Surface properties of cells of Pseudomonas aeruginosa possessing R-factor-mediated resistance to gentamicin

The surface properties of cells of Pseudomonas aeruginosa which are sensitive to gentamicin are markedly different from those which are resistant to gentamicin. Cells of four out of five strains in which gentamicin-resistance is R-factor-mediated have electrokinetic properties characteristic of gentamicin-sensitive cells. The surface properties of transconjugant strains are indistinguishable from those of the original acceptor strain. Cells of the remaining R-factor donor strain (which transferred very low gentamicin-resistance) exhibited surface properties characteristic of gentamicin-resistant cells. Gentamicin-resistance in cells of this strain is thus the result of at least two different mechanisms. The results are discussed in terms of possible alternative mechanisms of resistance.