Separation of bacteria from a methanogenic wastewater population by utilizing a self-generating Percoll gradient

Bacteria from a methanogenic wastewater population could be separated with a self-generating density gradient of Percoll. The separation was performed by centrifugation for 30 min at 30000 g in a simple angle-head rotor. Three types of bacteria were concentrated to apparent homogeneity in different bands; these were attributed to the methanogens Methanosarcina and Methanothrix , and to the dissimilatory sulphate-reducing bacterium Desulfovibrio. The described technique will contribute to a rapid diagnosis of the bacterial types that are active in waste-water treatment.