Number and activity of active ribosomes in bacterial polyribosomes

Polyribosomes were isolated from Baccillus licheniformis, grown at 37 and 46 degrees C, and from Bacillus stearothermophilus, grown at 46 and 55 degrees C. The polyribosomes were incubated with either [3H]puromycin or [14C]phenylalanine. The number of active ribosomes (i.e. those to which growing polypeptide chains are attached) was calculated from the amount of [3H]peptidyl-puromycin formed. The activity of an active ribosome (i.e. the total number of amino acid molecules incorporated/unit time per active ribosome) was calculated from the uptake of [14C]phenylalanine. The number of active ribosomes per migrogram of RNA was as follows: for B. licheniformis, 1.66 X 10(12) and 1.72 X 10(12) at 37 and 46 degrees C respectively; for B. stearothermophilus, 2.59 X 10(12) at 46 and 55 degreesC respectively. The activity per active ribosome was as follows: for B. licheniformis, 0.61 and 0.05 at 37 and 46 degrees C respectively; for B. stearothermophilus, 0.58 and 0.42 at 46 and 55 degrees C respectively.