Analysis of Thermophilic Clades within the Genus Streptomyces by 16S Ribosomal DNA Sequence Comparisons

Abstract

Almost complete sequences of the 16s rRNA genes of eight representative thermophilic streptomycetes were determined following the isolation and cloning of the amplified genes. These sequences were aligned with those of representative mesophilic streptomycetes, and phylogenetic trees were inferred by using four tree-making algorithms. The thermophilic streptomycetes formed two distinct clades that were supported by high bootstrap values based on 1,000 resamplings. One clade encompassed Streptomyces macrosporus and related species, and the second clade included Streptomyces thermudiastaticus and allied taxa. The relationships between the organisms were not markedly influenced by the different tree-making methods, but the rooting of the tree was sensitive to the choice of the outgroup strain. It is evident from this study that the thermophilic streptomycetes do not merit recognition as a distinct taxon within the genus Streptomyces.Most of the emphasis in streptomycete systematics has been focused on mesophilic strains, which grow at temperatures between 15 and 37°C and have optimum temperatures around 25°C. Thermophilic streptomycetes have growth temperature ranges between 28 and 5YC, although cultures of "Streptornyces thennofiscus" and "Streptomyces thennophilus" have been reported to grow at 65°C (45). There is some controversy about whether streptomycetes that grow at 45°C or above should be assigned to distinct taxa or should be considered thermotolerant variants of mesophilic species. Craveri and Pagani (6) proposed the subgenus 7hennostreptomyces for thermophilic strains, but other workers (5, 21) have considered such organisms thermotolerant rather than thermophilic streptomycetes. The name Thennostreptomyces was listed under genera incertae sedis in Beigey's Manual of Determinative Bacteriology, 8th ed. (33).The only comprehensive taxonomic study of thermophilic streptomycetes was carried out by Goodfellow et al. (12), who examined 50 thermophilic, neutrophilic streptomycetes isolated from diverse habitats and representative mesophilic marker strains that had been included in the extensive numerical taxonomic survey of Williams et al. (48). The test strains were screened for 135 unit characters, and the resultant data were analyzed by using three resemblance coefficients and an average-linkage algorithm. In all three analyses, the thermophilic streptomycetes formed a distinct aggregate taxon that encompassed three major clusters (7 to 19 strains), five minor clusters (2 to 3 strains), and two single-member clusters.The three major clusters were equated with Streptomyces megasporus, Streptomyces thermoviolaceus, and Streptomyces thennovulgaris, and one of the minor clusters was equated with Streptomyces macrosporus. The name Streptomyces thermolineatus was proposed for one of the remaining minor clusters. Emended descriptions were given for Streptomyces macrosporus (Krassilnikov et al. 1968) (48), and, with the exception of the Streptomyces albus strains, they formed a second aggregate group.Molecular syst...

A Proposal To Revive the Genus Kitasatospora (Omura, Takahashi, Iwai, and Tanaka 1982)

“…We obtained almost complete 16s rDNA sequences (nucleotides 7 to 1507; E. coli numbering [l]) from all of the organisms described above and subjected them to phylogenetic analyses. The initial analysis, which included sequences from representative species of most actinomycete groups, confirmed that the kitasatosporae and streptomycetes were most closely related to each other in the order Actinomycetales (data not shown) (8,29). We then carried out more detailed analyses in which we focused on sequences from members of the two groups of organisms.…”

Streptomyces thermocoprophilus sp. nov., a cellulase-free endo-xylanase-producing streptomycete.

“…Representatives of these organisms have been distinguished from their better known mesophilic counterparts in numerical phenetic (Goodfellow et al, 1987 ; O'Donnell et al, 1993) and 16S rRNA sequencing studies (D. Kim et al, 1996 ;S. B. Kim et al, 1998 ;.…”

Actinomadura xylanilytica sp. nov., an actinomycete isolated from soil

“…Genomic DNA was extracted from the isolate and PCR amplification and 16S rRNA gene sequencing were achieved using procedures described previously (Kim et al, 1996). The resultant, almost-complete 16S rRNA gene sequence (1454 nt) was aligned manually against corresponding sequences of representatives of the genus Actinomadura retrieved from the EzTaxon database (Chun et al, 2007) using MEGA5 software (Tamura et al, 2011).…”