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Micro Lab 6
| Question | Answer |
|---|---|
| Purpose of Selection of Fungi From Air Experiment | To favor (or select for) the growth of organisms over other organisms that might be present. |
| Mycophil | The selective media that we will be using is Mycophil. This medium is selective by pH, it has a pH of ~5. |
| TSA (tryptic soy agar) | We will also use TSA (tryptic soy agar), a general-purpose, non-selective medium that will allow growth of many different organisms. The pH TSA is ~7. |
| Section of Fungi Experiment Summary | You will use the pour plate method to make petri plates with TSA and Mycophil, then expose the plates to the outdoor environment for five minutes. The growth that will occur with either be bacteria or fungi; fungi grows due at a more acidic pH. |
| Primarily two properties of agar make it a more suitable gelling agent for most microbiological purposes than gelatin. | Most microorganisms can't utilize the polysaccharide in agar as a carbon source. If they could, it would degrade the solid medium. Second, the physical properties of the agar polymer make it very handy to work with. |
| Agar Temperatures | Medium is liquid until it cools to ~42°C. This allows you to pour it into whichever format you desire. Once agar solidifies, remains solid until heated to 100°C. You can incubate cultures at elevated temperatures and the culture medium will remain solid. |
| Selection of Fungi From Air Experiment Predictions | start with the assumption that the colonies that are round, shiny and smooth are bacterial and the filamentous (fuzzy) colonies are fungal. |
| Hypothesis: | If pour plates of TSA and Mycophil are exposed to an outdoor environment, more fungal growth will be detected in the Mycophil plate as a result of its pH level. |
| Ubiquity: | everything is everywhere, all at once |
| Selection: | select for growth, inhibiting other organisms from growing. Allow the growth of some organisms (those that can grow at ph 5), while inhibiting the growth of others. |
| Why are metabolic tests important? | The observed differences in the metabolic capabilites of organisms are a reflection of genetic differences. |
| Inherently visible reaction product | Can be directly observed without any addition of indicators or chemicals. Example: Catalase test = reaction product is bubbles |
| Inclusion of an appropriate pH indicator | Observation of a color change in the medium; observation of either an acidic or alkaline byproduct Example: Phenol Red Lactose or Glucose broths, citrate slant, urease test |
| Addition of a chemical compound after the organism has been grown | A direct observation of inclusion of a pH indicator is not possible, so a chemical compound will be added to the reaction that will modify the product or form colored compound. Example: Oxidase test |
| Introduction | The hypothesis must be clearly stated in the Introduction If there is unattributed copying from the Lab Manual – 0 pts for the introduction For full points, there needs to be background material from another source and it needs to be referenced. |
| Materials and Methods | Cite the lab manual, and add anything that is not included. Note any deviations from the lab protocol. |
| Results | This section should include criteria and evaluation of the criteria Criteria Tables (personal, section, class data) Pictures (properly labeled, tables too. Descriptive text |
| Discussion | readdress the hypothesis – discuss the results as they stand and also in the context of known scientific literature. |
| Conclusion | state whether YOUR hypothesis was supported or not (based on the entire class data) |
| References | References will be cited according to the ASM style instructions found on Canvas |
| Purpose of Enzymatic Activity Unknown | to determine whether the control and unknown specimens produced cytochrome c oxidases |
| Enzymatic Activity Unknown Specimens | The specimens in question were the following: Pseudomonas flourescens (positive control), Escheroli coli (negative control), and an unknown specimen. |
| Catalase test | Detects the presence of the enzyme catalase, which breaks down hydrogen peroxide (H₂O₂) into water and oxygen—bubbles indicate a positive result. |
| Oxidase test | Identifies bacteria that produce cytochrome c oxidase, an enzyme in the electron transport chain— a color change to dark purple indicates a positive result. You have to add a drop of a solution of tetra-methyl-etc and color change means oxidation by air. |
| Catalase controls | micricoccus luteus (POs), streptococcus thermophilis (neg) |
| Oxidase controls | pseudomonas fluorescens (POs), escheroli coli (neg) |
| You need 400 mL of nutrient broth at 8 g/L. How many grams of powder do you weigh out? | 8g/L×0.400L=3.2g |
| How many grams of agar are needed to make 750 mL of 1.2% agar solution? | 1.2% means 1.2 g per 100 mL of solution. So 1.2/100 = x/750, cross multiply 1.2*750/100 = 9.0 g. |
| You add 2 mL of a 10 M NaCl stock into 98 mL of water. What is the final concentration? | Use M1,V1 = M2,V2 equation (2)(10) = (x)(98+2) (2*10)/100 = 0.2 M |
| If you want 250 mL of 0.5 M glucose from a 2 M stock, how much stock and water do you use? | ((0.5)(250)) / (2) = 62.5 mL stock. Add 187.5 mL water. |
| Why do we identify microorganisms? | To identify infecting microorganisms for proper treatment. Infer functions of the identified organisms in the environment. |
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smurtab