By definition, chimeric RNAs consist of transcript fragments from different genes. In eukaryotes, they are formed as trans-splicing products, some of which have already been recognized as biomarkers of pathological states. Fused RNAs have also been detected in bacteria, where intermolecular recombination is rare, though it remains an open question whether they are biologically significant products or sampling artifacts. Recently, we identified unusual chimeric RNAs in Escherichia coli containing uniform 8(9)-mers GCCAAGGC(G) at the 5’-end. We hypothesized that such conjunctions may arise due to the ability of 8/9-mers to prime transcription at promoters or resume RNA synthesis from stalled transcription complexes. Here, we analyzed 34 RNA-seq datasets, obtained on different sequencing platforms, and identified 560 types of modified oligonucleotides, with nearly 50% varieties coming from rRNAs (23.1%) and tRNAs (23.2%). Assessment of recurrently and incidentally modified RNAs revealed non-template cgttCCCGTGG 5’-motifs. Although being significantly less frequent, their existence suggests that GCCAAGGC(G)-mediated terminal modifications are not an exceptional phenomenon. We also identified 804 canonical chimeras formed alternatively with the 14 selected targets of GCCAAGGC(G), 62.2% of which included rRNA fragments. Observing that exogenous 9-mers increase the percentage of terminal extensions, we suggest that E. coli implements a mechanism of co-transcriptional modifications distinct from classical chimerization with a predominant selectivity for the 5’-ends of tRNAs.