Question

6. What role have bacteriophages played in pathogen evolution?

7. Some researchers have tried to identify the PAIs in Salmonella by comparing the E. coli K-12 genome with that of S. enterica serovar Typhimurium. What are the advantages and disadvantages of this approach?

8. Which types of variation in surface antigens would still be seen in a strain of N. gonorrhoeae that was de- ficient in the ability to carry out homologous recom- bination?

9. Bacterial cells have the ability to change the set of genes that they express in response to changes in the environment. Explain why the ability to ‘‘turn on’’ only those genes that are needed at a given time is an advantage to the bacterium

. 10. Joe is a sexually promiscuous 22-year-old who has had gonorrhea five times in the past 2 years. Each time he went to the doctor, he was given antibiotics, and the infection cleared up. List at least two reasons why N. gonorrhoeae was able to cause recurrent infec- tions in Joe. Could Joe be vaccinated to avoid these recurring infections? Why or why not?

Answer 1

Answer 6.

Bacteriophages play an important role in microbial evolution which leads to emergence of new bacterial pathogens like salmonella. Lysogenic conversion by bacteriophages give an advantage to bacteria that bacteria do not require any contact to transfer plasmids as requires in conjugation process. Bacteriophage can survive under extreme conditions which are harmful for bacteria with carrying DNA of host. And this DNA material can be reintroduced to the host cells under favourable conditions. There are virulence factors which are encoded on bacteriophages which allows bacteria to increase their host range by counteracting host structural barriers. And also bacteriophages help in spreading DNA to all the population of specific bacteria without clonal expansion.

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