A nutritional and taxonomic survey of Arthrobacter soil isolates

One hundred and sixty Arthrobacter soil isolates, four groups of 40 from each of four soil types, and 17 Arthrobacter named strains were characterized on the basis of 203 different nutritional tests performed on each culture. One hundred and twenty-one compounds were examined as sole sources of carbon, 44 compounds as sole sources of nitrogen, 22 carbohydrates for the production of acid, and 16 tests were done for tolerance to various dyes. The four groups of soil arthrobacters differed markedly in acid production from carbohydrates, and in utilization of aliphatic amino acids and aromatic hydrocarbons as sole sources of carbon. The named strains did not exhibit as much nutritional diversity as any of the four groups of soil isolates. The results of the nutritional tests were subjected to a computerized taxonomic analysis. Eighty-four of the isolates were contained in nine separate clusters with 87 to 94% similarity; 39 isolates were contained in five mixed but recognizable clusters with 84 to 86% similarity; 60 isolates were randomly mixed with no recognizable clusters and similarity of 72 to 83%. All clusters were composed of nearly equal numbers of isolates from each of the four soils; the named strains were not found associated with any of the clusters of soil isolates. The results indicated that the diversity of the genus Arthrobacter is not represented by the named species already described, and the possibility of using a series of standardized tests to categorize soil arthrobacters into readily identifiable nutritional groups is discussed.