Group-specific quantification of methanotrophs in landfill gas-purged laboratory biofilters by tyramide signal amplification-fluorescence in situ hybridization

The aim of this study was to quantitatively analyse methanotrophs in two laboratory landfill biofilters at different biofilter depths and at temperatures which mimicked the boreal climatic conditions. Both biofilters were dominated by type I methanotrophs. The biofilter depth profiles showed that type I methanotrophs occurred in the upper layer, where relatively high O₂ and low CH₄ concentrations were present, whereas type II methanotrophs were mostly distributed in the zone with high CH₄ and low O₂ concentrations. The number of type I methanotrophic cells declined when the temperature was raised from 15 °C to 23 °C, but increased when lowered to 5 °C. A slight decrease in type II methanotrophs was also observed when the temperature was raised from 15 °C to 23 °C, whereas cell numbers remained constant when lowered to 5 °C. The results indicated that low temperature conditions favored both type I and type II methanotrophs in the biofilters.