Yes, you can use a mixture of oligo (dT) and random hexamers. This is fairly common in several cDNA synthesis kits. However, the oligo(dT) only primes the poly-A tail of mRNAs, which is not present in bacterial RNA (actually whenever polyadenilation is present it promotes degradation of bacterial RNA, the opposite effect of what polyadenilation does to eukaryotic RNA). If you are not using a cDNA synthesis kit random hexamers is the way to go.

If your main goal is to isolate mRNA there are RNA extraction kits designed to enrich for mRNA by removing small RNAs.

yes, you can. I had used an oligo dT and a random primer together for the cDNA synthesis. The yield is better that way.

Sure you can, but remember that Oligo(dT) primer will amplify only mature mRNA and hexamers will amplify randomly also imature RNA. This is important in eukaryotic systems which is probably not your case.

Thank you very much for you suggestions. I not sure that how much should I add from each primer If I start synthesis with 2µg/µlRNA? does it makes problem if I add more random hexomer or oligo (dT) for cDNA synthesis?

You should check that the kind of cDNA that you get with random hexamers is OK for the purpose of your experiment. In other words what are you going to do with the cDNA? Random hexamers protocols tend to amplify a pool of shorter scattered along the gene but with the 3' end less represented than with oligo (dT)x.

Yes, you can use a mixture of oligo (dT) and random hexamers. This is fairly common in several cDNA synthesis kits. However, the oligo(dT) only primes the poly-A tail of mRNAs, which is not present in bacterial RNA (actually whenever polyadenilation is present it promotes degradation of bacterial RNA, the opposite effect of what polyadenilation does to eukaryotic RNA). If you are not using a cDNA synthesis kit random hexamers is the way to go.

If your main goal is to isolate mRNA there are RNA extraction kits designed to enrich for mRNA by removing small RNAs.

In our lab we use random hexamers at a final concentration of 5 µM for 2-5 µg of RNA.

Actually I want o compare gene expression of Bacillus bacteria at two different concentration treatment and I am planing to use SSH (Subtractive Suppression Hybridization) kit but this kit containing only oligo (dT) primers and I was thinking that bacteria does not produce much mRNA that is why I thought random hexomer also should be used.

Bacterial mRNA is not poly-adenylated. Therefore not a good plan to use oligo dT primer!

As several people have pointed out you can't use oligo dT primers on bacterial DNA. But if your can cycle the PCR and hybridisation steps, then you shouldn't have too many problems, as you can greatly increase the amount of material at this point.

Hi Abdugaffar

I agree with Angel Casanova-Torres

To some extent, I agree with Samujjwal. However, it is easily said than done. This is a cautionary note for you as you have rightly pointed out that bacteria do not contain so much of mRNA.

I guess both primer works at slightly different conditions, so rather than using both primer in the same reaction mixture, use two different reaction mixtures in small liquid and after reaction done mix them.