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Abstract
SUMMARY: When Arthrobacter globiformis, A. simplex, A. crystallopoietes and A. atrocyaneus were grown in a chemostat, their morphology was related to growth rate. A transition from rod to coccus occurred at growth rates characteristic for each species; the higher the rate at which this transition occurred, the higher was the maximum specific growth rate. Organism size, concentration and viability were determined for A. globiformis at a range of dilution rates between 0·01 h−1 and washout. Yield remained constant except at low dilution rates, although the number of organisms varied because of the changes in their size and shape. The percentage of viable organisms in the chemostat remained almost constant at dilution rates above 0·1 h−1 (92 %) and was only slightly lowered even at dilution rates as low as 0·01 h−1.
Rods grown in the chemostat and then placed in nutrient-free solutions divided and produced cocci which survived for about 56 days. Cocci survived for about 70 days. The respiration rate of freshly harvested rods was higher than that of cocci but within two days both fell to low levels.
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