Original Articles

Improving the isolation of actinomycetes from soil by high-speed homogenization

Published in: South African Journal of Plant and Soil
Volume 4, issue 4, 1987, pages: 165–170
DOI: 10.1080/02571862.1987.10634967
Author(s): A., A.W. BaeckerDepartment of Microbiology and Plant Pathology, Faculty of Agriculture, Republic of South Africa, K.C. RyanDepartment of Statistics and Biometry, Faculty of Science, Republic of South Africa


Quantitative isolation of actinomycetes from five South African soils with different physical and chemical properties was conducted by hammer-mill comminution followed by high-speed liquid homogenization of resultant soil particles using a shaft homogenizer. Soil homogenates were serially diluted and plated in starch-casein agar and chitin agar for enumeration of isolates. For comparative purposes isolations were also conducted using conventional soil dilution techniques. The results were analysed using a GENSTAT computer program. Analysis showed that homogenization consistently suspended significantly greater numbers of spores from soil particles. Significant differences between magnitudes of actinomycete populations in different soils were also observed. During the initial standardization of the homogenization period required to separate maximum numbers of spores from the soil particles it was found that rates of suspension differed among soils and it is suggested that the particle size distribution and cation exchange capacity in each soil contributed to these differences. Significant differences in the numbers of actinomycetes isolated from different soils were attributed to the amount and nature of the carbon fraction in each soil. It is suggested that comminution, homogenization and dilution plating with appropriate selective culture media could be used to enumerate actinomycetes and other micro-organisms in various substrates not amenable to conventional dilution plating provided the degree of homogenization used is standardized for each new application of the technique.

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