Co-Culture of a Methanogenic Archaeon and a Methanotrophic Bacterium on Sterilized Soil in Large Test Tubes: Design for Soil-Mediated Co-Culture

Abstract

In a design utilizing a sterilized soil-mediated co-culture of methanogenic archaeon and methanotrophic bacterium, the activities of both the methanogen and methanotroph were examined. It was confirmed that CH₄ was produced by the methanogen after methanotrophic inoculation and suggested that this CH₄ was oxidized by the methanotroph as the concentration of O₂ increased, although emission of CH₄ itself was indirect proof of CH₄-oxidizing activity. On the other hand, in the control treatment, methanogenic inoculation without methanotrophic inoculation at different levels of O₂, CH₄ was not emitted (there was no activity to produce CH₄). These results suggest a symbiotic relation in this co-culture system, because the methanogen provided CH₄ to the methanotroph, while inoculation of the methanotroph was necessary for subsequent production of CH₄ by the methanogen. The development of co-culture systems is essential for understanding the close relationship and interaction between methanogens and the methanotrophs in natural and agricultural environments.