Microbiology Exam Essay Example | Topics and Well Written Essays - 1250 words

Microbiology Exam - Essay Example Some viruses (animal viruses and bacteriophages) have the capsid encased in an envelope. In addition they are non-membraneous and cannot yield energy. They are also devoid of metabolic enzymes and ribosomes that form the sites for protein biosynthesis.Moreover, they need host cells to replicate. Viruses are transmitted via salivary drops, respiratory fluids, sexual contact, fecal-oral especially in case of contaminated food, animal vectors and via blood. Viroids- Comprise of single-stranded and circular RNA which is noncoding and infect plants. As compared to viruses their genome is much smaller, are protein non-coding, and unlike viruses some possess ribozyme activity. They initiate infection in plants via chloroplast or nuclear replication and they are conveyed in cells via plasmodesmata. Prions- Infectious agents that solely comprise of a protein whose form is misfolded. This is a distinguishing feature as they lack nucleic acids i.e. RNA/DNA. These potent agents means of propagat ion is via inducing folded proteins in healthy organisms to change (misfold) and assume the form of the prion; these have the ability to cause disease. The resultant stable structure causes cell death and tissue damage (Tortora, Funke & Case, 2010). 2. How can viruses lead to cancer? Be sure to use specific examples (e.g. virus name and the cancer it causes) to illustrate your points. Viral transformation mediated via viral genes results to uncontrolled cell growth with contact inhibition loss, tumor formation as well as chromosomal aberrations. In addition viral oncogenes that transform normal cells into malignant cells are transmitted by viruses. Viruses also inactivate the tumor suppressor proteins. The human papilloma virus (HPV) is the causative agent for cervical cancer and it integrates in the host’s genome and suppresses the expression E2 viral gene which represses the expression of viral oncoproteins E7 and E6. E6 has a high binding affinity for p53(tumor suppressor gene) and triggers its degradation and E7 binds to retinoblastoma(Rb). Rb and p53 are tumor suppressor proteins. This results to apoptosis inhibition and dysregulation of cell growth. E6 possesses the ability to trigger telomerase activity as well as immortalizing cells. E7 also triggers abnormal centriole biosynthesis as well as aneuploidy during the initial oncogenic process. Hence, E7 and E6 are synergistic in transforming normal cells to a state of malignancy. However, there is a genetic predisposition to the progression of cervical cancer. Moreover, acute immunosuppression heightens the propensity of cervical dysplasia and subsequent cancer progression (Damania, 2006). 3. You are growing Bacillus subtilis in nine 16,000-liter fermenters to produce enzymes for industrial use. The Bacillus cultures had been growing for 2 days when the cells in one of the fermenters lysed. Explain what happened in this fermenter. This is likely to be a case of bacteriophage contamination. Bacterio phages are a class of viruses that infect bacteria. Upon infecting bacterial cultures, they cause serious problems and this entails complete loss of bioproducts; in this respect enzymes and their subsequent proliferation in the plant (to other fermentors). This results to culture lysis and unless it is contained, the problem is bound to reoccur even after stringent sterilization of equipment. Decontamination is much difficult in such a large scale fermentor. It is has been proven that phage propagation in such a bioreactor can easily spread