<p>Microbial Diversity MIC/PLP329 Final Exam Fall 2002 Answer three of the six following questions (about one page per question; open book, no discussion among students). In addition to the class handouts and syllabus links, do some web/medline searching on your own. Answers are due on Thursday December 13 by 5pm.</p><p>1. Discuss mechanisms of spore resistance in Bacillus subtilis (see syllabus and links to Dr. Nicholson’s lecture).</p><p>2. Discuss the variety of roles that fungi play in our daily lives. Include the importance of both pathogens and saprobes. (Dr. Orbach’s links from syllabus web page)</p><p>3. Discuss mechanisms by which species of Cryptospiridium invade and are pathogenic to animal host cells. Why might host animals die? (Dr. Riggs)</p><p>4. Explain why RNA viruses are often denoted "quasipecies". How does this concept relate to the emergence of antiviral drug resistance in HIV? (See Dr. Collins handout papers)</p><p>5. Provide several lines of evidence that argue for co-evolution between whitefly- transmitted viruses and their vector, Bemisia tabaci, which have led to strict virus-vector specificity. (If you chose this question, send Dr. Brown an email and she will send you the required references)</p><p>6. The Microviridae have evolved to be small. In the last few years a subfamily of the Microviridae, whose members infect obligate intracellular bacteria like Chlamydia, has been defined. The members of this subfamily, the Chp-like viruses, are significantly smaller than the ΦX174-like subfamily. ΦMH2K is a member of this subfamily. One of the major differences between the two subfamilies is the absence of genes in the Chp-like viruses that encode the external scaffolding and five-fold related spike proteins (see figure). The Chp-like viruses also have coat proteins which form large protrusions at the three-fold axes of symmetry (see figure). In addition, the internal scaffolding protein may have evolved into a structural protein. Some functions of the ΦX174 internal and external scaffolding proteins are summarized below. </p><p>Functions of the ΦX174 external scaffolding protein. A. Stabilizes three-fold axes of symmetry in the procapsid. B. Stabilizes the two-fold axes of symmetry in the procapsid. C. Placement of the five-fold related spike protein.</p><p>Functions of the ΦX174 internal scaffolding protein. A. Prevents premature association and aggregation of coat protein. B. Stabilizes the two-fold axis of symmetry in the procapsid.</p><p>A. Based on the information given in this question, hypothesize why the Chp-like viruses have loss their external scaffolding proteins and why their internal scaffolding proteins have evolved into structural proteins. (see Reading 2 of Dr. Fane’s lecture: Liu et al. Virol. 2000 Apr;74(8):3464-9).</p><p>B. The authors hypothesize that Vp3 is equivalent to the ΦX174 internal scaffolding protein. Of the data they present, which are the most convincing and why?</p>