Bacterial decomposition of streptomycin

Ravani, Shakuntala Hansraj (1967) Bacterial decomposition of streptomycin. MSc(R) thesis, University of Glasgow.

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The aim of the project was to elucidate the kinetics of streptomycin decomposition by soil bacteria. Primary investigations involved experiments such as adding 1000 p.s of streptomycin/gm of sterile and non-sterile soil and studying its stability and both, the cause and the course of its disappearance. It was found that most of the added streptomycin was strongly adsorbed on soil colloids. The evidence that the disappearance of added streptomycin from normal soil as compared to its constant recovery from sterile soil, and an increase in the microbial population. simultaneous to decomposition of the antibiotic from the normal soil, suggested that streptomycin was microbiologically decomposed. Soil was repeatedly treated to enrich it with the streptomycin decomposing organism, and the course of decomposition of successive additions of streptomycin was followed. Samples of "Soil extract" (mixed soil population) from the above "active Soil" in which streptomycin had been decomposed were introduced into bentonite containing laboratory synthetic media with streptomycin as the sole source of carbon and nitrogen and the course of degradation of streptomycin was studied; bentonite was added to the medium, to make conditions similar to thosein soil. In these media all except 20 mug of streptomycin/ml of medium was adsorbed on the clay, and the free streptomycin was decomposed in 4-5 days after an induction period in which no decomposition took place. Parallel experiments were performed with synthetic media containing 20 mug/ml of antibiotic and no bentonite; the streptomycin in this case, too, was decomposed in similar manner. Degradation of streptomycin in both these types of media was studied under different environmental conditions. Mixed cultures which decomposed streptomycin were isolated and isolates obtained were studied for their ability to decompose streptomycin in synthetic media containing streptomycin as the sole source of carbon and nitrogen (streptomycin-synthetic-medium). A detail characterization and identification of one of the prominent and active isolates was carried out; the isolate was identified as a member of the family Corynebacteriaceae. belonging to the genus Cellulomonas, Viz. Cellulomonas fimi. Studies similar to those done with mixed cultures were carried out to investigate the kinetics of streptomycin decomposition by this organism. The above experiments showed that the organism decomposed streptomycin (20 mug/ml) incorporated in the streptomycin-synthetic-medium in 21 days with an induction period of 18 days in which no decomposition took place. An important observation was, that though there was no decrease in the streptomycin content during the induction period, there was a hundred-fold increase in the total viable cell numbers of the organism within 24. hours. It is interesting to note that decomposition of streptomycin was always associated with an amine-like odour. Successive additions of antibiotic (20 mug/ml) made in the same medium after the previous dose had disappeared, were decomposed without any induction period. washed cell suspensions taken from the culture after decomposition were able to degrade streptomycin in fresh streptomycin-synthetic-medium in 7 days with an induction period of 4 days. In this case the maximum viable cell numbers were obtained in 7 days, which suggested a competition between the enzymes involved in the synthesis of cell building material and the streptomycin decomposing enzymes. Of considerable importance were the experiments performed to investigate the energy sources for the multiplication of the organism during the induction period, which showed that ANALAR salts such as MgSO4.7H2O and CaCl2 were responsible in part, if not entirely, for growth.

Item Type: Thesis (MSc(R))
Qualification Level: Masters
Additional Information: Adviser: Joseph Meyrath
Keywords: Microbiology, Soil sciences
Date of Award: 1967
Depositing User: Enlighten Team
Unique ID: glathesis:1967-72221
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 24 May 2019 15:12
Last Modified: 24 May 2019 15:12

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