Co-cultivation of the strictly anaerobic methanogen Methanosarcina barkeri with aerobic methanotrophs in an oxygen-limited membrane bioreactor

Abstract

Wetlands contribute to 30% of global methane emissions due to an imbalance between microbial methane production and consumption. Methanogenesis and methanotrophy have mainly been studied separately, and little is known about their potential interactions in aquatic environments. To mimic the interaction between methane producers and oxidizers in the environment, we co-cultivated the methanogenic archaeon Methanosarcina barkeri with aerobic Methylocystaceae methanotrophs in an oxygen-limited bioreactor using acetate as methanogenic substrate. Methane, acetate, dissolved oxygen, available nitrogen, pH, temperature, and cell density were monitored to follow system stability and activity. Stable reactor operation was achieved for two consecutive periods of 2 months. Fluorescence in situ hybridization micrographs indicated close association between both groups of microorganisms. This association suggests that the methanotrophs profit from direct access to the methane that is produced from acetate, while methanogens are protected by the concomitant oxygen consumption of the methanotrophs. This proof of principle study can be used to set up systems to study their responses to environmental changes.Electronic supplementary materialThe online version of this article (10.1007/s00253-018-9038-x) contains supplementary material, which is available to authorized users.

Effect of concentration and hydraulic reaction time on the removal of pharmaceutical compounds in a membrane bioreactor inoculated with activated sludge

“…The plate was incubated for one hour in the dark at room temperature and measured at 405 nm in the plate reader. Finally, acetate was measured by GC‐MS using the protocol described in a previous study (in ’t Zandt et al ., 2018). Briefly, 200 µl of 100 mM pentafluorobenzyl bromide solution in acetone, 40 µl of 0.5 M phosphate buffer pH = 6.8 and 40 µl of sample/standard were mixed in an Eppendorf tube and incubated for one hour at 60 °C.…”

Do initial concentration and activated sludge seasonality affect pharmaceutical biotransformation rate constants?

“…Ammonium, nitrite, and nitrate assays were performed with technical duplicates in 96-well microtiter plates. Ammonium was measured at 420 nm on a 96-well fluorescence spectrophotometer after reaction with OPA reagent (0.54% (w/v) ortho-phthaldialdehyde, 0.05% (v/v) β-mercaptanol, and 10% (v/v) ethanol in 400 mM potassium phosphate buffer (pH 7.3)) as previously described (In’t Zandt et al 2018 ). The reaction volumes were adjusted to the 96-well plate: 10 µL of sample and 200 µL of OPA reagent.…”

Challenges and Approaches of Culturing the Unculturable Archaea

“…Similarly, biotic and abiotic factors for archaeal growth in a laboratory setting differ greatly from the natural environments. These factors limit the cultivable archaea to only a few isolates [61,62]. Several strategies have been reported for archaea's successful isolation and growth by coinciding the growth conditions with environmental conditions regarding temperature, pH, nutrients, pressure, and gasses.…”

“…In instances like the growth of methanotrophic and methanogens, each provides an environment for the growth of the other. The methanotrophic archaea utilize oxygen and provide an anaerobic condition for methanogen, which produces CH 4 utilized by the methanotrophs for the carbon source [61]. Many successful examples of archaea isolated through the co-culture approach include recent clinical pathogenic archaea from dental samples.…”