An Ecological Study of the Psychrotrophic Bacteria of Soil, Water, Grass and Hay

Summary. A study of the psychrotrophic bacterial content, determined at 3–5°, of soil, grass and hay showed that these habitats were prolific sources of many different types of psychrotrophs, which sometimes exceeded 10 7 /g. Untreated farm water supplies had a much lower content, few samples giving colony counts > 10 4 /ml. Gram positive or Gram variable, nonsporeforming rods, resembling coryneform bacteria, constituted a relatively high proportion of the psychrotrophic microflora of soil, Gram negative rods only forming about 1/3 of the isolates. In contrast, Pseudomonas and Acinetobacter spp. and yellow or orange pigmented Gram negative rods were the predominant psychrotrophs in untreated water. Pseudomonas and a taxonomically heterogeneous group of yellow pigmented, Gram negative rods, a few of which resembled Flavobacterium and some Erwinia herbicola , together with Acinetobacter accounted for nearly 90% of the isolates from grass, but < 50% of those from hay, which had a more complex psychrotrophic microflora than had grass.