FIGURE 2: ExDNA accumulates in the medium and produces an inhibitory effect on yeast growth. (A) Quantification of single and double stranded exDNA in EFC and LFC media, during the feeding phases. (B) Stacked bars represent the amounts of single (white) and double (black) stranded exDNA purified from the exhausted medium of EFC, by nine subsequent extractions with HAP. Circles refer to yeast growth in batch cultures with addition of the eluate obtained by each HAP extraction. Cell growth was determined by A₅₉₀ and expressed as percentage of the control. A clear reduction of the inhibitory effect of the eluates is observed with a complete recovery of 100% growth after nine HAP treatments. (C) Effects of exhausted media, exDNA purified from EFC and LFC supernatants and heterologous DNA on yeast growth in batch cultures. Growth was determined by A₅₉₀ after 12 h incubation expressed as percentage of the control. Data refer to mean and standard deviation of 3 replicates. Different letters above bars indicate statistically significant pairwise differences (Tuckey post-hoc test after one-way ANOVA for the effect of treatments on yeast growth). The highest inhibition level is observed for exDNA from EFC medium, whereas no significant inhibitory effect is produced by heterologous DNAs (fish sperm ssDNA, or genomic DNA of C. albicans) and genomic DNA of S.cerevisiae CEN.PK2-1C. A significant recovery of growth was observed when exDNA was pretreated with S1 nuclease, whereas no recovery was found using DNAse.