GEOCHEMICAL CONSTRAINTS ON COPPER ACQUISITION BY METHANOTROPHIC BACTERIA

Biogeochemistry

Aerobic methanotrophic bacteria oxidize the potent greenhouse gas methane (CH4) most efficiently via the copper (Cu)-bearing enzyme particulate methane-monooxygenase (pMMO). Aerobic CH4 oxidation therefore critically depends on the ability of methanotrophs to acquire Cu. “Cu availability” can be biologically limited in the environment and some methanotrophs have developed a high-affinity Cu acquisition strategy. This strategy involves exudation of biogenic ligands, termed chalcophores, with a high affinity for Cu. This project aims to elucidate kinetic geochemical mechanisms of Cu-acquisition by methanobactin (mb) (pictured below), a well-characterized chalcophore exuded by the aerobic methanotroph Methylosinus trichosporium OB3b.

Cu has a high affinity for sulfides and forms Cu-sulfide phases with low solubility’s which can, upon formation, decrease the biologically available fraction of Cu. Cu-sulfide phases are dominant under reducing or suboxic conditions. We hypothesize that high affinity Cu ligands, such as mb, will have significant effects on the dissolution rates of Cu from such phases. To investigate our hypotheses, we conduct controlled dissolution and absorption experiments from which we can quantify rates and elucidate mechanisms.

We hope to compliment the experimental data here with that of our collaborators who will be working in the field to determine if low Cu concentrations limit the rate of aerobic CH4-oxidation and if this limitation is overcome by mb production and Cu acquisition in the environment.

Collaborating partner:

University of Basel
Biogeochemistry
Department of Environmental Sciences
Prof. Dr. Moritz Lehmann

Dr. Lea Steinle

biogeochem.duw.unibas.ch

Funded by FWF