Allelopathic Effects of Water Hyacinth [Eichhornia crassipes]

Eichhornia crassipes (Mart) Solms is an invasive weed known to out-compete native plants and negatively affect microbes including phytoplankton. The spread and population density of E. crassipes will be favored by global warming. The aim here was to identify compounds that underlie the effects on microbes. The entire plant of E. crassipes was collected from El Zomor canal, River Nile (Egypt), washed clean, then air dried. Plant tissue was extracted three times with methanol and fractionated by thin layer chromatography (TLC). The crude methanolic extract and five fractions from TLC (A–E) were tested for antimicrobial (bacteria and fungal) and anti-algal activities (green microalgae and cyanobacteria) using paper disc diffusion bioassay. The crude extract as well as all five TLC fractions exhibited antibacterial activities against both the Gram positive bacteria; Bacillus subtilis and Streptococcus faecalis; and the Gram negative bacteria; Escherichia coli and Staphylococcus aureus. Growth of Aspergillus flavus and Aspergillus niger were not inhibited by either E. crassipes crude extract nor its five fractions. In contrast, Candida albicans (yeast) was inhibited by all. Some antialgal activity of the crude extract and its fractions was manifest against the green microalgae; Chlorella vulgaris and Dictyochloropsis splendida as well as the cyanobacteria; Spirulina platensis and Nostoc piscinale. High antialgal activity was only recorded against Chlorella vulgaris. Identifications of the active antimicrobial and antialgal compounds of the crude extract as well as the five TLC fractions were carried out using gas chromatography combined with mass spectroscopy. The analyses showed the presence of an alkaloid (fraction A) and four phthalate derivatives (Fractions B–E) that exhibited the antimicrobial and antialgal activities

Effect of antifungal agents on the physiological activities of towo plant pathogenic fungi: Rhizoctonia solani & Fusarium oxysporum

Each of the antifungal compounds extracted from each of the antagonistic microorganisms was found to has an inhibitory effect on Rhizoctonia solani and Fusarium oxysporum. Four antifungal compounds were found to be the most inhibitory than the other compounds. The first one from Eupenicillium senticosum, the second from Streptomyces aurantiacus, the third from Curtobacterium pusillum and the last one from Saccharomyces unispora respectively. The first three compounds were active against R. solani, while the last one was active against F. oxysporum. All the four compounds reduce or inhibit the growth of Rhizoctonia solani and Fusarium oxysporum. They also reduced the carbohydrate concentrations, as well as reducing the nitrogen content (total nitrogen, soluble nitrogen and protein nitrogen). Regarding their effects on the enzyme activity, the active compounds increased the activity of fumarase, malic dehydrogenase and succinic dehydrogenase, the activity of catalase enzyme of both R. solani and F. oxysporum was sharply decreased by such compounds as compared to control.Egyptian Journal of Biotechnology Vol. 25 (1) 2007: pp.159-16

Induction of resistance and biocontrol of rhizoctonia in cotton against damping-off disease by rhizosphere microorganisms.

Addition of fishmeal to the soil infested with the pathogen led to a remarkable reduction in the percentage of disease compared to the soil non-amended with fishmeal. 28 fungal isolates, 22 yeast isolates, 43 isolates of actinomycetes and 8 isolates of bacteria were isolated from the rhizosphere associated soil of cotton plant. Three fungal isolates, 3 yeast isolates, 4 isolates of actinomycetes and 4 isolates of bacteria were characterized by their potent and remarkable antagonistic activities, and were identified as: Eupenicillium senticosum, Penicillium herquer, Trichoderma viride, Hansenula arabitolgenes, Candida incommunis and Candida steatolytica, Streptomyces erumpens, S. purpureus, S. aurantiacus, S. microflavus , Arthrobacter ramosus, Aureobacterium terregens, Curtobacterium pusillum and Pseudomonas putida respectively. The use of a mixture of fungal, yeast, actinomycete and bacterial species led to an increase in inhibition of the pathogen, an increase in induction of resistance of cotton plant and an increase in growth measurements of cotton plant than each of them alone. Candida incommunis, S. purpueus and A. ramosus have the ability of solubilizing phosphate and have the ability for production of indolacetic acid (IAA) and siderophores. New Egyptian Journal of Microbiology Vol. 17 (2) 2007: pp. 148-16

Isolation, identification and chemical characterization of antifungal compounds isolated from rhizosphere microorganisms antagonizing the fungal pathogen: Rhizoctonia solani.

Four species of actinomycetes, 4 species of bacteria, 3 species of yeasts and 3 species of fungi were selected for their highest inhibitory and antagonistic activity and it was found that Streptomyces aurantiacus and Hansenula arabitolgenes were the most inhibitory followed by S. purpureus. It was also found that actinomycetes represent the most inhibitory group of the tested groups of microorganisms. One of the tested species produces 6 active components, 8 species, each produce 5 active components and the remaining other, each produce 4 active components. One of these active components was separated from the culture filtrates of 7 species. Two active components were separated from the culture filtrates of 6 species. One active component was separated from the culture filtrate of 5 species. The active components were purified and chemically analyzed to determine their chemical names, chemical formulae and molecular weight. New Egyptian Journal of Microbiology Vol. 17 (2) 2007: pp. 129-14