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|Title: ||An investigation into some antibiotics produced by Pseudomonas antimicrobica|
|Authors: ||Attafuah, Ernest|
|Issue Date: ||1991|
|Publisher: ||© Ernest Attafuah|
|Abstract: ||Two strains (NCm 9897 and 9898; strains A and B respectively) of a Pseudomonas·
species have been shown to display antifungal and antibacterial activity on solid
media. Biochemical tests indicate that the organisms may be two distinct strains of
a new species. Cell morphology was studied using scanning electron microscopy.
Chemically defined media, established for the organisms, indicate non-fastidous
Four liquid media, able to elicit antibiotic production from Strain A have been
developed: a chemically defined medium (antibacterial), a chemically defined
medium and a complex medium (antifungal) and a chemically defined medium
(antibacterial and antifungal). Nitrogen and magnesium limitation significantly increased yields. Magnesium content
in a medium (without a magnesium salt component) and in whole cell samples grown
in the said medium were assessed using atomic absorption spectroscopy and
elemental analysis respectively.
Optimization experiments for antibacterial and antifungal activity, assessed by a disc
diffusion assay, increased yields, in 250 ml conical flasks by a factor of X9 and 109%
respectively. A 6 litre laboratory-scale fermentor was used for larger batch
Procedures for extraction of the active compounds from the biological matrices were .
developed leading to the isolation of one antibacterial compound, ABl (yellow
crystalline) and three antifungal compounds, AFl, AF2 and AF3 (pale yellow and
amorphous). Structure determination of ABl, involving mass spectrometry, IR/UV spectroscopy,
lH-NMR and x-ray diffraction, indicated it to be 1.6 dimethyl pyrimido[5,4-e ]-1,2,4-
triazine-5,7(IH,6H)-dione (Xanthothricin; Toxoflavin), a toxic metabolite previously detected in foods contaminated with Ps. cocovenenans. Selective media, developed '
for Strain A and Strain B, did not support growth of Ps. cocovenenans. Preliminary
structural analysis suggests that AFl may possess a mono-substituted ring system with
CHz chain and a terminal hydroxyl group; that AF2 may belong to the polyene group
of antifungal antibiotics and that AF3 may be an aliphatic ketone with hydroxyl
Agar diffusion, minimum inhibitory concentration, assays for the compounds, indicate
activity to be in the ~gml range for sensitive microorganisms. Antibiotic challenge
against test microorganisms suggest bacteriostatic activity for ABl, fungistatic activity
for AFl and AF3 and fungicidal activity for AF2.|
|Description: ||A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Chemistry)|
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