Sterilization of peat by gamma radiation

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Journal Plant and Soil
Publisher Springer Netherlands
ISSN 0032-079X (Print) 1573-5036 (Online)
Issue Volume 61, Numbers 1-2 / February, 1981
DOI 10.1007/BF02277382
Pages 285-293
Subject Collection Biomedical and Life Sciences
SpringerLink Date Saturday, December 10, 2005

Sterilization of peat by gamma radiation
F. E. Parker1, 2 and J. M. Vincent1, 3

(1)  School of Microbiology, University of New South Wales, Australia
(2)  Present address: Hawkesbury Agricultural College, 2753 Richmond, N.S.W., Australia
(3)  Present address: Department of Microbiology, University of Sydney, 2006, N.S.W., Australia

Received: 10 February 1981  

Summary  The effect of gamma-radiation on the survival of microorganisms has been quantified for the natural
population of two types of peat. Data for several microbial types have been separately determined by regular plating
and by indirect statistical probability estimates including, a wholly enclosed invertedbottle technique for higher dose
levels to exclude any possibility of post-treatment contamination. The most persistent microorganisms at intermediate
dosage (2.5–3.5 Mrad) were commonly a micrococcus (which closely resembled Micrococcus radiodurans) arthrobacter-
like rods, myxobacteria and amoeboid forms. The persistent organisms all survived because of high resistance to -
irradiation, not because of high initial numbers. The most numerous true bacteria (including sporeformers),
actinomycetes, filamentous fungi and yeasts were all readily destroyed. Although the safety margin with the
commercially recommended dose of 5 Mrad is low for some of the more resistant organisms, no change is justified at
this stage since the organisms most likely to survive such a dose do not seem to seriously affect the subsequent growth
and survival of rhizobia. Moreover there would be some risk of radiation-induced peat toxicity if higher doses were
applied and some post-irradiation contamination will be difficult to avoid in commercial production.

Key Words  Gamma radiation - Legume inoculants - Peat - Peat sterilization - Radiation resistant amoebae - Radiation
resistant arthrobacter - Radiation resistant micrococcus - Radiation resistant mycobacteria - Sterility testing