soil and rhizosphere meta-transcriptome samples
The predominance of rRNAs in the transcriptome is a major technical challenge in sequence-based analysis of cDNAs from microbial isolates and communities (Frias-Lopez, et al., 2008, Gilbert et al., 2008, He et al., 2010 Poretsky et al., 2009, Stewart et al., 2009, Urich et al., 2008). In order to get rid of rRNA and amplify mRNA, the ExpressArt Bacterial mRNA Amplification Kit (AmpTec), was used. This kit has strong selection against rRNA, due to TRinucleotide primer, which does not bind to secondary structures of rRNA. Removal efficiency and RNA quality was evaluated using a 2100 Bioanalyzer (Agilent), kindly provided by the Microarray Unit of Bar-Ilan University. the removal of rRNA has reached more then 90%. The RNA Integrity Number (RIN) estimates the quality of RNA. Values up to 7 are considered good for RNA purified from pure culture.    The resulting amplified mRNA was converted into ds cDNA by Add-On ds DNA synthesis. In the following tables (Table 2, Table 3) there is summarized data of the amounts of Total RNA and amplified mRNA used for cDNA conversion and how much cDNA obtained in each sample. The size distribution of the ds cDNA length, received in the PCR reaction with primers supplied by AmpTec, is presented in  Figure 3. The ds cDNA samples were sent for 454-Sequencing analysis performed at the Research and Testing Laboratories (Lubbock, TX, USA)