Streptococcus Pneumoniae Is a Gram-Positive Bacterium That Colonizes the Mucosal

Multiple Choice

Streptococcus pneumoniae is a Gram-positive bacterium that colonizes the mucosal surface of the upper respiratory tract in humans. The presence of this bacterium in the nose and throat is widespread in the population, and in most people, colonization with Strep. pneumoniae is asymptomatic. Figure shows a comparison of in vitro growth curves of the wild-type strain of Strep. pneumoniae, as well as a Strep. pneumoniae mutant strain with a defect in one bacterial gene. The graph on the right shows the growth curve following addition of lysozyme during the logarithmic phase of bacterial growth.
Which statement could account for the data in these graphs?

A) Strain B is wild-type Strep. pneumoniae, and strain A is a mutant that cannot modify its peptidoglycan to be lysozyme-resistant.
B) Strain B is wild-type Strep. pneumoniae, and strain A is a mutant that that expresses increased levels of LPS.
C) Strain A is wild-type Strep. pneumoniae, and strain B is a mutant that cannot modify its peptidoglycan to be lysozyme-resistant.
D) Strain A is wild-type Strep. pneumoniae, and strain B is a mutant that secretes an enzyme that inactivates lysozyme.
E) Strain A is wild-type Strep. pneumoniae, and strain B is a mutant that cannot grow well in vitro.