FIG. 1.

S. marcescens MB1911 culture filtrates are cytotoxic to HeLa cell monolayers. Culture filtrates prepared from S. marcescens MB1911 and E. coli MB531 were incubated with a monolayer of HeLa cells (4.0 × 10⁴) for 24 h at 37°C. The relative cytotoxicity of each sample was determined versus control cells treated with an equal volume of PBS, as described under Materials and Methods. The data from three separate experiments performed in replicates of at least six were averaged. The error bars indicate standard deviations. P values are reported directly above the data.