How does orotic acid affect the growth of R.etli CE3?

Growth inhibition of Rhizobium etli and other organisms by exogenous OA has not been previously reported. We conducted genome-wide transcriptomic analysis to determine the possible mechanism by which OA exerts its growth-inhibitory effect on R. etli CE3. The observed changes fall into several broad categories. First, the decreased expression of genes involved in protein synthesis (including ribosomal genes), replication and energy production indicates that the cells arrest or at least slow their growth, which agrees with the observed growth arrest induced by OA. The upregulation of a key enzyme (PrsAch) for 5'-phosphoribosyl-1'-pyrophosphate (PRPP) synthesis suggests that cells exposed to OA suffer PRPP deprivation. We hypothesized that the PRPP pools were depleted as a result of an increase in the synthesis of OMP stimulated by exogenous OA. PRPP depletion would result in a marked decrease in purine synthesis, which would lead to an imbalance between purine and pyrimidine nucleotides, causing arrest of DNA synthesis and a lack of energetic nucleotides (ADP, ATP). Three independent biological materials with one dyeswap were performed.