Publication Date


Document Type


First Advisor

Meganathan, Rangaswamy

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Biological Sciences


Escherichia coli; Bacterial growth


The use of tetrahydrothiophene-l-oxide (THTO) as a terminal electron acceptor during anaerobic growth of Escherichia coli was investigated. The organism grew anaerobically in the presence of THTO using the non-fermentable carbon source, glycerol. THTO was reduced enzymatically to tetrahydrothiophene (THT) which was detected by a gas chromatographic method developed for this study. This reduction was demonstrated in cell-free extracts using various physiological electron donors, of which NADH and formate worked most efficiently. Artificial donors benzyl viologen, methyl viologen and dithionite could also function. Centrifugation of the extracts indicated that the reductase is membrane-bound. Presence of the reductase was shown to be constitutive, but under anaerobic conditions in glycerol medium the enzyme concentration increased more than twofold. Lower enzyme activities were observed with glucose-grown cells. Mutants lacking a functional molybdenum cofactor, chlA, chlB, chlD and chlE, were unable to grow using THTO as electron acceptor. However, growth and ability to reduce THTO could be restored in the chlD mutant in the presence of a high level of molybdate. This result suggested that molybdenum cofactor is required for THTO reduction. Likewise, mutants blocked in the biosynthesis of menaquinone, menB, menC and menD, could not grow with THTO as the terminal oxidant. Growth and THTO reduction were restored in the men mutants when intermediates of the menaquinone biosynthetic pathway were supplied. Depending on the metabolic block, either o̲-succinylbenzoic acid (OSB) or 1,4-dihydroxynaphthoic acid (DHNA) was able to restore growth. This indicated that menaquinone is a necessary element of the respiratory chain leading to THTO reduction.


Bibliography: pages [40]-43.


v, 43 pages




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