[mg-rast] Help taxonomic classification

I'm doing a bioinformatic project and I have a large excel file, containing a large amount of annotated sequences (with the five most similar hits for each) that were obtained from root-soil samples. (I have also the file contigs.fasta) Since there are sequences of all taxonomic groups (Plant, Animal, Fungi, bacterial, protist) i would like to find some software application that could discriminate between sequences from each taxonomic group. How can i do this? Do you know? can you advise me some person knowing this kind of things? Inês Martins University of Minho Portugal