FURTHER TAXONOMIC STUDIES ON STRAIGHT TO FLEXUOUS STREPTOMYCETES.

Pridham, Thomas G. (Northern Regional Research Laboratory, Peoria, Ill.), and Allister J. Lyons. Further taxonomic studies on straight to flexuous streptomycetes. J. Bacteriol. 89:331-342. 1965.-The best way to handle streptomycete classification, nomenclature, and identification is through application of a genus-species-subspecies concept. To establish a species, principal criteria are morphology of chains of spores and nature of spore-wall surfaces. Subspecies can be differentiated one from another by other criteria, such as chromogenicity, colors of sporulating aerial mycelium and of vegetative mycelium, carbon-utilization patterns, and assessment of qualitative production of antibiotics and sensitivity and resistance to antibacterial antibiotics. A literature study and laboratory studies of some strains suggested that streptomycetes with straight chains of spores could easily be differentiated from those with flexuous chains of spores. An intensive study of about 75 holotype and potential neotype strains indicated that such a differentiation is difficult to accomplish with confidence. Only 19 of the strains had straight chains of spores. These strains are considered, at this time, to be members of the species Streptomyces venezuelae Ehrlich et al. Forty-two of the strains had flexuous chains of spores and were assigned to the species Streptomyces griseus (Krainsky) Waksman and Henrici. Six of the strains had unusual spore-chain morphology. Classic taxonomic procedures allowed the separation of all the strains into a number of categories. The results suggest that more precise information on relationships of strains and qualitative antibiotic production will allow clarification of their sub-specific status. Consideration of the results obtained with strains having aberrant morphology allows some speculation on ranges of variations in morphology that might be encountered with the streptomycetes.