ANi'.\(i(>\isri(' ri;()ri;irrii:s 



221 



measured hy the dihilioii iiicl liods; the aiili- 

 l)i()(if actixitics were dclcnniiUHl hy llic dc- 

 ^\vo of inhibit ion of ri/tltiuni arrhcnonKtncs 

 in cuhurc. Xilroiiicn-rich inalcM-ials, such as 

 rowpca and soybean trash, bloodnical, and 

 tankafiic naxc niai-kcd incrcasos in the ac- 

 tinoniycctc populal ions. The ant ibiot ic indi'X 

 was increased by the use of l)agasse compost 

 and cowpea-soybean trash; a doerease of the 

 antibiotic index occurred, lio\ve\-ei-, when the 

 soil was treated with bonemeal, l)loodmeal, 

 or tankage. Annnonium suU'ate did not ma- 

 terially affect either the ])oi)ulati()n or the 

 antibiotic index. It was suggested that nitro- 

 gen-rich materials, like bloodmeal and tank- 

 age, cause an increase of th(^ nonantagonistic 

 and/or weakly antagonistic actinomycetes in 

 favor of the moderately and highly antago- 

 nistic forms. The cellulosic materials cause 

 an increase of the antagonistic over the 

 nonantagonistic actinomycetes. 



Antagonistic KlTects of Fungi and Bac- 

 teria upon Actinomycetes 



In a natural environment, such as soil, the 

 antagonistic properties of actinomycetes, if 

 they develop at all, will be exerted largely in 

 an aerobic enviroinnent. Under anaerobic or 

 microaerophilic conditions, the actinomy- 

 cetes themselves may be antagonized; l)ac- 

 teria, like Ps. fluorescens, have been shown 

 to exert a marked antagonistic action upon 

 actinomycetes, causing their lysis. B. mcga- 

 ierium can also be antagonistic to certain 

 species of actinomycetes, but also can be 

 antagonized by others. The effect of bacteria 

 upon the potato scab organism was studied 

 in detail h\ Kieszling, who was able to pre- 

 vent scab (le\'elopment in the soil by the use 

 of such bacterial cultures. 



Numerous fungi are also capable of exert- 

 ing a marked destructive effect upon actino- 

 mycetes. This is true, for example, of the ef- 

 fect of the fungus antibiotic penicillin upon 

 human and animal diseases caused by actino- 

 mj^cetes. 



Are Aniiliiol ics Prudiu-ed in the Soil? 



In I!) I."), W'aksman pi'esented e\idence 

 thai il is highly doubtful that ant ibiot ics are 

 produced in the soil itself or that this phe- 

 nomenon is of any great significance in 

 modifying the mici'obiological population of 

 the soil. The exideiice was based upon the 

 following observations: 



(1 ) The fact that an oi'ganisni produces an 

 antibiotic in aitilicial cultui'e is no evidence 

 that is is capable of doing so in soil, pai'ticu- 

 laily since I'elat iAcly small changes in a 

 nutri(Mit medium may fundamentally affect 

 the production of antibiotics in pure culture. 



(2) ]\Iany known antibiotics are extremely 

 unstal)le and could not be expected to re- 

 main vmchanged in soil for sufficient time to 

 have any effect. 



(3) There is no evidence that production 

 of antibiotics affects in any way the survival 

 of organisms producing them. 



(4) The fact that the organisms found in 

 the soil possess no greater resistance to 

 particular antibiotics than comparable 

 strains found in other substrates add further 

 weight to the non-existence of such antibi- 

 otics in soil, in concentrations sufficient to 

 exert an effect. 



Brian, Krassilnikov, and others argued 

 against these assumptions. Brian emphasized 

 that some antibiotics are very stable, that 

 they can be produced locally, where they can 

 have a maximum effect. Siminoff and Gott- 

 lieb (1951, 1952) could demonstrate the for- 

 mation of antibiotics, notably streptomycin, 

 in sterile soil but not in fresh soil. Pramer 

 and Starkey established that streptomycin is 

 rapidly destroyed in the soil. 



Some recent evidence that antil)otics are 

 produced in soil has been submitted by 

 Stevenson (195()). In most cases, llowe^■er, 

 the assumption that the occurrence of 

 streptomyces capable of producing anti- 

 l)iotics will lead to the formation of such 

 antibiotics in soil, and that this will lead to 

 the elimination of pathogenic bacteria is far- 



