A nonobligate, bacterial predator of bacteria in soil is described. It was previously designated as strain N-1. It is a gram-negative, aerobic, mesophilic, short rod that multiplies by binary fission. It is motile and has peritrichous flagella. It has simple nutritive requirements when not acting as a predator. Glucose is not utilized as a carbon source. Instead, it uses fructose or any of several amino acids. As a predator, it attacks both gram-positive and gram-negative bacteria, including certain other nonobligate bacterial predators of bacteria in soil. It is highly resistant to copper, and its growth initiation is strongly stimulated by copper. Copper has no effect on the cellular multiplication that occurs after growth has initiated. A new genus, Cupriavidus, is proposed for this bacterium. The type species is Cupriavidus necator sp. nov., and strain N-1 (ATCC 43291) is the type strain of this species.

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An isolation method for actinoplanetes is described which uses the ability of the sporangium to withstand desiccation and release motile spores when subsequently rehydrated. The desiccation stage reduces the number of associated Gram negative bacteria which cause problems when attempts are made to isolate species on agar plates from natural substrates. The method has enabled the isolation of actinoplanetes directly from soil and plant litter and indirectly from soil with the aid of baits such as pollen and hair. Actinoplanetes appear to be common in dry soils collected from arid areas and sand dune systems. They are normally present on leaves submerged for a time in rivers, streams and lakes and subsequently deposited in heaps on shores or as debris on overhanging vegetation. An actinomycete resembling the ‘spore‐dome’ organism recovered from leaves and twigs by Willoughby (1969) was frequently isolated during the course of these studies. Preliminary work suggests that different species can be recognized and could constitute a new genus within the family Streptomycetaceae.

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A technique is described for obtaining most probable number estimates of the number of cells of a bacterial strain(s) when it is present in low numbers in the soil. The technique is based on the bacteriophage response that is elicited when a known number of bacteriophage for the bacterium of interest is incubated with soil dilutions in a nutrient broth. The technique was evaluated for use with gram-negative bacteria.