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Three organic extracts (chloroform, ethyl acetate and n-butanol) of ten cyanobacterial species (Anabaena solitaria, Anabaena variabilis, Anabaena cylindrical, Anabaena spiroides, Anabaena circinalis, Oscillatoria ornate, Oscillatoria salins, Oscillatoria tenuis, Oscillatoria rubescens andOscillatoria prolifica) were investigated for their antibacterial activities against 4 fish pathogenic bacterial species belonging to genus Aeromonas, namely, Aer. salmonicida, Aer. hydrophila, Aer. formicans and Aer. liquefaciens using oxytetracycline as reference antibiotic. Of all cyanobacterial samples, only ethyl acetate extracts of A. variabilisand A. circinaliswere proved to be the most effective against all tested Aeromonas species. Bioautographic investigation for 13 organic solvent systems indicate that the spot with Rf = 0.79 for A. variabilis and that of Rf = 0.84 for A. circinalis were the most effective. The median lethal doses (LD50) for the purified antibacterial compounds against mice were 246.67 and 231.67 mg/kg for that extracted from A. variabilis and A. circinalis, respectively.
Key words:Cyanobacteria, Anabaena, antibacterial activity, fish pathogenic Aeromonas species.
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African Journal of Microbiology Research Vol. 6(38), pp. 6720-6725, 4 October, 2012
Available online at http://www.academicjournals.org/AJMR
DOI: 10.5897/AJMR12.1129
ISSN 1996-0808 ©2012 Academic Journals
Full Length Research Paper
Cyanobacterial extra-metabolites against some pathogenic bacteria
Ibraheem B. M. Ibraheem1*, Monerah R. Al-Othman1 and Neveen Abdelraouf1,2
1Botany and Microbiology Department, Faculty of Science, King Saud University, Riyadh, Kingdom of Saudi Arabia.
2Botany Department, Faculty of Science, Beni-Suef University, Beni-Suef, Egypt.
Accepted 24 September, 2012
Ten cyanobacterial species (Nostoc calcicola, Nostoc commune, Nostoc entophytum, Nostoc minutum, Nostoc palndosum, Nostoc passerianum, Nostoc punctiforme, Anabaena ambigua, Anabaena amomala, and Anabaena doliolum) were isolated from the mangrove region of Ras Mohammed (Sinai, Egypt), and were tested for their allelopathic activities including inhibitory and/or promoting effects against two Gram positive bacteria (Bacillus subtilis and Staphylococcus aureus) and two Gram negative bacteria (Escherichia coli and Pseudomonas aeruginosa). Data suggested two types of allelopathic effects: one type which always appeared in cyanobacterial medium as in the case with N. minutum (medium that inhibits the growth of all tested bacterial species). The other type is induced only when cyanobacteria are in contact with bacteria; this is the case when the growth of both B. subtilis and S. aureus were inhibited in co-culture with N. commune. On the other hand, promotion effects of bacterial growth were observed when grown in cyanobacterial metabolites in most of studied cyanobacterial species. The biological assays for aqueous and methanolic extracts of the two Nostoc species revealed that both extracts for each species were not toxic at concentrations of 0.52 and 0.59 g L-1 water extract for N. commune and N. minutum, respectively and 0.31 and 0.425 g L-1 for methanolic extract for N. commune and N. minutum, respectively. No mortality was observed in tested mice within 72 h.
Key words: Allelopathic activity, cyanobacteria, pathogenic bacteria.
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Antibiotic activity of two.pdf