Chapter 11, Problem 8CHI

The archaeon Metallosphaera sedula is of great interest to microbiologists in the field of biomining because it might be used to recover base and precious metals. This aerobic thermoacidophile can use organic carbon, ferrous iron (Fe²⁺), and reduced inorganic sulfur compounds including elemental sulfur (S⁰) and tetrathionate (S₄O₆^2–) as a source of electrons. Thus M. sedula can grow chemoorganotrophically and chemolithotrophically. Genome sequencing reveals that M. sedula has five major terminal oxidase complexes.

Refer to table 10.2 and figure 11.10 to propose the flow of electrons through the electron transport chain when using each of these compounds as the electron source. Which will conserve the most energy and which the least? Why do you think this microbe requires five different terminal oxidases if it always uses O₂ as the terminal electron acceptor?

Read the original paper: Auernik, K. S., and Kelly, R. M. 2008. Identification of components of electron transport chains in the extremely thermoacidophilic crenarchaeon Metallosphaera sedula through iron and sulfur oxidation transcriptomes. App. Environ. Microbiol. 74:7723.