The effects of copper and zinc on growth of the fouling diatoms amphora and amphiprora

Copper and zinc salts act synergistically and have inhibitory effects on the growth of the diatoms Amphora coffeaeformis and Amphiprora hyalina. The concentrations required to cause a significant reduction in growth yields indicate that the isolates of the two species used are copper and zinc tolerant. Some growth stimulation was found in lower concentrations of the two metals. Cellular levels generally increased with increasing concentrations in the external medium, resulting in increased growth inhibition. Growth yields and cellular copper concentrations were found to be related to calculated cupric ion activities in the medium. Relative inhibitory and cellular concentrations of copper and zinc tor A. coffeaeformis and A. hyalina suggest that the latter species may be more sensitive to CuC1₂‐2HjO and more tolerant to ZnCl₂ than the former. The results suggest that inclusion of ZnO as an additional biocide in self‐polishing copolymer antifouling paints would result in more effective antifouling action.     

Protective Effect of Enzymatic Extracts from Microalgae Against DNA Damage Induced by H<Subscript>2</Subscript>O<Subscript>2</Subscript>

The enzymatic extracts from seven species of microalgae (Pediastrum duplex, Dactylococcopsis fascicularis, Halochlorococcum porphyrae, Oltmannsiellopsis unicellularis, Achnanthes longipes, Navicula sp. and Amphora coffeaeformis) collected from three habitats (freshwater, tidal pool, and coastal benthic) at Jeju Island in Korea were investigated for their antioxidant activity. Of the extracts tested, the AMG 300 L (an exo 1, 4-α-d-glucosidase) extract of P. duplex, the Viscozyme extract of Navicula sp., and the Celluclast extract of A. longipes provided the most potential as antioxidants. Meanwhile, the Termamyl extract of P. duplex in an H₂O₂ scavenging assay exhibited an approximate 60% scavenging effect. In this study, we report that the DNA damage inhibitory effects of P. duplex (Termamyl extract) and D. fascicularis (Kojizyme extract) were nearly 80% and 69% respectively at a concentration of 100 μg/ml. Thus, it is suggested that the microalgae tested in this study yield promising DNA damage inhibitory properties on mouse lymphoma L 5178 cells that are treated with H₂O₂. Therefore, microalgae such as P. duplex may be an excellent source of naturally occurring antioxidant compounds with potent DNA damage inhibition potential.     

Adhesion of the marine fouling diatom amphora coffeaeformis to non‐solid gel surfaces

Diatom adhesion to different gel surfaces was tested under different shear conditions, using the fouling marine diatom Amphora coffeaeformis as test organism. Four polymers were selected to obtain a test matrix containing gels with different surface charge as well as different surface energies, viz. agarose, alginate, chitosan and chemically modified polyvinylalcohol (PVA‐SbQ). Three experimental systems were applied to obtain different shear rates. Experimental system 1 consisted of gels cast in a cell culturing well plate for comparing initial adhesion as well as long term biofilm development in the absence of shear. In experimental system 2, microscope slide based test surfaces were tested in aquaria under low shear conditions. A rotating annular biofilm reactor was used to obtain high and controlled shear rates. At high shear rates A. coffeaeformis cells adhered better to the charged polymer gels (alginate and chitosan) than to the low charged polymer gels (agarose and PVA‐SbQ). In the system where shear was absent A. coffeaeformis cells developed a biofilm on agarose equivalent to the charged polymer gels, while adhesion to PVA‐SbQ remained low at all shear rates. It is concluded that non‐solid surfaces did not represent an obstacle to settling and growth of this organism. As observed for solid surfaces, low charge density led to reduced attachment, particularly at high shear.     

Inhibitory Effects of Some Spice and Herb Extracts Against Arcobacter butzleri, A. cryaerophilus, and A. skirrowii

Seventeen spice and medicinal plant extracts (methanol and chloroform) were assayed for their antimicrobial activity against Arcobacter butzleri, A. cryaerophilus, and A. skirrowii. In general, all of the tested extracts were able, to a different extent, to inhibit the growth of the selected Arcobacter species. Cinnamon, bearberry, chamomile, sage and rosemary extracts showed strong antimicrobial activity toward arcobacter strains tested. Overall, the methanol extracts showed better activity than the chloroform extracts (P < 0.05); however, enhanced antibacterial activity of chloroform extracts of cinnamon and rosemary has been observed in comparison with their methanol counterparts. The inhibitory dose of the most active extracts (the diameter of zone of inhibition ≥ 20 mm) was determined using the disc-diffusion method as well.     

A Potent Phytotoxic Substance in Aglaia odorata Lour.

Aglaia odorata Lour . (Meliaceae) was found to have very strong allelopathic activity and a bioherbicide PORGANIC^? was developed from its leaf extracts. However, the phytotoxic substances causing the strong allelopathic activity of the plants have not yet been determined. Therefore, we investigated allelopathic properties and phytotoxic substances in A. odorata. Aqueous EtOH extracts of A. odorata leaves inhibited root and shoot growth of garden cress (Lepidum sativum), lettuce (Lactuca sativa), alfalfa (Medicago sativa), timothy (Phleum pratense), ryegrass (Lolium multiflorum), and Echinochloa crus‐galli with the extract concentration‐dependent manner. The extracts were then purified and a major phytotoxic substance with allelopathic activity was isolated and identified by spectral data as rocaglaol. Rocaglaol inhibited the growth of garden cress and E. crus‐galli at concentrations > 0.3 and 0.03 μm , respectively. The concentrations required for 50% inhibition ranged from 0.09 to 2.5 μm . The inhibitory activity of rocaglaol on the weed species, E. crus‐galli, was much greater than that of abscisic acid. These results suggest that rocaglaol may be a major contributor to the allelopathic effect of A. odorata and bioherbicide PORGANIC^?.     

Phytoplankton growth under temperature stress: Laboratory studies using two diatoms from a tropical coastal power station site

(1) The paper reports results of laboratory studies on growth rates at elevated temperatures of two diatoms (Chaetoceros wighami and Amphora coffeaeformis) isolated from the intake and outfall sites of a coastal power station on the east coast of India. (2) Temperature exposures consisted of acute and chronic treatments to simulate condenser transit and prolonged thermal plume entrainment. (3) The results showed that the various temperature zones presented by cooling water circuit of the power station would permit diatom growth, with growth rates that are marginally different form those at average ambient sea temperature. (4) Fundamental differences in the response of different diatom species to temperature stress result in the abundance of the more tolerant species such as A. coffeaeformis which dominate in an elevated temperature zone, such as that offered by the discharge canal of the power station.     

外来红树植物拉关木对乡土种桐花树和正红树的化感作用研究

为了探究外来红树植物拉关木对乡土红树植物的化感作用,该研究观察了不同浓度(0.1、0.3、0.5g·mL~(-1))的拉关木根、叶水浸提液对乡土红树植物桐花树和正红树的胚轴(种子)萌发、幼苗生长及叶片抗氧化酶活性的影响。结果表明:(1)拉关木水浸提液对桐花树种子的成苗率、萌发指数和根长均存在抑制作用,其中对根长的抑制作用随水浸提液浓度的提高而增强。(2)根水浸提液对桐花树幼苗的根长、苗高、生物量等生长指标的影响总体上均表现为低浓度促进,高浓度抑制。(3)拉关木水浸提液对正红树胚轴的萌发率、萌发指数、生长指标均表现为促进作用,且根水浸提液0.1、0.3 g·mL~(-1)处理组的芽长以及根、叶水浸提液0.1、0.3 g·mL~(-1)处理组的生物量显著大于对照组;拉关木水浸提液对正红树幼苗的生物量也表现为促进作用。(4)抗性生理方面,随着拉关木水浸提液浓度的升高,桐花树和正红树幼苗SOD活性降低,正红树幼苗POD活性在根水浸提液0.3 g·mL~(-1)和叶水浸提液0.1 g·mL~(-1)处理组显著高于对照组。以上结果表明,不同乡土植物对拉关木化感作用的敏感性不同,拉关木水浸提液抑制了桐花树的生长,而对正红树的生长则表现出一定程度的促进作用。     

米槁-绿壳砂林药间作系统可行性

为了充分利用米槁林下空间,从化感效应的角度研究人工米槁林下土壤水浸提液对绿壳砂生长状况的影响,探索米槁与绿壳砂建立间作经营系统的可能性。以绿壳砂为受体,米槁根际土壤与林间土壤水浸提液为供试液,设置6个浓度0、0.5、1、5、10、50 mg/mL的水浸提液处理绿壳砂,对绿壳砂种子萌发和幼苗生理生化指标进行测定,以此探讨米槁根际土壤与林间土壤水浸提液对绿壳砂生长的影响。结果表明:米槁两种土壤水浸提液对绿壳砂种子的萌发大体上呈现低浓度促进高浓度抑制的浓度效应,但随着浓度的变化,差异不显著;米槁林间土壤水浸提液对绿壳砂幼苗的总生物量及苗高都表现出显著的促进作用,呈先增加后缓慢减小的趋势,根际土壤水浸提液则在高浓度时表现出抑制作用。从化感效应综合指数看出,2种水浸提液对可溶性蛋白质含量、游离脯氨酸(Pro)含量、土壤脲酶(S-UE)活性表现为抑制作用,其余都为促进作用,且林间土壤的促进效果强于根际土壤。应用GC-MS从米槁根际土壤与林间土壤中分别鉴定出18种化合物,虽含有酚酸和烷烃类等化感物质,但在一定浓度范围内,对绿壳砂种子萌发、幼苗生长没有明显的抑制作用,且在米槁林土水浸提液处理下表现出更强的适应性。因此,在米槁林下套种绿壳砂时采取幼苗移栽法,构建米槁-绿壳砂林药间作经营体系具有一定可行性。     

Fungicidal activity of Prosopis africana and Anogeissus leiocarpus aqueous extracts against leaf blight of Jatropha curcas L.

A laboratory experiment was conducted to determine the efficacies of leaf and bark aqueous extracts of two plants (Prosopis africana and Anogeissus leiocarpus) at three concentrations (50%, 100% and 150%) on Curvularia sp. isolated from Jatropha curcas L. The fungicidal potentials of the extracts were established by their inhibitory effect on the mycelial growth, sporulation and reduction of spore size of Curvularia sp. The extract of Prosopis bark gave the highest inhibitory effect followed by Anogeissus bark, Prosopis leaf and then Anogeissus leaf. Leaf and bark extracts of P. africana and A. leiocarpus compared significantly better than untreated control. The bark extracts especially of P. africana did not differ significantly from a standard check (Bentex-T, 20% Benomyl + 20% Thiram).     

Tea extracts differentially inhibit Streptococcus mutans and Streptococcus sobrinus biofilm colonization depending on the steeping temperature

Abstract

This study aimed to evaluate the effects of tea extracts on oral biofilm colonization depending on steeping temperature. S. mutans and S. sobrinus were cultured and treated with green or black tea extracts prepared under different steeping conditions. Biofilm formation, glucosyltransferase (GTF) levels, bacterial growth, and acidogenicity were evaluated. Biofilms were also assessed by gas chromatography-mass spectrometry and confocal laser scanning microscopy. All extracts with hot steeping showed higher inhibitory effects on biofilm formation and cell viability and lower GTF levels compared with those with cold steeping (p?<?0.05). Hot steeping significantly reduced bacterial growth (p?<?0.05) and maintained the pH. Catechins were only identified from hot steeping extracts. Within the limits of this study, extracts with cold steeping showed lower inhibitory effects on oral biofilms. The different effects between steeping extracts may be attributed to the difference in catechins released from tea extracts under the different steep conditions.     

Antifungal activity of some plant extracts on some pathogenic fungi

The inhibitory activity of five plant extracts viz. Artemisia absinthium L., Rumex obtusifolius L., Taraxacum officinale Weber ex Wiggers, Plantago lanceolata L. and Malva sylvestris L. were evaluated against the mycelial growth of three fungi Alternaria alternata (Fr.) Keissler, Penicillium expansum Link ex Thom. and Mucor piriformis Fisher that cause rot diseases in fruits and vegetables resulting in low yield and quality of fruits and vegetables. Results revealed that all the concentrations of plant extracts brought about significant inhibition in the mycelial growth of these pathogenic fungi. However, the highest concentration caused maximum inhibition in the mycelial growth followed by lower concentrations of plant extracts. The extract of A. absinthium leaves at highest concentration (S) proved highly effective in inhibiting the mycelial growth of all these pathogenic fungi followed by other plant extracts. These plants thus may have potential as the new natural fungicide for management of fungal rot diseases.     

GROWTH-INHIBITORS AND GROWTH-PROMOTERS IN ENTEROMORPHA COMPRESS A (CHLOROPHYTA)1

Methanol extracts from the alga Enteromorpha compressa (L.) Grev. contain substances which inhibit the elongation of Lepidium roots. Chromatographic separation of the inhibiting substances revealed that one of the inhibitory zones of the chromatograms had properties of the so-called inhibitor β. Neither abscisic acid (ABA) nor lunularic acid proved to be responsible for the growth-inhibiting property of this zone. Moreover, the extracts contain substances which promote the elongation of Avena coleoptile segments. One of these substances could be tentatively identified as indole-3-acetic acid by thin-layer and gas-liquid chromatography. (In addition to indole-3-acetic acid a second growth-promoting factor with the properties of the so-called accelerator α could be detected.)     

Effects of elevated CO2 and temperature on the growth,elemental composition,and cell size of two marine diatoms: potential implications of global climate change

Two pennate diatoms, Amphora coffeaeformis and Nitzschia ovalis, were used to evaluate potential responses to the future CO₂ and temperature increases with respect to cell-specific growth rate, elemental composition, size, population growth rate, and carrying capacity. Diatoms were subjected to four different treatments over a 2 week period (approximately 4 generations): a control (28°C and present-day CO₂, ~400 ppm), high CO₂ (28°C with high CO₂, ~750 ppm), high temperature (31°C and present-day CO₂, ~400 ppm), and greenhouse-effect treatment (31°C with high CO₂, ~750 ppm). The results indicated that both the cell-specific growth rates and the carrying capacity of A. coffeaeformis decreased at the higher temperature treatment, whereas N. ovalis did not differ among all treatments. No significant difference was found in either species’ elemental cell composition, but higher C:N and C:P ratios were observed for A. coffeaeformis and N. ovalis, respectively, in high CO₂ and greenhouse-effect treatments. Smaller cell sizes were observed for both species under the greenhouse-effect treatment, a phenomenon that could alter benthic food webs in the future.     

In vitro assessment of fungicidal activity of Ageratum conyzoides and Cybopogon flexuosus weed extracts against some phytopathogenic fungi associated with fruit rot of water melon (Citrullus lunatus (Thunb.))

The ethanolic extracts of Cybopogon flexuosus and Ageratum conyzoides were tested at concentrations of 20, 40, 60, 80, 100 and 120?mg/ml for their in vitro fungicidal activities against five phytopathogenic fungi isolated from diseased watermelon fruits. The pathogens were Fusarium verticillioides, Aspergillus flavus, Botryodiplodia theobromae, Curvularia lunata and Alternaria cucumeria – Amans as confirmed by pathogenicity tests. All isolated pathogenic fungi were significantly (p?≥?0.05) highly pathogenic with the exception of A. cucumeria which had the least significant (p?≥?0.05) pathogenicity. The inhibitory effects of the extracts increased significantly (p?≥?0.05) with increase in concentrations. Some of the concentrations reduced the mycelial growth of the pathogens to a significant (p?≥?0.05) level. Very strong fungicidal activity was produced by extracts of A. conyzoides at 100?mg/ml against all the fungi. The inhibitory effects of C. flexuosus extracts at 20, 40 and 60?mg/ml were greater than those of C. flexuosus on A. flavus, F. verticillioides and A. cucumeria. The results of the investigation indicated that plant extracts possess antifungal activity that can be exploited as an ideal treatment for future plant disease management in the control of rot of water melon.     

A quantitative bioassay for extracellular metabolites that antagonize growth of filamentous fungi,and its use with biocontrol fungi

A bioassay and an empirically derived formula were developed to quantify fungitoxic effects. This bioassay can be easily performed and objectively read, and it is suitable for low-volume samples originating from aqueous or organic solvents. The formula defines the Inhibition Index (I), a single value that incorporates both the response to concentrations of the inhibitory compound and the persistence of inhibition. Antagonistic efficacy of metabolites produced by biocontrol strains of Trichoderma spp. were measured based on inhibition of growth of Rhizoctonia solani. Although the bioassay itself was not influenced by pH or light conditions, these factors affected metabolite production or activity. Aqueous extracts from light-grown germlings of Trichoderma virens inhibited R. solani more than extracts from germlings grown in the dark. Low pH increased the inhibitory activity of extracts from T. virens. Tests of fungal strains developed for biocontrol demonstrated that the bioassay reflected their activity both in the field and in other in vitro tests. The bioassay and formula are readily adapted for use with other fungi.This revised version was published online in October 2005 with corrections to the Cover Date.     

Allelopathic activity of different plant parts of <Emphasis Type="Italic">Peganum harmala</Emphasis> L. and identification of their growth inhibitors substances

This study was conducted to evaluate the inhibitory potential of P. harmala leaf, stem and root extract on germination and growth of Avena fatua L. and Convolvulus arvensis L., as well as identification of the phytotoxic substances responsible for this activity. According to our results, the degree of toxicity of different P. harmala plant parts can be arranged in the following order: leaves > stems > roots. The two test species differed in their sensitivity to P. harmala extracts. Inhibitory effect on shoot length and seedling dry weight was more pronounced in C. arvensis, whereas higher reduction in germination, root length and total chlorophyll content occurred in A. fatua. A significant amount of water-soluble phenolic acids were found in P. harmala plant extracts. Total phenolic acids content was higher in leaf extracts when compared to that of stem or root extracts. Seven phenolic acids including gallic acid, vanillic acid, 4-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid, caffeic acid, syringic acid and ferulic acid were found in P. harmala leaf extracts. On the other hand, we identified four phenolic acids from stem (galllic acid, vanillic acid, 3,4-dihydroxybenzoic acid and caffeic acid) and root (galllic acid, 4-hydroxybenzoic acid, syringic acid and cinnamic acid) extracts. The greater number of growth inhibitors detected in the leaves might explain the stronger inhibitory activity. Overall, our results suggest that P. harmala might be used as a natural herbicide for weed control and consequently reduce dependence on synthetic herbicides.     

Allelopathic effect of Nymphaea lotus L. on growth and yield of cultivated rice around Lake Manzala (Nile Delta)

Lotus infestation of ricefields is a major cause of crop failure and decrease of grain yield in the newly reclaimed cut-off areas around lake Manzala, Egypt. This study provides insights in the allelopathic effect of Nymphaea lotus L. on rice (Oryza sativa cavr. Giza-177). Lotus rhizome extracts were inhibitory to seed germination and seedling growth of rice. The degree of inhibition was dependent on extract type and concentration. Ethanol and water extracts were more inhibitory than chloroform extracts. The phenolic fraction of ethanol extracts showed the highest inhibitory effects. In a target (rice)-neighbour (lotus) pot experiment, rice dry mass and relative growth rate were dependent on its age and on lotus rhizome density, with decreased growth at increased lotus density. Field data on infested and non-infested ricefields demonstrated a decreased leaf area index and yield in infested fields. Identification of the potential allelochemical compounds by gas chromatography/mass spectrometry revealed the presence of allelopathic phenolics in lotus rhizomes.     

The role of bacteria in the metal tolerance of the fouling diatom Amphora coffeaeformis Ag.

Components of “spent” axenic and non-axenic Amphora coffeaeformis Ag. culture media were tested for their effect on copper and tributyltin tolerance in axenic A. coffeaeformis. Growth of such algal cultures in the presence of either toxin was enhanced by the addition of enriched “spent” medium from exponentially growing non-axenic cultures. This response was seen whether or not the bacteria had been removed. It appears that bacteria or bacteria-algal interactions produce some soluble (<0.2 μm) factor which either decreases the toxicity of copper and tributyltinfluoride (TBTF) or increases the tolerance of A. coffeaeformis to these toxins.     

Production of a plasmin inhibitory substance by Scopolia japonica suspension cultures

A potent inhibitory agent against human plasmin, fibrinolytic proteinase, has been found in the extracts of callus tissue of Scopolia japonica. Effects of cultural conditions on cell growth and production of the plasmin inhibitory substance by this cell line in suspension cultures were examined in MurashigeSkoog's medium. More than l.5 mg of the inhibitor, as t-amino cyclohexane carboxylic acid, a synthetic plasmin inhibitor, were observed to accumulate per ml of medium containing 0.83 g of NH₄NO₃ and 7.6 g of KNO₃ per liter as well as suitable levels of growth hormones. Addiction of antibiotics and deformers were examined in preliminary tests for large scale cultivation. Semicontinuous culture on a small scale in a glass cylinder, was also tested and growth rate of 1.29 g/liter/day (by dry wt) was obtained. Plasmin inhibitory activities in the extracts of the results intact plant and in cultured cells of S. japonica were compared and the results indicated that cell suspension culture was superior to extraction the natural plant for inhibitor production.