Lab Practical 1
Study Guide & Overview
Your lab practical #1 will be on May 12 (M) or May 13 (T). Please try to coordinate in advance to ensure you arrive on time that day!
You may bring the following to the lab midterm:
- Any lab notes
- you may bring your notes on post-lab questions but please do not bring the questions & answers printed/handwritten
- Your lab notebook with:
- completed Staining Summary Table
- completed Pathogenic Cocci Media Table
- completed Pathogenic Cocci Results Table
Post-lab questions
Your post-lab questions are a great resource to review the major concepts from each lab. They will also give you a sense of the questions you might be asked.
Structure
Part 1 (Group): ID a pathogen
- 9-10:30am
- In the group portion, you will be given a short scenario of a patient who is ill. Based on the skills you've learned in the lab, you will identify the pathogen that is causing the patient's illness based on your interpretation of data.
- You will look at: colony characteristics, aerotolerance, shape/arrangement, gram status, and pathogenic media tests
- Please note that you will be given bacteria named cryptic things that don't exist in real life. In other words, you are being assessed on your skills rather than memorizing the traits of the bacteria we have seen so far. (In other words, I don't want you spending your time memorizing what Staph. aureus looks like, its aerotolerance, etc.).
- Dr. Y is around to help guide your group! My goal is for everyone to reach full credit here so I will be popping in and out to check on your progress and give feedback.
- If your group finishes early, you may move on to Part 2.
Part 2 (Individual)
- 10:30-10:45 streak plates
- Streak a culture for isolation using the techniques we learned in class. You will be assessed on isolation and sterility.
- If you do not achieve isolation, you may come in during office hours as many times as needed to receive the points on this (so please don't stress yourselves out here)
- 10:45-end of lab
- you won't need this whole time period, but I wanted to give LOTS of time so you can take as much time as you'd like
- Some MC questions (just a couple of these based on post-lab questions or your group case study in part 1)
- Some short response (3 as described below)
- you will be asked to design an experiment given an experimental question (be able to come up with the independent, dependent, and standardized/controlled variables)
- you will be asked to draw or interpret "mock" data based on labs we've previously done (e.g. aerotolerance or endospore for example)
- you will be asked to do calculations as we've done in lab (you can bring a calculator or I have some extras in lab)
From each lab, please be familiar with the following ideas (you may use this as a Study Guide):
While your post-lab questions should be the best way to review, some of you may feel more comfortable reviewing a set of specific questions so I compiled the topics/questions we've learned so far below.
Please be strategic about how you study. It is not a good use of your time writing & answering about concepts you already know. Rather, look at the questions below and focus on the ones you aren't sure about or don't remember at all! These are the places you need to spend your time on.
Note that everything is fair game but I did ** the things that will come up for sure!
Epidemiology will be covered in Practical 2
Introduction to Microbiology Lab
- Culture medium
- What conditions, molecules, and nutrients do microbes need to grow?
- Define and be able to identify the dependent, independent, and standardized variables in an experiment.**
Aseptic Technique & Culture Characteristics
- What is aseptic technique & why do we use it?
- How do we transfer bacteria from one culture to another without contaminating either culture? (Be able to describe the process)
- Draw/demonstrate the streak pattern on a plate that you would use to achieve isolation. Where/when should you be flaming your inoculating loop? **
- Define “colony” as it is used to describe growth on an agar plate in the lab (or be comfortable recognizing a colony & characterizing it)
- Identify characteristics you would use to distinguish two types of microbes growing on a dish. (note: you DO NOT need to know the fancy microbiology terms like lobate, etc.) **
Introduction to Microscopy
- Review care & guidelines for microscopes
- What should you do after finishing with the microscope?
- How should you handle/move the microscope?
- Can you find a specimen at 4X and focus all the way up to 40X or 100x oil? (you may be asked to do this in the group portion)
- Know how to calculate total magnification **
- Know how to estimate the size of a specimen on the microscope **
Introduction to Staining & Bacterial Cell Morphology
- Differentiate between a simple & negative stain
- How are the stains different?
- How are the staining protocols different?
- What do bacteria stained with a negative stain look like?
- What about bacteria stained with simple stain?
- Be able to ID, differentiate, and/or draw bacteria with different shapes (e.g. cocci, bacilli, spirilla) and arrangements (e.g. diplo, tetrad, strepto, staphlo. Here knowing the terminology is required) **
- Describe how to make a bacterial smear
- What is the purpose of heat-fixing cells?
Introduction to differential stains & cell wall characteristics
- What is the difference between a gram-positive and gram negative cell wall?
- What about an acid-fast cell wall?
- How can differential staining be used to ID an unknown bacteria?
- What is the protocol for the gram stain? What is the purpose behind each step? **
- what's the differential step? what does iodine do? what's the difference between CV and safranin?
- Be able to differentiate between gram-positive and gram-negative cells in an image or sample **
- What is the protocol for the acid-fast stain? What is the purpose behind each step?
- Can you predict how cells will look if a mistake is made in the staining procedures of gram or acid-fast stains? **
- hint, you did this for gram stains in your lab report
Differential Stains/Structural Stains
- What is a capsule? How do capsules help bacteria?
- Be able to identify a capsule-stained sample and the cell/capsule components stained or unstained.
- Describe the process of sporulation and germination. How do endospores help bacteria? When do bacteria make endospores?
- Describe the endospore staining protocol and be ready to ID endospores from a stained sample or image.
- What are flagella? How do they help bacteria?
Bacterial Aerotolerance
- How can thioglycolate media be used to determine the aerotolerance of bacteria?
- What are superoxide dismutase & catalase? What classes of bacteria make these enzymes?
- Distinguish between the anaerobic jar, the candle jar, and the aerobic environment we grow samples in **
- Can you tell me what environment each aerotolerance class will grow well in?**
- Can you interpret data to determine the aerotolerance class of a microbe?**
Pathogenic Cocci
- What are common characteristic(s) of the pathogenic cocci? (think about morphology, gram status, etc.)
- Can you describe what the following tests are used for? Are they selective and/or differential? What does a positive or negative result look like & can you interpret data? *
- Can you describe how forgetting an ingredient or changing pH would alter selective or differential tests below? *
- PEA
- MSA
- BEA
- Blood agar
- Catalase
- What is TSA used for when comparing results with some of the media above?
Absolutely! Let’s break down the diagram and the concept of DNA replication at the replication fork, especially focusing on why D ➔ B is the leading strand.
