Comparative antifungal activities and biochemical effects of monoterpenes on plant pathogenic fungi

The antifungal activity of twelve monoterpenes, camphene, (R)-camphor, (R)-carvone, 1,8-cineole, cuminaldehyde, (S)-fenchone, geraniol, (S)-limonene, (R)-linalool, (1R,2S,5R)-menthol, myrcene and thymol was evaluated against four plant pathogenic fungi Rhizoctonia solani, Fusarium oxysporum, Penecillium digitatum and Asperigallus niger by using mycelial growth inhibitory technique. (S)-limonene and thymol were examined for their inhibitory effects on pectin methyl esterase (PME), cellulase and polyphenol oxidase (PPO) of tested fungi. Thymol was the most potent antifungal compound against the four test fungi with EC₅₀ values of 33.50, 50.35, 20.14 and 23.80 mg/L on R. solani, F. oxysporum, P. digitatum and A. niger, respectively. The antifungal activity of thymol was comparable to a reference fungicide, carbendazim. (S)-limonene and 1,8-cineole exhibited pronounced antifungal activity against the four tested fungi. The most effective antifungal compounds thymol and (S)-limonene showed strong inhibitory effect on the activity of PME and cellulase but revealed no inhibitory effect on PPO. The results showed that PME was more sensitive than cellulase to thymol and (S)-limonene. This is the first report on the inhibitory effects of monoterpenes thymol and (S)-limonene on PME, cellulase and PPO. The results indicated that monoterpenes may cause their antifungal activity by inhibiting PME and cellulase. The strong antifungal activity of thymol, (S)-limonene and 1,8-cineole reported in this study indicated that these compounds have a potential to be used as fungicides.     

Activity measurements of Ni2+ in soils

Nickel activities were measured in 11 alkaline and slightly acidic soils using the chelate method. The measured activities ranged from 10^?6.82 to 10^?8.78 M and were inversely related to the pH of the soils. The measured Ni²⁺ activities in the 11 soils could be predicted using the following expression: (Ni²⁺) = 10^6.95 (H⁺)². The solubility of Ni was plotted on a log (Ni²⁺) vs. pH solubility diagram for various Ni solid phase compounds. It is most likely that NiFe₂O₄ (trevorite) is the solid phase controlling Ni solubility in these soils. Identification of the presence of this mineral needs further investigation.     

A reversibly switching surface

We report the design of surfaces that exhibit dynamic changes in interfacial properties, such as wettability, in response to an electrical potential. The change in wetting behavior was caused by surface-confined, single-layered molecules undergoing conformational transitions between a hydrophilic and a moderately hydrophobic state. Reversible conformational transitions were confirmed at a molecular level with the use of sum-frequency generation spectroscopy and at a macroscopic level with the use of contact angle measurements. This type of surface design enables amplification of molecular-level conformational transitions to macroscopic changes in surface properties without altering the chemical identity of the surface. Such reversibly switching surfaces may open previously unknown opportunities in interfacial engineering.     

The extent of genetic diversity among Vanilla species: Comparative results for RAPD and ISSR

Vanilla is a large genus of about 110 species in the orchid family (Orchidaceae), including the species Vanilla planifolia from which commercial vanilla flavoring is derived. Since most species of vanilla are considered rare and endangered there is an urgent need to conserve them through genetic analysis and propagation/conservation studies on this crop.The present study investigated the genetic diversity among nine leafy- and leaf-less Vanilla species employing 30 decamer RAPD primers and 10 ISSR primers. The species under study were diverse and displayed a range of variability (0–66% and 0–81% for RAPD and ISSR, respectively). A total of 154 RAPD polymorphic markers (83.24%, h = 0.378) and 93 ISSR polymorphic markers (86.11%, h = 0.363) were used to generate a genetic similarity matrix followed by the cluster analysis. Specific groupings were revealed by each cluster analysis with slight variation between two different markers. Among the nine species studied, V. planifolia, Vanilla aphylla and Vanilla tahitensis revealed very low level of variation within their collections, thus indicating a narrow genetic base. The large genetic distance of Vanilla andamanica from other species suggests its different origin. A close genetic affinity was observed between the pairs V. planifolia, V. tahitensis and Vanilla albida, V. aphylla. These are the first comparative results for RAPD and ISSR reporting inter-relationship among nine cultivated, wild and hybrid Vanilla species.     

Studies on amylase inhibitors in some Egyptian legume seeds

Amylase inhibitor activity was determined in four legume seeds which are widely consumed in Egypt. The effect of dehulling, heat treatment, soaking and germination were also assessed. The results showed that faba bean contained the highest activity of amylase inhibitor followed by cowpea, lentils, then chickpea. Dehulling resulted in raising the amylase inhibitor activities in all samples investigated, while heat treatment and cooking lowered it. Soaking for 10 h and germination eliminated completely the inhibitor from all samples.     

Emerging Trends in Genetic Engineering of Microalgae for Commercial Applications

Recently, microalgal biotechnology has received increasing interests in producing valuable, sustainable and environmentally friendly bioproducts. The development of economically viable production processes entails resolving certain limitations of microalgal biotechnology, and fast evolving genetic engineering technologies have emerged as new tools to overcome these limitations. This review provides a synopsis of recent progress, current trends and emerging approaches of genetic engineering of microalgae for commercial applications, including production of pharmaceutical protein, lipid, carotenoids and biohydrogen, etc. Photochemistry improvement in microalgae and CO₂ sequestration by microalgae via genetic engineering were also discussed since these subjects are closely entangled with commercial production of the above mentioned products. Although genetic engineering of microalgae is proved to be very effective in boosting performance of production in laboratory conditions, only limited success was achieved to be applicable to industry so far. With genetic engineering technologies advancing rapidly and intensive investigations going on, more bioproducts are expected to be produced by genetically modified microalgae and even much more to be prospected.