AbstractThe recombinant plasmid pTR‐3 was previously shown to contain part of the 16S and 23S ribosomal RNA genes and the spacer region between the two genes from operon rrnT, from Thiobacillus ferrooxidans. The spacer region was subjected to deletions, using the exonuclease III nested deletions procedure, and the resulting fragments were sequenced. tRNA^ile‐ and tRNA^ala‐like sequences were identified near the 3’ end of16S rRNA gene. The spacer DNAs from both rRNA operons were amplified by the polymerase chain reaction (PCR) and the sequences were compared. No differences were observed. A DNA segment identical to putative box A of the antiterminator sequence of Mycoplasma sp. was identified. Comparison between the sequence of the spacer region from strains Torma and A₄ showed some minor differences. It implies that only in strain A₄ is a recognition site for the Avail restriction enzyme present.