Separation of bacteria by sedimentation field-flow fractionation

Growth of the soil bacterium Stenotrophomonas maltophilia in the presence of selenite produced a mixture of two types of cells: those that contained numerous electron-dense bodies of elemental selenium and those that did not. Light diffraction and electrical impedance measurements indicated that the cells that contained visible bodies of elemental selenium were approximately 30% larger than the cells that exhibited no visible accumulation of selenium. Sedimentation field-flow fractionation was applied to a stationary-phase culture of bacteria growth in the presence of 2.0 mM selenite. Complete separation of selenium-free cells from those that contained elemental selenium was achieved at a field strength of 331 cm/s(2). (C) 1997 John Wiley & Sons, Inc.