FIG. 2.

Phenotypic characterization of htrA mutant strain. (A) Overnight cultures of the wild type (NG-8) and its isogenic htrA mutant strain (IBS101) were grown in THY medium and the bacteria were visualized by scanning electron microscopy (magnification, ×1,600). (B) Effect of temperature on the growth of S. mutans strains. Different dilutions of fresh overnight cultures were spotted on MS-agar plates and incubated under microaerophilic conditions at the indicated temperature for 40 h before photographed. Samples are NG-8 (wild type), IBS101 (htrA), and IBS101/pIB108 (htrA/htrA⁺). Experiments were repeated no fewer than three times and relevant areas of representative plates are shown.