FIG. 6.

Sucrose and glucose suppress the growth defect and leaky phenotype of the Δeps mutant strain. (A) Growth of wild-type, NΔeps, and NΔeps+pEps strains of V. cholerae N16961 in LB broth or LB broth supplemented with sucrose (LBS) at a 5% final concentration was monitored at OD₆₀₀. (B) Culture supernatants were isolated from wild-type, NΔeps, and NΔeps+pEps strains grown in LB broth, LBG (LB with glucose at a 5% final concentration), or LBS and analyzed by SDS-PAGE and silver staining. (C) Culture supernatants and periplasmic fractions of wild-type, NΔeps, and NΔeps+pEps cells grown in LB broth, LBG, or LBS were assayed for the presence of β-lactamase as described in Materials and Methods. The level of β-lactamase in the culture supernatant was expressed as a percentage of the total amount of the enzyme present in both the culture supernatant and cellular extract. The means of at least three independent experiments and corresponding SEM are presented. There was a statistically significant decrease in leakage of β-lactamase to the culture supernatant of NΔeps grown in LBG or LBS medium compared to the leakage of NΔeps grown in LB medium (P < 0.0005).