Figure 4. Inactivation of phrB effects colony size and cell morphology.

A. Colony phenotypes. Shown are representative stereo micrographs of the parental, phrB mutant (PhrB−) and complement colonies grown at 37^°C in 5 % CO₂ for 22 hours. B. Colony diameters. Shown is the average colony diameter of the parental, phrB mutant (PhrB−), and complement strains. Error bars represent the standard error of the mean of 20 colonies. The diameter of the phrB mutant is less than the parental strain as measured by Student’s t-test, P<0.05 (asterisk). C. Growth quantification. The average colony forming units (CFU) per colony for 6 independent colonies of the parental, phrB mutant (PhrB−), and complement strains is shown after 22 hours of growth at 37^°C in 5 % CO₂. Error bars represent the standard error of the mean. D. Thin section transmission electron microscopy of cellular morphology. Representative micrographs of the parental strain and phrB mutant (PhrB−) are shown. The average cross-section diameter of 100 (79 monococci and 21 diplococci) parental strain cells was 0.86 +/− 0.01 μm while the average cross-section diameter of 100 (84 monococci and 16 diplococci) phrB mutant cells was 0.99 +/− 0.02 μm. Cell cross-section diameter was measured from two independent experiments. The average cross-section diameter of the parental strain is less than the phrB mutant as measured by Student’s t-test, P<0.05. Of the cells measured, 21 and 69 were not uniformly coccalcoccal for the parental strain and phrB mutant, respectively.