Values are presented as the percentage of intracellular surviving bacteria (CFU mL-1) recovered from macrophages treated with MccJ25 referred to the CFU mL-1 obtained from untreated macrophages. Error bars represent standard deviations from five independent experiments. Figure 2 Effect of macrophage internal environment on S.

Typhimurium sensitivity to MccJ25. 106 mL-1 bacteria harvested from lysed infected RAW 264.7 macrophages and a bacterial suspension JQ1 clinical trial (106 mL-1 cells) in 0.2% Triton X-100 obtained from an LB culture were incubated at 37°C for 6 h with or without 117.5 μM MccJ25. Bars represent the percentage of bacteria surviving MccJ25 treatment CFU ml -1 after growing in LB (grey bar) or within macrophages (dark bar). For each condition, the percentage is referred to the CFU mL-1 obtained with no addition of MccJ25. Error bars represent standard deviations from five independent experiments. Low pH effect on susceptibility of S. Typhimurium to MccJ25 When bacteria replicate within eukaryotic cells, many changes in the membrane are produced in response to the GDC-0068 internal environment. For example, acidic conditions, low magnesium and iron concentrations are some of the host-cell internal conditions to which the bacteria must adapt to [11]. As we observed that MccJ25 affects in vitro the viability of S. Typhimurium previously

replicated within macrophages (Figure 2), we investigated which macrophage environmental condition would allow an unspecific MccJ25 uptake. When bacteria were grown under low magnesium concentration (10 μM) or under iron deprivation (T medium without iron), no Phosphatidylethanolamine N-methyltransferase changes in MccJ25-resistance was observed (Data not shown). On the contrary, when bacteria were cultured with MccJ25 (117.5 μM) in acidic medium (pH 4.7), the number of CFU mL-1 (colony-forming units per milliliter) was 2 orders of magnitude lower than the bacteria grown without the antibiotic, after 24 h (Figure 3). As expected, no antibiotic effect of MccJ25 was observed when pH 7 medium was used in a similar assay (Figure 3). Figure 3

Effect of low pH on S. Typhimurium susceptibility to MccJ25. 106 mL-1 cells of S. Typhimurium 14028s strain were incubated at 37°C in M9 medium pH 7 with (black squares) or without (white squares) 117.5 μM MccJ25 and in M9 pH 4.7 in presence (black triangle) or in absence (white triangle) of 117.5 μM MccJ25. At 0, 6, 8 y 24 h post-treatment, the CFU mL-1 was determined. Error bars represent standard deviations from five independent experiments. Furthermore, we studied the effect of low pH on the sensitivity to MccJ25 of a MccJ25-resistant E. coli strain. For this, we determined the antibiotic sensitivity of MC4100 fhuA::Km strain (mutant in the MccJ25 outer-membrane receptor) in M9 medium plates either at pH 7 or pH 4.7. As expected, this strain became susceptible to the antibiotic at pH 4.7 (MIC = 58.