BOTANICAL \^EW OF ANTIBIOTICS — JONES 373 



Table 1. — ^The number of actinomycetes present as spores or viable filaments in a gram 

 of soil from several sites in Ann Arbor. These are predominantly in the genus 



Streptomyces. 



8 feet 

 Soil site Top inch 2 feet down 4 U^^ down down 



1 18,100,000 3,493,000 16,850 67 



2 18,600,000 600,000 402,000 2 



3 10,200,000 970,000 214,000 680 



4 13,700,000 1,620,000 31,200 1,770 



5 25,400,000 1,900,000 27,000 10 



6 15,100,000 2,091,000 52,000 6,740 



viomycin, cycloserine, carbomycin, kanamycin, novobiocin, and neomy- 

 cin are representative. Some of these are valuable replacements of 

 penicillin for patients who are sensitive to the latter or where, as is 

 common in staphylococcus infections, the causative organism is resist- 

 ant to penicillin. Many natural products, including antibiotics, are 

 being tested today for possible control of cancer. The Sloan-Kettering 

 Foundation is the center for this research. 



The lower plants responsible for most antibiotics of commerce are 

 members of two unrelated genera, PenicilUum and Streptomyces. 

 The first is a coarse-filamented fungus in which the threads and 

 spores are of the order of 10 microns in diameter. The filaments are 

 clearly cellular with spherical nuclei. They spread, digesting organic 

 materials, and in the fullness of tmie, form a bloom of greenish spores 

 that appear as a powder to the naked eye. Occasionally, under lab- 

 oratory conditions, botanists have observed PenicilUum to reproduce 

 sexually with the formation of a special type of spores, ascospores. 

 This characteristic places the genus with the ascomycete fungi, to 

 which also belong various mildews and even the delectable truffles and 

 morels. 



The actinomycetes, or "actinos," to which the genus Streptomyces 

 belongs, abound everywhere in topsoils where they thrive on plant 

 residues. Table 1 gives a characteristic census of actinomycetes, es- 

 sentially Streptomyces^ per gram of dry soil. A gram corresponds 

 to a "pinch" as used in recipes for baking biscuits. These data were 

 obtained in Ann Arbor at fresh excavations for dwellings in this 

 burgeoning community. The numbers of viable cells which plate out 

 as colonies in the laboratory are seen in the table to decline rapidly 

 the farther down in the subsoil one samples. This is attributable 

 partly to decrease in nutrients (dead leaves, roots, and twigs) but 

 largely to the lack of oxygen. The prevalence of Streptomyces in 

 soils is manifest to all of us in a more direct manner, as the spores are 

 responsible for the pungent, spicy odor of newly turned soil which one 

 can sense while cruising at 90 miles per hour over a country road in 

 springtime. Volatile aromatic substances are wafted from the spores 

 of Streptomyces into the atmosphere. Incidentally, the relatively 

 few "actinos" that occur in the deeper layers of the subsoil are liable to 



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