Hi Mohammad

in contrast to bioinformatics side where your question will give an answer, I'm sorry but you can't obtain cDNA or RNA from extracted DNA. in fact, up to date, nobody created the cell machinery to do that....

the best and only way would and will be for you to take the same samples and extract RNA with the adapted kit and protocol.

fred

you need to make rna from the lactobacillus some ideas below :

https://www.researchgate.net/post/Protocol_for_RNA_isolation_from_Lactobacillus_rhamnosus2

and then make cdna from the RNA

You can try to do an in vitro transcription. I'm not sure if this technique will work to your purpose, but is a possibility.

For more details, you can read this paper: Article Synthesis of RNA by In Vitro Transcription

it's more difficult than you think, since introns need to be skipped, the exons frame to be respected, and all the genes transcribed, without forgetting than one gene can produce various RNA...

go back to the samples are extract the RNA to proceed a cDNA, which is more stable than the RNA template.

fred

Thanks a lot to all for valuable suggestions.