FIG 1.

Effect of pH-treated or heat-treated probiotic spent culture supernatants on growth and pCF10 transfer of E. faecalis. Spent culture supernatants (SCS) of aerobically cultured B. subtilis subsp. natto, B. coagulans, L. reuteri, and L. rhamnosus were first treated with pH adjustment (pH adjusted to 6.5 with NaOH) or heat (80°C water bath for 30 min) and were then added to the E. faecalis mating culture. After a 4-h mating assay, the concentrations of donors, recipients, and transconjugants were determined by plate counting. (A) Effect of pH-adjusted probiotic SCSs. (B) Effect of heat-treated probiotic SCSs. In panels A and B, the concentrations of donors, recipients, and transconjugants are presented as log₁₀(CFU/ml) values. The data are presented as the means ± standard deviations (SDs) (n = 3). (C to F) Effects of untreated, pH-treated, or heat-treated probiotic SCSs on the number of transconjugants per donor (T/D ratios). Each dot in the figure represents a replication. The red diamonds with red lines indicate the means ± SDs (n = 3). Multiple comparisons were evaluated using Duncan’s multiple-range test. The different uppercase letters above the bars or dots indicate the significance of differences between groups (P < 0.05). Ctrl, negative control (the group treated with fresh M9B medium; no SCS treatment); B. sub, B. subtilis subsp. natto; B. coa, B. coagulans; L. reu, L. reuteri; L. rha, L. rhamnosus; NS, no significant difference.