FIG. 6.

Survival of wild-type E. faecalis strain JH2-2 (squares) and the derivative mutants S26 (cross), AS39 (triangles), and SAS (circles) under different lethal stress conditions. Cells were grown in GM17 to an optical density at 600 nm of 0.5 and submitted to heat challenge at 62°C (A), ethanol stress (22% ethanol) (B), or acid treatment (pH 3.2) (C). The values shown are means ± the standard deviations of three independent experiments. Percent viability represents the ratio of the survival number after exposure to challenge conditions to the survival number prior to the challenge. Panel D shows one representative experiment of the long-term survival of the four strains in seawater (oligotrophic medium).