Use of a computer to group actinomycetes for studies on the ecology of soil microorganisms.

A computer program has been prepared for grouping soil actinomycetes into cluster groups based on the presence or absence of aerial mycelium, the color of soluble pigment, and the shade of color of surface and reverse mycelium. The program automatically condenses cultures with wide ranges of characteristics into a limited number of groups and provides a permanent record so that comparisons can be made among experiments performed over a span of time. The program permits the grouping of large numbers of cultures with minimal laboratory effort and has proven useful in defining some of the ecological factors that lead to changed actinomycete populations in soils.

Studies on the ecology of West Australian actinomycetes: Factors which influence the diversity and types of actionomycetes in Australian soils.

A statistical technique has been employed to study the effects of various environmental factors in altering the actinomycete populations of soils located in the western part of Australia. Over 12,000 actinomycetes obtained at 28 different locations were included in the evaluation. Among factors that had a significant influence were the geographic area at which the sample was taken, the nature of plant rhizosphere, and a rainstorm. Seasonal changes in population did occur, but there was considerable stability of population with time. Although marked differences occurred in types of actinomycetes present among different geographic locations, multiple samples taken within a location at distances of 30 cm or greater showed marked similarity in populations. There were varied degrees of diversity among the populations studied. The population that developed after a rainstorm was low in diversity, whereas the populations of root rhizospheres were as diverse as those of plant-free soil-litter areas. In assessing the ecology of soil actinomycetes, it is important to consider the degree of change in population induced by an environmental factor and also its effect on diversity, since the effects may be complementary or may be opposite in nature.