In the tolC mutant we observed an increased expression of rbfA and rimM, coding for a ribosome binding factor and an rRNA-processing protein, respectively. Both gene products are essential for efficient processing of 16 S rRNA in E. coli . The rrmJ gene encoding a ribosomal RNA large subunit
methyltransferase and genes ksgA and hemK1 encoding two methylases involved in quality control by the small subunit of the ribosome  and methylation of release factors , respectively, also showed increased expression in the tolC mutant. Concerning amino acyl-tRNA modification we observed increased expression of the trmFO gene encoding a folate-dependent tRNA methyltransferase in the tolC mutant (Table 1). Maturation of tRNA precursors into functional tRNA molecules requires trimming of the primary transcript at both the 5′and 3′ends and is check details catalyzed by RNase P and RNase PH. Expression of genes encoding RNase P (rnpA) and RNase PH (rph), and genes encoding Rnase D (rnd1 and rnd2) which contribute to the 3′maturation of several stable RNAs also displayed increased expression levels in the tolC mutant. In contrast to S. meliloti cells exposed to osmotic stress
which showed decreased expression of genes involved in protein metabolism [30, 31], tolC mutant cells showed increased expression of these genes. As mentioned previously, a plausible explanation would be the need for new proteins to replace denatured ones due to oxidative stress conditions and the higher selleck inhibitor levels of metabolic enzymes needed for the cell to produce energy. Genes involved in energy and central intermediary metabolism We found increased expression of multiple genes involved in central metabolism and energy production in the tolC mutant (Fig. 5), suggesting a higher metabolic rate in response to tolC gene mutation. Anidulafungin (LY303366) For instance, genes encoding 11 out of 12 of the enzymes involved in the tricarboxylic acid cycle (TCA) (acnA,
icd, sucABCD, lpdA1A2, sdhABCD, fumC and mdh), along with genes encoding many enzymes of the Calvin-Benson-Bassham reductive pentose phosphate pathway (rbcL, pgk, fbaB, cbbF, tkt2, cbbT, rpiA and rpe) and most genes encoding enzymes for the glycolysis and gluconeogenesis pathways (cbbF, fbaB, tpiA1, gap, pgk, eno, pdhA) had significantly increased expression (Fig. 5). Alongside the increased expression of the genes encoding TCA enzymes, all genes encoding different protein complexes in the respiratory chain had also an increased expression. Genes include nuoA1B1C1D1E1F1G1HIJK1LMN and ndh forming NADH dehydrogenase (complex I); sdhABCD from fumarate reductase (complex II); fbcBCF from cytochrome c reductase (complex III); ctaCDEG and SMc01800 from cytochrome c oxidase (complex IV); and atpCDGABEF2FH from ATP synthase (complex V) (Table 1).