Journal Article

Selective grazing of methanotrophs by protozoa in a rice field soil

Murase, Jun, Frenzel, Peter

2008

Overview

Biological methane oxidation is a key process in the methane cycle of wetland ecosystems. The methanotrophic biomass may be grazed by protozoa, thus linking the methane cycle to the soil microbial food web. In the present study, the edibility of different methanotrophs for soil protozoa was compared. The number of methanotroph-feeding protozoa in a rice field soil was estimated by determining the most-probable number (MPN) using methanotrophs as food bacteria; naked amoebae and flagellates were the dominant protozoa. Among ten methanotrophic strains examined as a food source, seven yielded a number of protozoa comparable with the yield with Escherichia coli [10⁴ MPN (g soil dry weight)⁻¹], and three out of four Methylocystis spp. yielded significantly fewer numbers [10²-10³ MPN (g soil dry weight)⁻¹]. The lower edibility of the Methylocystis spp. was not explained either by their growth phase or by harmful effects on protozoa. Incubation of the soil under methane resulted in a higher number of protozoa actively grazing on methanotrophs, especially on the less-edible group. Protozoa isolated from the soil demonstrated a grazing preference on the different methanotrophs consistent with the results of MPN counts. The results indicate that selective grazing by protozoa may be a biological factor affecting the methanotrophic community in a wetland soil.

• Publisher: Oxford, UK : Blackwell Publishing Ltd,Blackwell Publishing Ltd,Blackwell,Oxford University Press
• Subject: agricultural soils / Amoeba / Animal, plant and microbial ecology / Animals / Aquatic ecosystems / bacteria / Biological and medical sciences / biomass / Colony Count, Microbial / Culture Media / drug effects / E coli / Ecology / ecosystems / Escherichia coli / Eukaryota / Eukaryota - drug effects / Eukaryota - growth & development / Eukaryota - isolation & purification / feeding preferences / flagellate / Flagellates / Food / Food Chain / Food chains / Food sources / Food webs / Fundamental and applied biological sciences. Psychology / Grazing / grazing preference / growth & development / isolation & purification / Methane / Methane - pharmacology / methane‐oxidizing bacteria / Methanotrophic bacteria / methanotrophs / Methylocystaceae / Methylocystaceae - growth & development / Methylocystis / Microbial ecology / Microbiology / Microorganisms / MPN / naked amoeba / Oryza / Oryza - microbiology / Oryza sativa / Oxidation / Oxidation-Reduction / parasitology / pharmacology / protist / Protozoa / Rice / Soil / Soil - parasitology / soil fauna / Soil Microbiology / Soils / Species Specificity / Weight / wetland soils / Wetlands