FIG. 4.

Involvement of the frz operon in the survival of strain BEN2908 during the late stationary phase of static growth. (A and C) Strains BEN2908 and BEN2908 Δfrz::kan were inoculated in equivalent numbers into LB medium containing nalidixic acid. These cultures were incubated at 37°C without (A) or with (C) agitation. The cultures were measured at OD₆₀₀, and growth curves were traced. The proportion of strain BEN2908 Δfrz::kan in the cultures was analyzed during 336 h. (B) Cocultures were incubated for 168 h without agitation in a minimal medium containing different carbohydrates as the sole carbon source (A, glucose; B, mannitol; C, mannose; D, 3-O-β-d-galactopyranosyl-d-arabinose; E, d-fructose; F, l-fructose; G, d-psicose; H, l-psicose; I, d-sorbose; J, l-sorbose; K, d-tagatose; and L, l-tagatose). Results are presented as means ± standard deviations for three independent cocultures. Growth in minimal medium was estimated by measuring the OD after 168 h (−, OD₄₅₀ = 0.07; ±, OD₄₅₀ = 0.35; +, OD₄₅₀ = 0.6). The proportion of the mutant in the inoculum (starting ratio) is represented by the dotted line. The standard deviation of the inoculum ratio is less than 5%. The significance of the difference between the proportion of the mutant in the inoculum and during culture was tested with the Student t test (*, 0.05 > P > 0.02; **, 0.02 > P > 0.01; ***, P < 0.001).