Trimethylamine-N-oxide reduction by alteromonas spp.

Easter, M.C.

Abstract

Trimethylamine-N-oxide (TMAO) is a nitrogenous compound widely distributed in marine fish and invertebrates. It has long been known that TMAO is reduced by bacteria during the post mortem spoilage of iced marine fish, but the mechanism involved and the physiological role have remained unknown. Studies with Escherichia coli suggested that TMAO acted as a terminal electron acceptor supporting anaerobic growth, but few studies have been performed with fish spoilage organisms. The work presented here describes some of the properties of TMAO reduction in typical fish spoilage bacteria, Alteromonas spp., and comparisons made with that of E.coli. TMAO reduction was shown to be a property of several Gram negative bacteria and it supported anaerobic growth. It was not confined to marine bacteria and only certain marine species could reduce TMAO. In Alteromonas sp., NGMB 400, the enzyme TMAO reductase was induced by TMAO, and repressed by oxygen and fumarate but not nitrate. Membrane-bound cytochrome C552 and TMAO reductase were simultaneously induced. TMAO reductase was located predominantly in the periplasm, but difficulties were encountered with cell fractionation and the results are discussed with reference to the cell wall structure. The enzyme was partially purified using affinity chromatography and some biophysical characteristics determined. The kinetic properties of the enzyme were determined using resting cell suspensions and partially purified preparations. Similarities and differences were observed in the TMAO reductases of Alteromonas sp. and E.coli. TMAO reductase has the properties of an anaerobic respiratory enzyme, and appears to be similar to nitrite reductase. A possible mechanism for energy conservation coupled to TMAO reduction is proposed in terms of the chemiosmotic hypothesis. TMAO reduction has significance in fish spoilage; it probably confers a competitive advantage to certain spoilage organisms, and thus the accumulation of trimethylamine in spoiling fish is not a fortuitous association as has been suggested.

Citation

EASTER, M.C. 1982. Trimethylamine-N-oxide reduction by alteromonas spp. Robert Gordon's Institute of Technology, PhD thesis. Hosted on OpenAIR [online]. Available from: https://doi.org/10.48526/rgu-wt-1993256

• Thesis Type: Thesis
• Deposit Date: Oct 2, 2024
• Publicly Available Date: Oct 2, 2024
• DOI: https://doi.org/10.48526/rgu-wt-1993256
• Public URL: https://rgu-repository.worktribe.com/output/1993256
• Award Date: Feb 28, 1982