GROUPS AM) SPECIES 01 GEN1 S STREPTOMYCES 



'.'7 



XV. Aerial mycelium gray; substrate my- 

 celium blue-violel or red-brown. 

 Series Violaceus 



6. PRIDHAM, HESSELTINE, AM) BENEDICT 



system (1957, L958) 



Id their earlier system, these invesl igators 

 divided the genus Streptomyces into seven 

 groups. Each group was characterized by a 

 distind morphology of the sporophores in 

 mature cultures, and by a distind color of 

 the aerial mycelium. This system subse- 

 quently was revised. Morphological sections 

 and color series were established and, on the 

 basis of literature study and laboratory in- 

 vestigations, many species and known anti- 

 biotic-producing strains were cataloged. It 

 was suggested thai evaluation of the compo- 

 nent strains in the sections and series, by 

 physiological tests, would allow the deter- 

 mination of ranges of variation and a more 

 logical approach to speciation in the genus. 

 The placement by these investigators of 

 strains in morphological sections, regardless 

 dt' species designation, has suggested synon- 

 ymy, as well as misident ilicat ion of many 

 strains. 



The following bases were considered in 

 justifying these subdivisions: 



1. The morphology of the sporophores of 

 a particular si rain does not appreciably 

 change on substrata that supporl optimal 

 formation of aerial mycelium, sporophores, 

 and spores. Morphological patterns exhibited 

 by streptomycetes ate not subject to con- 

 siderable variation, unless degeneration of a 

 particular strain has occurred through im- 

 proper maintenance. Morphological exami- 

 Dations should be made after two weeks' 

 incubation at 28 30°C on several appropriate 

 media. 



2. The color of the sporulating aerial my- 

 celium of a given st rain at maturity was said 

 not to differ appreciably from medium to 

 medium. Each morphological section of the 

 genus can he further subdivided into color 

 "series." Each color series can he subdivided, 



on the basis of physiological criteria, into 

 "species." Additional delineation can then 

 he w^vil to create "varieties" or "physiolog- 

 ical forms," if need he. 



:'». The present concept of the genus 

 Streptomyces is interpreted rather broadly. 

 Some of the strains identified as members of 

 the genus may in reality belong in other 

 genera. 



The proposed section- were designated as 

 follows: 



I. Rectus-flexibilis (MY). Sporophores 

 straight, flexuous, or fascicled; mi 

 spirals. Type species S. griseus. 

 II. Retinaculum-apertum (HA). Sporo- 

 phores in 1 he form of hooks, open loops, 

 or greatly extended spirals. Type 

 species S. fradiae. 



III. Spira (S). Sporophores either shorl and 

 gnarled, or in the form of compad 

 spirals or of extended long and open 

 spirals. Type species S. viridochro- 

 mogenes I fig. 26). 



IV. Monoverticillus (MV). Sporophores in 

 the form of primary verticils attached 

 to long, straight branches; no spirals. 



Y. Monoverticillus-spira (MV-S). Sporo- 

 phores as primary verticils attached to 

 long, straight branches; elements of 

 verticils spiraled. 

 \"i. Biverticillus (BV). Sporophores as com- 

 pound verticils attached to long, 

 straighl branches; no spirals. Type 

 species S. cinnamomi us f. cinnamonu us. 

 VII. Biverticillus-spira (BIV-S). Sporo- 

 phores as compound verticils attached 

 to long, straight branches; element- of 

 secondary verticils spiraled. 

 In addition lo the above sections, another 

 section was set np lo include .-train- for 

 which no micromorphological data were 

 available. 



Each '•section" was subdivided into 

 "series" based on the color of sporulating 

 aerial mycelium at maturity. The proposed 

 series were designated as follows: 

 I. White. 



