The antibiotic penicillin kills bacteria by making them lyse (burst). It is more effective for diseases caused by Gram-positive bacteria than for diseases caused by Gram-negative bacteria. Outline how penicillin acts on bacteria and use Fig. 3.1 to suggest why penicillin has little or no effect on diseases caused by Gram-negative bacteria, such as some strains of E. coli.
Explain what the term passive means.
Suggest and explain the features that make an OmpF porin a membrane transport protein.
$\textit{E. coli}$ can control the number of OmpF porins in the outer membrane to adapt to changing conditions. One control mechanism used by $\textit{E. coli}$ is the production of a small mRNA molecule called micF. micF binds to the section of the mRNA molecule containing the START codon for the OmpF polypeptide. Suggest and explain how the presence of micF prevents production of OmpF porins.
Define \textit{polysaccharide}.
Some strains of $\textit{E. coli}$ are pathogenic. Different pathogenic strains have different O antigens. Suggest and explain why infection with one pathogenic strain of $\textit{E. coli}$ does not provide immunity to a different pathogenic strain.