Comparison of metabolite and gene expression profiles of C. perfringens grown with cystine or homocysteine To obtain new insights into the regulation in response to sulfur availability, we compared the metabolome and the transcriptome of C. perfringens after growth in the presence of 0.5 mM cystine or 1 mM homocysteine. The doubling time was about two-fold higher for C. perfringens strain 13 grown in the presence of homocysteine than in the presence C646 concentration of cystine. Cystine allows efficient growth while homocysteine is a poor sulfur source for C. perfringens. This suggests that some metabolites are limiting during growth with homocysteine. So, we measured the

intracellular concentration of several sulfur compounds and amino acids by HPLC in crude extracts of strain 13 grown in the presence of cystine or homocysteine

(Fig. 3). The intracellular concentration of methionine remained undetectable learn more in both growth conditions. This suggests that methionine biosynthesis is not very efficient and/or that methionine requirements are high. Homocysteine can be detected only during growth with this compound suggesting that homocysteine was mainly taken up from outside under these conditions. Cystine, cysteine but also proline pools were below the threshold of detection during growth with homocysteine while their intracellular concentrations Adenosine triphosphate were 325 μM, 236 μM and 80 μM, respectively during growth with cystine. This strongly suggests that growth in the presence of homocysteine mimics conditions typically associated with cysteine limitation.

The concentration of alanine, lysine and serine and/or threonine differed to a lesser extent in these two conditions. Figure 3 Intracellular concentration of sulfur compounds (A) and amino acids (B) in strain 13 grown in the presence of cystine or homocysteine. Grey or white boxes indicate the metabolite concentrations extracted from strain 13 grown in the presence of 0.5 mM cystine or 1 mM homocysteine, respectively. The mean value of three independent experiments is presented. # indicates that the metabolite is not detectable. We further compared gene expression profiles of strain 13 grown in the presence of cystine or homocysteine. For this purpose, we designed a microarray containing oligonucleotides representative of 2706 genes of C. perfringens. For each condition, eight data sets generated with RNAs extracted from four independent cultures were used to Everolimus perform statistical analysis (see Methods). A total number of 177 genes were differentially expressed in these two conditions. Most of them (122 out of 177) were up-regulated in the presence of homocysteine. Some of the controlled genes including those associated with sulfur metabolism, redox functions, carbon metabolism and virulence are presented in Table 1.