Extraction of methane-oxidizing bacteria from soil particles

• Published in: FEMS microbiology ecology 1996-09, Vol.21 (1), p.59-68
• Main Authors: Prieme, A, Bonilla Sitaula, J.I, Klemedtsson, A.K, Bakken, L.R
• Format: Article
• Language: English
• Subjects: adhesion; Agronomy. Soil science and plant productions; Bacteria; Bacterial adhesion; Biochemistry and biology; Biological and medical sciences; Chemical, physicochemical, biochemical and biological properties; Cultivation; Culture media; density gradient centrifugation; Ecological monitoring; Ecology; extraction; Extraction of soil bacteria; Flotation; Fundamental and applied biological sciences. Psychology; Growth rate; mathematical models; Methane; Methane oxidation; Microbiology; Nycodenz; Oxidation; particles; Percoll; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Separation; soil; Soil bacteria; Soil ecology; Soil microorganisms; Soil science; Soils
• ISSN: 0168-6496; 1574-6941
• DOI: 10.1111/j.1574-6941.1996.tb00333.x

We present a method for extraction of active methane (CH4)-oxidizing bacteria from soil samples. The method is based on physical dispersion of bacteria from the soil particles followed by separation of bacteria and soil particles by flotation in the density media Nycodenz or Percoll. Separation on Nycodenz produced very pure bacterial suspensions while separation on Percoll produced rather impure suspensions. However, more than 60% of the methane-oxidizing activity was irreversibly inhibited in the procedure using Nycodenz compared to less than 10% irreversible inhibition when Percoll was employed. The bacterial suspensions extracted from soil can be used to study the physiology and ecology of soil bacteria that oxidize methane at atmospheric concentrations. Our data indicated that these bacteria are extremely difficult to dislodge from particles compared to the majority of bacteria in soil. Tentatively, we interpret the strong attachment to long residence time (i.e. slow turnover) of the methane-oxidizing bacteria. A slow turnover/growth rate would explain why soil disturbances, like cultivation, have a long lasting effect on the oxidation of atmospheric methane in soil.