Anaerobic Methane Incubation System

The Anaerobic Methane Incubation System, or AMIS, is a continuous flow bioreactor designed to mimic in situ conditions (e.g., temperature, pressure, advective fluid flow, etc.) at seeps and other novel deep sea environments, such as hydrothermal vents, with minimal disturbance of the microbial communities. A significant benefit of the AMIS is that it enables environmentally relevant experiments over long periods of time without concern for substrate depletion or endproduct inhibition that is observed in static incubations and can easily restrict growth. This “artificial seep” system was first used to successfully study the growth and metabolism of anaerobic methanotrophic archaea (ANME) thought to be restricted to deep ocean environments with high methane concentrations (Girguis et al., 2003; Girguis et al., 2005). ANME phylotypes mediate the anaerobic oxidation of methane (AOM), which represents a globally significant sink that dramatically regulates the amount of methane released to the atmosphere. Indeed, AOM rates measured in AMIS are comparable to published in vitro and in situ measurements of AOM (Alperin et al., 1988; Thomsen et al., 2001; Orcutt et al., 2005), and provide some of the first, and arguably most robust, estimates of methanotrophic archaeal growth at different conditions.

Recently, a modified version of the AMIS was utilized for incubation of hydrothermally-influenced sediments at high temperature and under continual supply of reactants allowing for quantification of significant AOM rates over time and ANME phylotypes over the thermal gradient (Wankel and Adams et al).

Figure 1. Two of four low temperature AMIS reactors are shown in operation in a 7° Celsius coldroom. Sediments are irrigated from the bottom with methane and sulfide-rich porewater-like fluids, through gastight fittings and tubing. Sediments are also irrigated on the top with aerobic filtered seawater.

Figure 2. A modified AMIS capable of incubating sediments at temperatures up to 90° Celsius. Here we subjected sediments from the Middle Valley hydrothermal vent system to thermal gradients we observe in situ (~25 to 90°C) to examine the influence of temperature on anaerobic methane oxidation and sulfate reduction.