Isolation and Characterization of Bacteria from Free Ranging Sheep and Goats Tolerant to Toxic Compound(s) in Acacia Angustissima leaves

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Addis Ababa Universty


The study was conducted at the ILRI-Debre Zeit Research Station to screen the various extracts of Acacia anglls/issillla for evidence of toxicity using mixed and pure cultures of bacteria, and to isolate bacteria capable of tolerating or detoxifYing the toxic principle. Gas production was llsed as an index of fermentation to screen the amino acid, non-basic, chloroform and ethanol extracts from A. anglls/issillla leaves for toxicity to mixed and pure rumen microbes. RlIlllinococclls a/blls 7, R. jlavefaciens FD-l, R. a/blls 1Il0Z a, Prevo/ella rlllllinico/a D31D, Se/enolllonas rlllllinantiulII D, Blltyrivibrio jlbriso/vens, and StreptococCllS bovis JB 1 were used as pure cultures. Alfalfa and elephant grass were used as substrates. The extracts were used at 0, 5, 10,20,30 and 50 % ofthe substrates. The samples were incubated at 39°C for 120 h. Gas production, ammonia released and volatile fatty acid were estimated. The result showed that ethanol, chloroform and non-basic extracts but not the amino acid were toxic to the mixed rumen microbes. All the three extracts inhibited the growth of all pure cultures except Se/enolllonas rlIl11inantlllll. Extracts containing tannin were more inhibitOlY to rumen bacteria suggesting that tannin was one of the problem compound in A. anglls/issillla. Experiments were subsequently set to isolate tannin tolerant or degrading bacteria. Tannin was extracted from A. angllstissillla and Calliandra ca/othyrslls leaves. Four straight rods and three spherical bacteria were isolated using roll tubes emiclled with tannic acid inoculated with rumen fluid from sheep and goats. The isolates were characterized by morphology, products of fermentation and restriction fragment length polymorphism (RFLP). Morphological, fermentative and RFLP characterization indicate that the cocci isolates were Streptococclls while the rods were closely related to recently isolated tannin tolerant bacteria (ES 14.2) which had been shown to cluster with Klebsiella