A novel bioinformatics strategy for searching industrially useful genome resources from metagenomic sequence libraries

Although remarkable progress in metagenomic sequencing of various environmental samples has been made, large numbers of fragment sequences have been registered in the international DNA databanks, primarily without information on gene function and phylotype, and thus with limited usefulness. Industrial useful biological activity is often carried out by a set of genes, such as those constituting an operon. In this connection, metagenomic approaches have a weakness because sets of the genes are usually split up, since the sequences obtained by metagenome analyses are fragmented into 1-kb or much shorter segments. Therefore, even when a set of genes responsible for an industrially useful function is found in one metagenome library, it is usually difficult to know whether a single genome harbors the entire gene set or whether different genomes have individual genes. By modifying Self-Organizing Map (SOM), we previously developed BLSOM for oligonucleotide composition, which allowed classification (self-organization) of sequence fragments according to genomes. Because BLSOM could reassociate genomic fragments according to genomes, BLSOM may ameliorate the abovementioned weakness of metagenome analyses. Here, we have developed a strategy for clustering of metagenomic sequences according to phylotypes and genomes, by testing a gene set contributing to environment preservation.