Effect of Bacterial Cell Shape on Transport of Bacteria in Porous Media

Parameters used to describe the transport of colloids (including bacteria) through porous media either implicitly or explicitly account for colloidal particle size but assume that the particles are spheres of uniform size. Bacteria found in soils and in aquifers exhibit a variety of shapes as well as sizes. We sought to determine if there exists a systematic effect of cell shape on the transport of bacteria in columns packed with clean quartz sand. A pulse of resting cells (14 strains of bacteria isolated from aquifers) suspended in an artificial groundwater was passed through a short column. Properties of the bacteria in the influent pulse were compared with those in the eluent from the columns. Cell shape, as quantified by the ratio of cell width to cell length, affects the transport of bacterial cells through porous media. In addition, the distributions of size and shape of cells in the effluent differed from those in the influent suspension with cells in the effluent being smaller and rounder. Short rods with low water contact angles (a measure of cell-surface hydrophobicity) showed the greatest decrease in cell length during passage through short columns.