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Abstract
SUMMARY: A method of isolating species of Dictyosteliaceae from soil and other substrates is described.
Of ninety-three different strains of bacteria tested as food for Dictyostelium giganteum and D. mucoroides, some were readily or slowly but completely eaten, others were partly eaten and the rest were inedible. No correlation between the edibility of the bacteria and the formation of normal fruiting bodies could be found. More Gram-negative than Gram-positive strains were edible, and non-pigmented bacteria proved more suitable than pigmented bacteria for the normal development of Dictyostelium spp.
Values of pH between 4·1 and 8·9 had no effect on the abundance or on the types of fruiting bodies produced in either D. giganteum or D. mucoroides when suitable strains of bacteria were supplied as food to the myxamoebae on non-nutrient agar.
The maximum dimensions and the form of sorocarps and occasionally the colour of the sori were influenced by the type of bacteria used as food supplies. The influence of the bacterial food supply on the classification of Acrasieae is discussed and one new species (D. giganteum) is described.
Species of Dictyostelium are frequently present in arable soils in Great Britain. The common occurrence of Dictyostelium spp. in soils, which have been unmanured or treated with artificial fertilizers only for 100 years or more, disproves the belief that Dictyostelium spp. are dung organisms.
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