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Guo Y,
Zheng W,
Rong X,
Huang Y,
( 2008 ) A multilocus phylogeny of the Streptomyces griseus 16S rRNA gene clade: use of multilocus sequence analysis for streptomycete systematics. PMID : 18175701 : DOI : 10.1099/ijs.0.65224-0 Abstract >>
Streptomycetes are a complex group of actinomycetes that produce diverse bioactive metabolites of commercial significance. Systematics can provide a useful framework for identifying species that may produce novel metabolites. However, previously proposed approaches to the systematics of Streptomyces have suffered from either poor interlaboratory comparability or insufficient resolution. In particular, the Streptomyces griseus 16S rRNA gene clade is the most challenging and least defined group within the genus Streptomyces in terms of phylogeny. Here we report the results of a multilocus sequence analysis scheme developed to address the phylogeny of this clade. Sequence fragments of six housekeeping genes, atpD, gyrB, recA, rpoB, trpB and 16S rRNA, were obtained for 53 reference strains that represent 45 valid species and subspecies. Analysis of each individual locus confirmed the suitability of loci and the congruence of single-gene trees for concatenation. Concatenated trees of three, four, five and all six genes were constructed, and the stability of the topology and discriminatory power of each tree were analysed. It can be concluded from the results that phylogenetic analysis based on multilocus sequences is more accurate and robust for species delineation within Streptomyces. A multilocus phylogeny of six genes proved to be optimal for elucidating the interspecies relationships within the S. griseus 16S rRNA gene clade. Our multilocus sequence analysis scheme provides a valuable tool that can be applied to other Streptomyces clades for refining the systematic framework of this genus.
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2. |
Han JH,
Cho MH,
Kim SB,
( 2012 ) Ribosomal and protein coding gene based multigene phylogeny on the family Streptomycetaceae. PMID : 22154623 : DOI : 10.1016/j.syapm.2011.08.007 Abstract >>
The phylogenetic relationship among the three genera of the family Streptomycetaceae was examined using the small and large subunit ribosomal RNA genes, and the gyrB, rpoB, trpB, atpD and recA genes. The total stretches of the analyzed ribosomal genes were 4.2kb, and those of five protein coding genes were 4.5 kb. The resultant phylogenetic trees confirmed that each genus formed an independent clade in the majority of cases. The G+C contents of rRNA genes were 56.9-58.9 mol%, and those of protein coding genes were 65.4-72.4 mol%, the latter being closer to those of the genomic DNAs. The average nucleotide sequence identity between the organisms were 94.1-96.4% for rRNA genes and 85.7-90.6% for protein coding genes, thus indicating that protein coding genes can give higher resolution than rRNA genes. In addition, the protein coding gene trees were more stable than the rRNA gene trees, supported by higher bootstrap values and other treeing algorithms. Moreover, the genome data of six Streptomyces species indicated that many protein coding genes exhibited higher correlations with genome relatedness. The combined gene sequences were also shown to give a better resolution with higher stability than any single genes, though not necessarily more correlated with genome relatedness. It is evident from this study that the rRNA gene based phylogeny can be misleading, and also that protein coding genes have a number of advantages over the rRNA genes as the phylogenetic markers including a high correlation with the genome relatedness.
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