Phylogenetic Analysis of Type I and Type II Polyketide Synthase from Tropical Forest Soil

Culture-independent approach was employed to retrieve diverse type I and type II polyketide synthase (PICS) ketosynthase (KS) domains from community DNA extracted from forest topsoil. Type I KS domains detected were from four phyla which comprised Cyanobacteria, Proteobacteria, Actinobacteria, Chloroflexi and uncultured bacteria. The type IIKS alpha domains were derived from four suborders of actinobacteria in addition to uncultured bacteria. Approximately 25% of the KS domains were recovered from uncultured bacteria and many sequences of type I KS were derived from Myxobacteria. BLASTP results showed that the type I and type II KS domain amino acid sequences were between 52 to 93% identical to the comparative sequences in the GenBank database. Phylogenetic analysis for novelty prediction of KS domains showed 14 and 9 novel clades of type I KS and type II PKS KS alpha domains, respectively. These phylogenetically distinct novel clades might represent a new subclass of KS domains. Present data suggests the possibility of further discovery of novel genes encoding bioactive compounds which may have medical and pharmaceutical value.