The autogenous regulation of ribosomal protein (r-protein) synthesis plays a key role in maintaining the stoichiometry of ribosomal components in bacteria. In this work, taking the gene as a classic example, we addressed for the first time the in vivo regulation of r-protein synthesis in the mycobacteria () and (). We used a strategy based on chromosomally integrated reporters under the control of the regulatory regions and the ectopic expression of S15 to measure its impact on the reporter expression. Because the use of   as a host appeared inefficient, a fluorescent reporter system was developed by inserting or   fusions into the chromosome and expressing S15 or S15 in trans from a novel replicative shuttle vector, pAMYC. The results of the eGFP expression measurements in cells provided evidence that the gene in and was feedback-regulated at the translation level. The mutagenic analysis showed that the folding of   5'UTR in a pseudoknot appeared crucial for repression by both S15 and S15, thus indicating a striking resemblance of the feedback control in mycobacteria and in .