Compare and contrast bacteriocidal, bacteriostatic and bacteriolytic agents. What are their effects on the optical density (OD) and viable count of a bacterial culture, respectively?
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Compare and contrast bacteriocidal, bacteriostatic and bacteriolytic agents. What are their effects on the optical density (OD) and viable count of a bacterial culture, respectively?
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- The Kirby-Bauer test examines the effectiveness of antibiotics and disinfectants or antiseptics on separately plated bacteria. Which of the following Zones of Inhibition (ZOI) measurements on a plate of Klebsiella pneumoniae shows the strongest inhibition of the bacterium's growth? a) Penicillin, 7 mm ZOI b) Actinomycin, 9 mm ZOI c) Tetracycline, 26 mm ZOI d) Chloramphenicol 2 mm ZOI e) Streptomycin, 23 mm ZOIBased on the knowledge acquired about the conservation and propagation of microorganisms, propose methodologies for:a) conservation of stock culture (used infrequently) of baker's yeast (S. cerevisiae);b) conservation of the working culture (used daily) of the baker's yeast;c) activation (1st stage of propagation) of the work culture;d) propagation of cultures until inoculating a 100 L reactor toi) production of baker's yeast;ii) ethanol production.). Consider a culture medium on which only gram-positive organisms such as Staphylococcus aureus colonies can grow due to an elevated NaCl level. A yellow halo surrounds the growth, indicating the bacterium fermented sugar in the medium, decreasing the pH as a result and changing the color of a pH indicator chemical. This type of medium would be referred to as a(n): A) Selective medium. B) Differential medium. C) Enrichment culture. D) Selective and differential medium. E) Differential and enrichment culture.
- a) What is morphology? b) Describe the common morphological characteristics of bacteria that are often used in microbiological studies. c) Explain the chemical and physical requirements needed for bacterial growth d) Explain the importance of using growth medium and devise a STEP-BY-STEP plan to grow bacterial cell cultures in the laboratory.Mannitol salt agar is often used to distinguish between different species of Staphylococcus, a gram positive bacterium that is well adapted to living on dry, salty skin. Disease-causing strains of Staphylococcus ferment mannitol; non-pathogenic strains cannot use mannitol. Is the medium Defined or Complex?In a serial dilution, you plate 1 ml of a 1/1000 dilution of a bacterial culture and find 25 colonies the next day. What was the concentration of cells in the original culture? A) 25 cells/ml B) 0.000025 cells/ml C) 25,000 cells/ml D) 26 cells/ml E) 0.025 cells/ml
- You take 10 ml of a stock solution, which is at a concentration of 1000 phage/ml, and dilute it to a total of 100 ml. From the resulting solution you take 5 ml and dilute it to 25 ml, and from the latter you take 5 ml and make a total of 20 ml. a) It will be possible to know how many bacteriophage particles there will be in 1 ml of the last solution b) What is the dilution factor in each step, in the same order in which the dilutions are made? c) What is the total serial dilution factor?If a bacterial species is not susceptible to an antibacterial drug at the concentration present in a particular disk, does that necessarily mean the species is completely resistant to the drug? Explain your answer. What is the mode of action of bacitracin? How does this influence the types of bacteria it can be used against effectively? What is the mode of action of tetracycline? How does this influence the types of bacteria it can be used against effectively? Describe how populations of bacteria can evolve resistance to antibiotics. In your description, use the terms/phrases: mutation, resistant, sensitive, individuals, populations, natural selection, horizontal gene transfer.Draw a semi-logarithmic diagram showing the killing kinetics of a vegetative bacterial culture, assuming appropriate temperature, e.g. 100°C. Label the axes. 1.) What are the kinetics for killing bacterial spores at 100°C and 121°C 2.) and what about a mixture of different heat-resistant vegetative cells?
- You have used morphological observations and biochemical tests to identify two unknown bacterial isolates in your practical sessions, briefly describe three other techniques that can be used to identify unknown bacteria (you can use any reliable online resources). Note: These must not be based on biochemical tests (enzyme use, acid production etc) or morphological characteristics (size, shape, structures).Why is aseptic urine collection important when cultures are ordered? If you counted 20 colonies from a 0.01-ml inoculum of a 1:10 dilution of urine, how many organisms per milliliter of specimen would you report? Is this number significant? What can you learn from visual inspection of a urine specimen? How would you relate these to the microorganisms present in the sample? How are UTIs acquired/transmitted? Explain why E. coli is frequently implicated in cystitis in females.Which among A-D is false regarding growth and/or analysis of a bacterial culture? A) O Fed-batch growth: typically results in an increased yield of cells over that obtained with batch growth B) O Auxotroph: requires addition of specific growth factors in order to grow C) O Prototroph: typically the wild type strain that possesses all the features indicative of the species D) O None of A-D is false; all are true statements