Transfer of Elytrosporangium brasiliense Falcão de Morais et al., Elytrosporangium carpinense Falcão de Morais et al., Elytrosporangium spirale Falcão de Morais, Microellobosporia cinerea Cross et al., Microellobosporia flavea Cross et al., Microellobosporia grisea (Konev et al.) Pridham and Microellobosporia violacea (Tsyganov et al.) Pridham to the Genus Streptomyces, with emended descriptions of the species

Genome-based analyses reveal heterotypic synonyms of Streptomyces species and associated subspecies

In the genus Streptomyces, several validly described species have been reduced to synonyms of earlier described species though additional synonyms remain to be detected given the previous dependence on traditional phenotypic methods. In this study, genome-based procedures, including DNA-DNA hybridization analyses, overall genome-related indices, such as ANI, dDDH and AAI, revealed that certain strains recorded genomic indices above the threshold values used to define species boundaries. The results of phylogenetic and phylogenomic trees based on concatenated and phylogenomic analyses showed that 33 out of 364 tested species could be assigned to 15 species groups and that 18 Streptomyces species names be reclassified as later heterotypic synonyms of earlier validly published species. Consequently, it is proposed that S. albaduncus is a later heterotypic synonym of S. griseoloalbus; S. bellus is a synonym of S. coeruleorubidus; S. gancidicus and S. rubiginosus are synonyms of S. pseudogriseolus; S. niveoruber is a synonym of S. griseoviridis; S. griseomycini is a synonym of S. griseostramineus; S. jietaisiensis is a synonym of S. griseoaurantiacus; S. pluricolorescens is a synonym of S. rubiginosohelvolus; S. nashvillensis is a synonym of S. tanashiensis; S. yerevanensis is a synonym of S. flaveus; S. durhamensis is a synonym of S. filipinensis; S. recifensis is a synonym of S. griseoluteus; S. canaries and S. olivaceoviridis are synonyms of S. corchorusii; S. melanosporofaciens is a synonym of S. antimycoticus; S. albulus is a synonym of S. noursei; and S. janthinus and S. violarus are synonyms of S. violaceus. Additionally, seven of these 18 Streptomyces species have been designated subspecies.

Streptomyces cupreus sp. nov., an antimicrobial producing actinobacterium isolated from Himalayan soil

A novel actinobacterium, designated Streptomyces sp strain PSKA01^T, was isolated from a soil sample of Kashmir Himalaya, India (latitude:34˚-01'N; longitude:74˚-47'E; altitude: 5328 ft). The taxonomic position of this strain was revealed by a polyphasic approach. Comparative analysis of the 16S rRNA gene sequences indicated that PSKA01^T was closely related to the members of the genus Streptomyces, with the highest similarity to Streptomyces venetus CMU-AB225^T (99.3%), Streptomyces levis NBRC 15423 ^T (99.3%), Streptomyces misionensis DSM 40306 ^T (99.2%), Streptomyces carpinensis NRRL B-16921 ^T (99.2%), Streptomyces purpurascens NBRC 13077 ^T (99.2%), and Streptomyces phaeoluteichromatogenes NRRL 5799 ^T (99.2%). A phylogenomic tree based on genome sequences of the isolated strains, conferred by Type Strain Genome Server (TYGS), separated them from rest of the Streptomyces. The cell wall contained LL-diaminopimelic acid and the whole-cell hydrolysates were xylose and rhamnose. Major fatty acid methyl esters (FAME) were observed as 16:0 iso and 17:0 anteiso. In addition to the differences in phenotypic characters, the average nucleotide identity (ANI), average amino acid identity (AAI), digital DNA-DNA hybridization (dDDH) values, tetranucleotide frequency correlation coefficient (TETRA), and multilocus sequence analysis (MLSA) between PSKA01^T and closely related type strains were considerably lower than the recommended threshold value; therefore, this isolate represents a novel Streptomyces species, for which the name Streptomyces cupreus sp. nov. is proposed. The type strain is PSKA01^T (= JCM 33752 ^T = MCC 4182 ^T).

Phylogenetic study of the species within the family Streptomycetaceae

Species of the genus Streptomyces, which constitute the vast majority of taxa within the family Streptomycetaceae, are a predominant component of the microbial population in soils throughout the world and have been the subject of extensive isolation and screening efforts over the years because they are a major source of commercially and medically important secondary metabolites. Taxonomic characterization of Streptomyces strains has been a challenge due to the large number of described species, greater than any other microbial genus, resulting from academic and industrial activities. The methods used for characterization have evolved through several phases over the years from those based largely on morphological observations, to subsequent classifications based on numerical taxonomic analyses of standardized sets of phenotypic characters and, most recently, to the use of molecular phylogenetic analyses of gene sequences. The present phylogenetic study examines almost all described species (615 taxa) within the family Streptomycetaceae based on 16S rRNA gene sequences and illustrates the species diversity within this family, which is observed to contain 130 statistically supported clades, as well as many unsupported and single member clusters. Many of the observed clades are consistent with earlier morphological and numerical taxonomic studies, but it is apparent that insufficient variation is present in the 16S rRNA gene sequence within the species of this family to permit bootstrap-supported resolution of relationships between many of the individual clusters.

Classification of Streptomyces griseus (Krainsky 1914) Waksman and Henrici 1948 and related species and the transfer of ‘Microstreptospora cinerea’ to the genus Streptomyces as Streptomyces yanii sp. nov

A soil actinomycete, strain 80-133T, with the non-validly published name ‘Microstreptospora cinerea’, was the subject of a polyphasic study designed to clarify its taxonomic status. Comparative 16S rRNA gene sequence studies indicated that the organism belonged to the genus Streptomyces, a result in line with previous chemotaxonomic and morphological data. The strain belonged to the Streptomyces griseus clade, but could be distinguished from representatives of species assigned to this taxon by using DNA–DNA relatedness and phenotypic data. In light of these findings, it is proposed that the organism should be recognized as a novel species of the genus Streptomyces. The name proposed for this taxon is Streptomyces yanii sp. nov., with isolate 80-133T (=AS 4.1146T=JCM 3331T) as the type strain. It was also shown that representative strains of Streptomyces argenteolus, Streptomyces caviscabies, S. griseus and Streptomyces setonii belong to the same genomic species and have key phenotypic properties in common. It is proposed that S. caviscabies and S. setonii should be considered as later heterotypic synonyms of S. griseus and that S. argenteolus AS 4.1693T should also be assigned to this taxon.

The medically important aerobic actinomycetes: epidemiology and microbiology

The aerobic actinomycetes are soil-inhabiting microorganisms that occur worldwide. In 1888, Nocard first recognized the pathogenic potential of this group of microorganisms. Since then, several aerobic actinomycetes have been a major source of interest for the commercial drug industry and have proved to be extremely useful microorganisms for producing novel antimicrobial agents. They have also been well known as potential veterinary pathogens affecting many different animal species. The medically important aerobic actinomycetes may cause significant morbidity and mortality, in particular in highly susceptible severely immunocompromised patients, including transplant recipients and patients infected with human immunodeficiency virus. However, the diagnosis of these infections may be difficult, and effective antimicrobial therapy may be complicated by antimicrobial resistance. The taxonomy of these microorganisms has been problematic. In recent revisions of their classification, new pathogenic species have been recognized. The development of additional and more reliable diagnostic tests and of a standardized method for antimicrobial susceptibility testing and the application of molecular techniques for the diagnosis and subtyping of these microorganisms are needed to better diagnose and treat infected patients and to identify effective control measures for these unusual pathogens. We review the epidemiology and microbiology of the major medically important aerobic actinomycetes.

Numerical classification and identification of Streptomyces species--a review

Evidence is presented to show that numerical taxonomy is of proven value both for the circumscription and identification of Streptomyces species. In addition, 252 representatives of numerically defined species and species-groups of this taxon were examined for 273 unit characters and the resultant data analysed using conventional statistics. Clustering was only marginally affected by the proximity coefficients used or by test error, estimated at 3.37%. The numerical classification obtained confirmed and extended the results of previous taxometric surveys, notably by showing that the Streptomyces albidoflavus species-group encompassed taxospecies corresponding to S. albidoflavus, Streptomyces anulatus and Streptomyces halstedii. Rapid enzyme tests based upon the fluorophores, 7-amino-4-methylcoumarin and 4-methylumbelliferone, provide useful data for streptomycete systematics. It can be concluded that the genus Streptomyces is currently well circumscribed and underspeciated.