enzyme with the electrode either directly or through the mediation by electroactive probes. Direct electron transfer for both laccases incorporated into a lyotropic liquid crystal was obtained under anaerobic conditions, whereas bioelectrocatalytic activity was shown only for the native enzyme. The differences in electrochemical behavior of native and hydrophobic laccase as well as possible mechanisms of direct and mediated electron transfers are discussed. The Michaelis constant for 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) diammonium salt (ABTS²⁻), K _M^app, and the maximal current, I _max, for the native enzyme immobilized onto the electrode were estimated to be 0.24 mM, and 5.3 μA, respectively. The maximal current density and the efficiency of the catalysis, I _max/K _M^app, were found to be 73 μA cm⁻² and 208.2 μA cm⁻² mM⁻¹, respectively, and indicated a high efficiency of oxygen electroreduction by the enzyme in the presence of ABTS²⁻ in the cubic-phase environment. Rate constants were calculated to be 7.5 × 10⁴ and 3.6 × 10⁴ M⁻¹ s⁻¹ for native and hydrophobic laccase, respectively.     

Mutagenic and Genotoxic Effects of <Emphasis Type="Italic">cis</Emphasis>-(Dichloro)tetraammineruthenium(III) Chloride on Human Peripheral Blood Lymphocytes

Chemotherapeutic agents play an important role in cancer treatment mostly due their systemic action on human organism allowing access to liquid tumors and even metastases. Among these drugs, ruthenium compounds have been showing promising results to treat tumors and represent an important development of new antitumor therapy. This study presents the evaluation of cis-(dichloro)tetraammineruthenium(III) chloride, cis-[RuCl₂(NH₃)₄]Cl, genotoxic effects using human peripheral blood lymphocytes cultured in vitro. Mitotic index (MI), chromosome aberrations (CA), and DNA damage using the comet assay were analyzed. MI in human peripheral blood lymphocyte cultures treated with 1, 10, 100, and 1,000 μg mL⁻¹ cis-[RuCl₂(NH₃)₄]Cl were 5.9%, 4.6%, 3.9%, and 0%, respectively. Doxorubicin chloridate was used as the positive control. CA derived from 1, 10, and 100 μg mL⁻¹ concentrations were defined as spontaneous when compared with the negative control, and at the concentration of 1,000 μg mL⁻¹, the cell cycle was inhibited (IM = 0%). Results obtained for the comet assay using cis-[RuCl₂(NH₃)₄]Cl suggest that this compound has no genotoxic activity against cultured human peripheral blood lymphocytes.     

Inhibition of aggregation by light in the cellular slime mold Dictyostelium discoideum

Aggregation of Dictyostelium amoebae is inhibited by light. White light intensities 10² W · cm^-2 cause an inhibition which reaches a saturation at 2 · 10³ W · cm^-2. The action spectrum, based on photon fluence-response curves, shows a major peak around 405 nm and extends through most of the visible spectrum with a secondary maximum at about 530 nm. The action spectrum of the inhibition of aggregation resembles the action spectrum of accumulations of amoebae in light traps and the action spectrum of photodispersal from light traps; it does not resemble the action spectrum of phototaxis in pseudoplasmodia.     

Enhanced iturin A production by <Emphasis Type="Italic">Bacillus subtilis</Emphasis> and its effect on suppression of the plant pathogen <Emphasis Type="Italic">Rhizoctonia solani</Emphasis>

The behavior of Streptomyces peucetius var. caesius N47 was studied in a glucose limited chemostat with a complex cultivation medium. The steady-state study yielded the characteristic constants μ _max over 0.10 h⁻¹, Y _XS 0.536 g g⁻¹, and m_S 0.54 mg g⁻¹ h⁻¹. The product of secondary metabolism, ɛ-rhodomycinone, was produced with characteristics Y _PX 12.99 mg g⁻¹ and m _P 1.20 mg g⁻¹ h⁻¹. Significant correlations were found for phosphate and glucose consumption with biomass and ɛ-rhodomycinone production. Metabolic flux analysis was conducted to estimate intracellular fluxes at different dilution rates. TCA, PPP, and shikimate pathway fluxes exhibited bigger values with production than with growth. Environmental perturbation experiments with temperature, airflow, and pH changes on a steady-state chemostat implied that an elevation of pH could be the most effective way to shift the cells from growing to producing, as the pH change induced the biggest transient increase to the calculated ɛ-rhodomycinone flux.     

Heavy metal resistant <Emphasis Type="Italic">Distigma proteus</Emphasis> (Euglenophyta) isolated from industrial effluents and its possible role in bioremediation of contaminated wastewaters

Summary The alga, Distigma proteus, isolated from industrial wastewater showed tolerance against Cd²⁺ (8.0 μg/ml), Cr⁶⁺ (12 μg/ml), Pb²⁺ (15 μg/ml) and Cu²⁺ (10 μg/ml). The metal ions slowed down the growth of the organism after 4–5 days of exposure. The reduction in cell population was 90% for Cu²⁺, 84% for Cd²⁺, 71% for Cr⁶⁺, and 63% for Pb²⁺ after 8 days of metal stress. The order of resistance to heavy metal, in terms of reduction in the cellular population, was Cu²⁺ > Cd²⁺ > Cr⁶⁺ > Pb²⁺. Chromium- and cadmium-processing capabilities of the alga were worked out for its potential use as a bioremediator of wastewater. The reduction in the amount of Cr⁶⁺ after 2, 4, 6 and 8 days of algal culture containing 5.0 μg Cr⁶⁺ ml⁻¹ of culture medium was 77, 85, 92 and 97%, respectively. Distigma could also remove 48% Cd²⁺after 2 days, 68% after 4 days, 80% after 6 days and 90% after 8 days from the medium. The heavy metal uptake ability of Distigma can be exploited for metal detoxification and environmental clean-up operations.     

Destruction of Deinococcus geothermalis biofilm by photocatalytic ALD and sol-gel TiO2 surfaces

The aim of the present work was to explore possibilities of photocatalytic TiO₂ coating for reducing biofilms on non-living surfaces. The model organism, Deinococcus geothermalis, known to initiate growth of durable, colored biofilms on machine surfaces in the paper industry, was allowed to form biofilms on stainless steel, glass and TiO₂ film coated glass or titanium. Field emission electron microscopy revealed that the cells in the biofilm formed at 45°C under vigorous shaking were connected to the surface by means of numerous adhesion threads of 0.1--0.3 μm in length. Adjacent cells were connected to one another by threads of 0.5--1 μm in length. An ultrastructural analysis gave no indication for the involvement of amorphous extracellular materials (e.g., slime) in the biofilm. When biofilms on photocatalytic TiO₂ surfaces, submerged in water, were exposed to 20 W h m⁻² of 360 nm light, both kinds of adhesion threads were completely destroyed and the D. geothermalis cells were extensively removed (from >10⁷ down to below 10⁶ cells cm⁻²). TiO₂ films prepared by the sol-gel technique were slightly more effective than those prepared by the ALD technique. Doping of the TiO₂ with sulfur did not enhance its biofilm-destroying capacity. The results show that photocatalytic TiO₂ surfaces have potential as a self-cleaning technology for warm water using industries.     

Strong-light response of Micrasterias thomasiana Archer

Prostrate cells of Micrasterias thomasiana Archer were irradiated from above with intensive blue light. Many of the cells reacted by rising to a profile position. During a period of 15 to 90 min the response is linearly dependent on the duration of irradiation, inferred from the number of rising cells. In a range from 10 to 30 mol m^-2 s^-1 (equalling 2.7–8.0 W m^-2 at a wavelength of 450 nm) and for an irradiation time of 30 min, the rising reaction was linearly dependent on the quantum flux density. Choosing 30 min irradiation time and a quantum flux density of 30 mol m^-2 s^-1, the reactive number of rising cells was employed in establishing an action spectrum. As a result of this, a flavin is postulated as the light-percepting pigment in the reaction, whereas chlorophylls do not appear to be involved. The rising reaction can be distinguished from other light-induced movements as a strong-light response, resembling in this respect the movement of chloroplasts within cells. The different sensitivity of individual cells and the importance of this strong-light response for the algal cells is discussed.