Energy-dependent, high-affinity transport of nickel by thermophilic acetogenic bacteria

Author

• Hsiuchin Yang

Date of Award

5-1989

Document Type

Thesis

Degree Name

M.S. in Biological Science

Department

Biology

First Advisor

Dr. Harold Drake

Second Advisor

Dr. Nick Aumen

Third Advisor

Dr. Lyman Magee

Relational Format

Dissertation/Thesis

Abstract

Nickel plays an essential role in acetogenesis at the level of acetyl-CoA synthetase, and the mechanism of nickel transport is therefore central to the metabolic capacities of acetogens. The mechanism of nickel transport by the thermophilic acetogenic bacteria Clostridium thermoaceticum ATCC 39073 and Acetogenium kivui ATCC 33488 was investigated using ⁶³NiCl₂ and an anaerobic microfiltration transport assay. Nickel transport by C. thermoaceticum was optimal at pH 7-7.5 and 65°C; nickel transport by A. kivui was optimal at pH 6.4 and 65°C. Cells during the early stages of growth displayed the highest propensity for nickel transport. Nickel transport was linear during the transport assay period and displayed saturation kinetics. The apparent Km and Vmax for nickel transport by carbon monoxide cultivated C. thermoaceticum approximated 3.2 μM Ni and 400 pmol Ni transported per min per mg of cells (dry weight), respectively. The apparent Km and Vmax for nickel transport by hydrogen cultivated A. kivui approximated 2.3 μM Ni and 670 pmol Ni transported per min per mg of cells (dry weight), respectively. Magnesium, calcium, cobalt, iron, manganese, and zinc did not significantly inhibit the transport of nickel, and transported nickel was not readily exchangeable with exogenous nickel. Nickel transport of A. kivui was stimulated by glucose or H₂ and was decreased by various metabolic inhibitors; however, nickel uptake by glucose- and H₂-dependent cells displayed differential sensitivity to ATPase inhibitors. Stored cellular energy appeared to provide a short-term energy source to power nickel transport. Preincubation experiments with C. thermoaceticum demonstrated external energy source stimulation of nickel translocation. Based on polyacrylamide gel electrophoretic analyses, exogenous ⁶³Ni was incorporated into carbon monoxide dehydrogenase when A. kivui was cultivated in the presence of ⁶³NiCl₂; a putative nickel-containing hydrogenase was also detected. These studies demonstrate that acetogenic bacteria utilize energy-dependent, high-affinity nickel transport systems for the translocation of this element.

Recommended Citation

Yang, Hsiuchin, "Energy-dependent, high-affinity transport of nickel by thermophilic acetogenic bacteria" (1989). Electronic Theses and Dissertations. 8886.
https://egrove.olemiss.edu/etd/8886

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