POLARIZED-LIGHT SCATTERING FOR RAPID OBSERVATION OF BACTERIAL SIZE CHANGES

The effect of changing growth conditions on the diameter of rod-shaped bacteria was studied in vivo with the use of polarized light scatteri ng. The value of a ratio of scattering matrix elements was measured as a function of scattering angle at various times after nutritional ''u pshift'' for two strains of Escherichia coli cells, The peak locations of the scattering function were calibrated against the diameter for r od-shaped bacteria. The peaks moved toward smaller angles as a functio n of time after upshift, indicating that the diameter was increasing. Under special conditions, substantial peak shifts occurred within a fe w minutes of growth condition change, indicating a rapid onset of grow th in diameter. The rate of increase of the diameters after upshift wa s obtained from the angular shift of peak location, This rate was simi lar to 14 nm/min for E. coli K12 and similar to 9 nm/min for E. coli B /r at 37 degrees C. The rate of diameter increase is smaller at lower temperatures. Experiments with Bacillus megaterium showed that any dia meter change after nutritional upshift at 37 degrees C is limited to a t most a very small increase, at least for the strain and medium teste d.