Effect of freezing and thawing on survival of three bacterial isolates from an arctic soil.

Three isolates, a Pseudomonas sp., Bacillus sp., and Arthrobacter sp., which had been isolated from a meadow soil at Devon Island, Canada, were subjected to freezing and thawing at low rates under various conditions. When cells were frozen in sand or soil, survival was dependent on moisture level, storage time, and thaw rate. Pseudomonas M216 was most susceptible to freeze-thaw damage under these conditions. Arthrobacter M51 was the most resistant of the three isolates when frozen in sand or soil and when frozen at a high rate after growth at varing rates at 5 and 15 degrees C in carbon-or nitrogen-limited media. Pseudomonas M216 was more sensitive to freeze-thaw damage when NaCl was present in the freezing menstruum, even at low freezing rates. Survival of cells frozen in growth medium, water, saline, and soil extract was not affected by the freezing rate when it was less than 1 degrees C min-1. Soil extract did not protect cells from freeze-thaw damage any more than water and for Arthrobacter M51 survival was decreased when it was frozen in soil extract.