Bacterial Staining: After participating in this topic, students will be able to perform simple stains and several differential staining techniques that are used to observe unique molecules and structures found in various bacterial genera. The Gram stain, which aids in differentiating bacterial cell wall structure, the acid-fast stain, which detects mycobacteria, and the endospore stain, which detects endospore-forming bacteria, are useful for identification of these unique microorganisms. (Online) Manipulation of Microorganisms – Methods of Culture Transfer, Pure Culture Isolation, and Antimicrobial Testing: After participating in this lab, students will be able to use aseptic technique to transfer bacteria from one medium to another, use the streak-plate method to isolate bacterial colonies, and use the Kirby-Bauer disk diffusion assay to test for bacterial sensitivity to antibiotics, antiseptics, and disinfectants. The results of antimicrobial testing can help determine if a bacterial isolate is susceptible or resistant to various antibiotics, and may help direct a clinician to an effective treatment.
Objectives:
- Describe the rationale for the steps required to prepare a bacterial smear.
- Compare and contrast the staining characteristics of three species of bacteria using positive and negative staining techniques.
- Name four positive stains and two negative stains, and explain how their chemical charge affects staining of bacteria.
- Describe the morphology and cellular arrangement of two species of bacteria.
- Describe the steps of a Gram stain, and illustrate the type of cell wall structure present in Gram-negative and Gram-positive bacterial cell walls.
- Identify two acid-fast positive and two acid-fast negative bacteria, and describe the method and steps used in an acid-fast stain.
- Explain why the unique molecule found in the cell wall of an acid-fast positive bacterium causes this bacterial genus to be difficult to stain.
- Describe the method and steps of an endospore stain, and illustrate the staining characteristics of endospores and vegetative cells.
- Identify three bacterial species that form endospores and describe the disease caused by each one.
- Identify the distinguishing chemical found in the coat of endospores and explain its significance in the resistance of endospores to various chemicals/treatments.
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Bio-205L Microbiology Lab – Topic 3 DQ 1
Assessment Description:
Search through news articles or reports (within the past 5 years) on hospital infections that were caused due to a lack of aseptic technique. What happened to cause the spread of the pathogen? How could it have been prevented? Include references to your news article.
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Topic 4
Bio-205L Microbiology Lab – Topic 4: Bacterial Genetics and Midterm Exam
Some bacterial species have been found to take in DNA from the environment, and the newly acquired DNA may give them a selective advantage. Scientists can take advantage of this phenomenon by purposely transforming bacteria or inducing them to take up DNA. This method is used to study gene function and gene expression in bacteria and can have clinical relevance when bacteria take up an antibiotic resistance gene. Clinicians routinely take samples from patients, and if a microorganism is present in a patient sample, its genome is also present. To detect and identify the microorganism, scientists can assay for the presence of an organism’s DNA using a powerful molecular biology and diagnostic technique known as the polymerase chain reaction (PCR). The PCR products can be analyzed using agarose DNA gel electrophoresis. Students will complete the midterm exam at the end of this topic.
Objectives:
- Describe the method of bacterial transformation with plasmid DNA.
- List the DNA sequences/genes present on the pGLO plasmid and explain the function of each.
- Illustrate and interpret the phenotypic traits of transformed bacteria observed on non-selective and selective media.
- List the components needed to set up a polymerase chain reaction (PCR) reaction.
- Describe the three steps in a PCR cycle illustrating what happens in each step using DNA, primers, and Taq DNA polymerase.
- Explain how PCR cycles create copies of target DNA.
- Explain the theory of agarose DNA gel electrophoresis, analyze a PCR reaction using agarose DNA gel electrophoresis, and illustrate and describe the results.
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