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|bio method=Hidden Markov Model, Sequence analysis
|bio tech=454, ABI SOLiD, Illumina, Ion Torrent, Sanger
|created by=Bengtsson J, Hartmann M, Eriksson KM, Nilsson RH|created at=University of Gothenburg|maintained=Yes|input format=FASTA|output format=FASTA|language=Perl|licence=GPLv3|os=Linux, Unix, Mac OS X
}}
== Description ==
Megraft is a software tool to graft ribosomal small subunit (16S/18S) fragments onto full-length SSU sequences. Megraft is built upon the notion that when examining the depth of a community sequencing effort, researchers often use rarefaction analysis of the ribosomal small subunit (SSU/16S/18S) gene in a metagenome. However, the SSU sequences in metagenomic libraries generally are present as fragmentary, non-overlapping entries, which poses a great problem for this kind of analysis. Megraft aims to remedy this problem by grafting the input SSU fragments from the metagenome (obtained by e.g. Metaxa) onto full-length SSU sequences. The software also uses a variability model which accounts for observed and unobserved variability. This way, Megraft enables accurate assessment of species richness and sequencing depth in metagenomic datasets.
The algorithm, efficiency and accuracy of Megraft is thoroughly described in a recent paper. It should be noted that this is not a panacea for species richness estimates in metagenomics, but it is a huge step forward over existing approaches.