## 2 Results
### Novel sRNAs and Putative Targets
Results indicated that 26 out of 49 sRNAs (i.e., sRNA #5, sRNA #7-13, sRNA #15, sRNA #17, sRNA #19-20, sRNA #29, sRNA #31-35, sRNA #40-41, sRNA #44-49) are highly conserved in many _Streptomyces spp_. (Supplementary Table S9). To search for functional information about these predicted sRNAs, we used IntaRNA software [51; 52]. IntaRNA allowed us to select a total of 241 putative target mRNAs for detected 49 sRNAs (Supplementary Table S10). The results indicated the potential of detected sRNAs to interact with more than one target mRNA. Conversely, there were also cases where a single mRNA is targeted by multiple sRNAs. Most putative targets code for proteins involved in transcription control (including sigma and transcriptional factors). The case of Lrp (AsnC family) transcription factor mRNAs, which are targeted by multiple sRNAs, is noteworthy. IntaRNA predicted three sRNAs (sRNA #5, sRNA #15, sRNA #42) targeting Lrp paralog RS15615, one sRNA (sRNA #23) targeting Lrp paralog RS13995, and one sRNA (sRNA #41) targeting Lrp paralog RS05445 mRNAs. In addition to Lrp, AcrR (Tetk family) transcription factor mRNAs were targeted by several sRNAs. In particular, AcrR (RS05365) mRNA was targeted by sRNA #3, AcrR (RS04560) mRNA by sRNA #8, AcrR (RS14270) mRNA by sRNA #11, and AcrR (RS15315) mRNA by sRNA #49. Among housekeeping functions, the finding of 3 sRNAs may be noteworthy, each of which was predicted to target distinct DNA polymerase III subunits mRNAs (epsilon subunit RS07315, sRNA #2; alpha subunit RS08380, sRNA #3; delta' subunit RS19530, sRNA #3). It may also be relevant to note the presence of one sRNA, sRNA #44, targeting both _int_/C mRNA encoding translation initiation factor IF-1, and _rpsR_ mRNA encoding 30S ribosomal protein S18, while two sRNAs, sRNA #33, sRNA #40, were predicted to target the _asnB_ mRNA coding for asparagine synthetase B (RS16870). A number of sRNAs were predicted to target the transcripts of structural genes involved in cell-wall assembly and morphological development, including two _ssgA_ paralogs (RS07365; RS13975), coding for sporulation and cell division protein SsgA-like, whose transcripts are targeted by two sRNAs (sRNA #28, and sRNA #19, respectively), while the transcript encoding Cps2a (LytR-Cps2A-Psr (LCP) family), an anionic cell wall polymer biosynthesis enzyme, is targeted by sRNA #21 and sRNA #3). sRNA #4 is predicted to target _nanH_ mRNA coding for sialidase. Several sRNAs were predicted to target the transcripts of genes involved in secondary metabolite production including sRNA #2 targeting _wecE_ (RS26695) coding for dTDP-4-amino-4,6-dideoxygalactose transaminase in the spiramycin gene cluster; sRNA #10 targeting _fabH_ (RS34875) coding for 3-oxoacyl-ACP synthase III in a type I PKS gene cluster; sRNA #13 targeting _lanB_ (RS34475) coding for lanthionine biosynthesis dehydratase LanB; and sRNA #14 targeting _alpH_ coding for O-methyltransferase transferase paralogs RS00755 and RS35400 in duplicated alpomycin gene cluster. Regarding the oxidative stress response, one may also note the presence of five sRNAs putatively targeting mRNAs of genes involved in iron and sulfur metabolism, which plays a role in redox balance, including sRNA #3 targeting _soxR_ (RS35165) mRNA, sRNA #7 targeting _hemH_ mRNA coding for prothenro-lyase (ferrochelatase) (RS26415), sRNA #9 targeting _met_C mRNA coding for cystathionine beta-lyase/cystathione gamma-synthase (RS22645), sRNA #36 targeting _mmuM_ mRNA coding for homocysteine/selenocysteine methylase (RS27820), and sRNA #45 targeting mRNA of a gene (RS01550) coding for putative cysteine synthase (RS01550). Overall, these results seem to associate most of _S. ambfaciens_ sRNAs with gene functions involved in the control of mycelial growth, morphological differentiation, secondary metabolism, and stress responses. Indeed, one might note sRNA #2 targeting two paralogs coding for diadenosine tetraphosphate (AP\({}_{4}\)A) hydrolase (RS00910 and RS35245).