Sporichthya polymorpha represents a novel line of descent within the order Actinomycetales

Abstract The 16S rDNA of Sporichthya polymorpha was PCR amplified from genomic DNA and almost completely sequenced using the dideoxy dye-terminator sequencing approach and automated DNA analysis. The primary structure was compared to the homologous molecule from 160 representatives of 37 genera of the order Actinomycetales . No higher similarity than 91.7% was found and the phylogenetic tree shows this morphologically unique organism to from an individual line of descent outside the main radiation of spore- and mycelium-forming organisms.     

Ribosomal RNA and rDNA sequence analyses.

The potential of ribosomal (r) RNA and the encoding genes (rDNA) to elucidate natural relationships has been dramatically extended by improved sequencing approaches and the application of polymerase chain reaction. Sequence information on 16S and 23S rRNA/DNA from 69 strains of 53 Streptomyces species allows determination of regions that can be used as target sites for diagnostic probes, and for amplification and sequencing primers. To generate phylogenetic trees, sequence similarities are converted into distance values. The topologies of the trees based on different parts of the molecule are compared among each other and to the numerical phenotypic clustering of the strains.     

A correlation of phylogenetic diversity in the Proteobacteria with the influences of ecological forces.

The Proteobacteria are physiologically and morphologically diverse, although they form a coherent set of four main lineages on phylogenetic analysis of ribosomal RNA. A rational and consistent taxonomic arrangement bringing today's phenotypic and phylogenetic conclusions about them into register is not yet possible. It is also difficult to understand the selective forces involved in their evolution that fostered such diversity. This latter problem is addressed in this essay and is based on the assumption that bacterial evolution could only have occurred in ecological consortia whose products of metabolism modified the environment, provided nutrition, and have a basis for selection of new capabilities.