Enumeration of microorganisms from deep-sea hydrothermal chimney samples

Enumerating microorganisms from particle-laden environmental samples can often prove difficult. Procedures involving the separation of the cells from the particles are required, as well as an evaluation of the extraction efficiency. Here we present for the first time a method enabling direct counts to be performed on environmental samples of deep-sea hydrothermal vent sulfide chimney samples. This method involves a separation of cells from the metallic sulfide particles by detergent and ultrasound treatments, followed by an estimation of the extraction efficiency by the Leslie regression method. Successful counts were obtained from the outer portions of two active chimneys from the Mid-Atlantic Ridge, and from the East Pacific Rise. The outer crust of these chimneys contained up to ca. 1010 cells g−1 of chimney (dry weight).