When the ΔagaA ΔnagA double knockout mutant strains of EDL933 and E. coli C were examined for growth on GlcNAc and Aga it was found that both strains did not grow on GlcNAc as expected but importantly,
these mutants also did not grow on Aga (Figures 2A Selleckchem GDC-0994 and 2B). These results indicate that agaA is not essential for Aga utilization because nagA can substitute for agaA and therefore the presence of either agaA or nagA is sufficient for Aga utilization. Figure 2 Growth of EDL933, E. coli C, and their mutants on Aga and GlcNAc. EDL933, E. coli C, and the indicated knockout mutants derived from them were streaked out on MOPS minimal agar plates containing Aga (A) and GlcNAc (B) and incubated at 37°C for 48 h. The description of the strains in the eight sectors of the plates is indicated in the diagram below (C). Quantitative real time RT-PCR analysis reveal that nagA and nagB are expressed in ΔagaA mutants grown on Aga To investigate if NagA is induced in ΔagaA mutants when grown on Aga we examined the relative expression levels of agaA and nagA in wild type, ΔagaA, and ΔnagA strains of EDL933 and E. coli C grown on BX-795 price different carbon sources by qRT-PCR. The expression
of the agaS gene was also examined as a second gene of the aga/gam regulon that is under the control of the second promoter, Ps, and similarly nagB was chosen as a second gene of the nag regulon. Relative expression selleck chemicals llc levels of genes in wild type and mutant strains of EDL933 and E. coli C grown on Aga and GlcNAc were calculated with respect to that of the expression of the corresponding genes in wild type strains grown on glycerol. As shown in Table 1, growth on Aga induced agaA and agaS about 375 and 500-fold, respectively, in
EDL933 and about 30 and 60-fold, respectively, in E. coli C. The nagA and nagB genes were not induced by Aga in either strain. Growth on GlcNAc induced nagA and nagB about 12 and 24-fold, respectively, in EDL933 and 16 and 23 fold, respectively, in E. coli C. In presence of GlcNAc, agaA and agaS were not induced in EDL933, but in E. coli C the induction was minimal, which is less than 10% of that in Aga grown cells. In Aga grown cells the induction of agaA and agaS was about Metalloexopeptidase 12 and 8-fold higher, respectively, in EDL933 than in E. coli C but the levels of induction of nagA and nagB in both strains grown on GlcNAc were comparable (Table 1). Earlier studies using single copy lysogenic derivatives of E. coli K-12 harboring Pz- lacZ and Ps-lacZ transcriptional fusions showed that the Pz and the Ps promoters were induced 5 and 20-fold, respectively, upon growth on Aga in minimal medium containing 0.2% casamino acids but growth in GlcNAc did not induce expression from these promoters .