In eubacteria, the rpsB-tsf operon encodes two essential components of translational apparatus, ribosomal protein (r-protein) S2 and elongation factor Ts. Recently, we located the promoter region of the Escherichia coli rpsB-tsf operon and demonstrated that both rpsB and tsf genes are negatively regulated by r-protein S2 at the translational level. In this paper, we present data of phylogenetic analysis showing high conservation of both the promoter signature and the structure of the 5'-untranslated region (5'-UTR) of the rpsB mRNA in gamma-proteobacteria. Despite the difference in length and overall primary structure of the rpsB 5'-UTRs for various representatives of this bacterial phylum, several short regions within the 5'-UTRs appeared to be universally conserved, implying their participation in the expression regulation. Phylogenetic predictions have been experimentally confirmed. We show here that the presumable rpsB promoter regions from Yersinia pestis, Haemophilus influenzae and Pseudomonas aeruginosa are able to drive transcription of the lacZ -reporter in E. coli and that the corresponding rpsB 5'-UTRs are subjected to autogenous repression by r-protein S2 in vivo.