Lab Quiz #3 – Flashcards
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| Chemically Defined Media |
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| Exact composition ratio of media is known -inorganic broths- lacks good carbon source -glucose salts broth- glucose as only carbon source |
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| Complex Media |
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| Made from plant or animal tissue extract- exact amounts are unknown- good source of organic compounds (sugar, AA's vitamins, minerals) -nutrient broth -yeast extract broth |
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| What does a spectrophotometer check? |
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| Turbidity- cloudiness- amount of bacterial growth |
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| Disadvantages of Spectrophotometer |
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| Doesn't differentiate between living and dead cells. Requires incubation, prone to human error (pipetting) |
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| advantages of Spectrophotometer |
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| instant reading, more quantitative measurement than using your naked eye to approximate cloudiness. |
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| Heterotroph |
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| Carbon source is from organic molecules |
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| Autotrophs |
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| Carbon source is from inorganic molecules- CO2 |
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| Chemotroph |
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| energy is obtained from chemical reactions (redox)- inorganic and organic chemicals |
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| phototroph |
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| energy is obtained from light |
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| For carbohydrate fermentation, what media and pH indicator were used to identify fermentation? |
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| media was nutrient broth with phenol red |
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| what were the three sugars used to measure carbohydrate fermentation? |
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| lactose, glucose, sucrose |
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| Which bacteria showed acid production with no gas formation? (yellow) |
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| S mitis and S aureus |
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| Which bacteria had acid and gas productions (yellow with bubble)? |
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| E. coli |
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| Which bacteria had no fermentation (no acid or gas)? |
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| A. faecalis and Pseudomonas |
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| Selective Media |
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| selects among a specific groups of bacteria- usually share common trait (gram positive, gram negative, halophiles) |
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| 3 types of selective Media |
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| -Crystal Violet Agar -Phenylethyl Alcohol Agar -7.5% Sodium Chloride Agar |
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| Phenylethyl Alcohol Agar (what does it inhibit, what does it select for) |
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| Inhibits Gram negative (alcohol disrupts membrane) Selects for Gram Positive cocci |
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| Crystal Violet Agar (what does it inhibit, what does it select for) |
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| Inhibits Gram Positive Selects for Gram Negative |
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| 7.5% Sodium Chloride Agar (what does it inhibit, what class of bacteria does it select for, give an example of a bacteria in this class) |
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| inhibits anything non-halophilic Selects for halophiles Ex: Staphylococcus |
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| Differential Media |
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| Selects specific organism within a group of bacteria (identifies species) |
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| 3 types of Differential Media |
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| -Mannitol Salt Agar -MacConkey Agar -Eosin-Methylene Blue Agar |
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| Mannitol Salt Agar (What group does it select for, what does it differentiate and how, provide examples) |
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| salt selects for halophiles- Staphylococcus Mannitol fermentation (pathogenic trait) differentiates epidermidis from aureus Ex: S. aureus ferments mannitol and turns red media yellow |
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| MacConkey Agar (What group does it select for, what does it differentiate and how, provide examples) |
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| Selects for gram negative (crystal violet inhibits gram positive) Differentiates lactose fermenting bacteria (coliforms) Lactose fermentation produces acids which turn the pH indicator red Ex: E. coli, citrobacter, Enterobacter, Klebsiella |
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| Eosin-Methylene Blue Agar (What group does it select for, what does it differentiate and how, provide examples) |
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| Selects for gram negative lactose fermenters (coliforms) Differentiates between E. coli and all other coliforms- E. coli produces metallic green color -Enterobacter aerogenes (coliforms)- pink colonies w central dark purple spot |
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| Enriched Media- example? |
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| Contain nutrients to support a wide variety of bacterial growth as well as additional unique requirements of fastidious growers Ex: blood agar |
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| Blood Agar (what does it differentiate? what are the three types of growth?) |
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| Differentiates hemolytic Streptococcus species (enriched and differential media) 1. Alpha hemolysis 2. Beta hemolysis 3. Gamma hemolysis |
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| Alpha hemolysis (what does it look like and what organism shows this type of growth?) |
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| Partial breakdown of hemoglobin shows green/light brown sheen around colonies (biliverden) Ex. E. coli |
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| Betta hemolysis (what does it look like and what organism shows this type of growth?) |
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| Full breakdown of red blood cells leaves clear space- lyse cells using beta-hemolysin (streptolycin) Ex: S. pyogenes |
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| Gamma hemolysis (what does it look like and what organism shows this type of growth?) |
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| no hemolysis- whitish grey sheen on surface of media Ex: S. epidermidis |
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| Enteric Bacteria (2 types) |
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| Bacteria that colonize the intestinal tract- coliform and non-coliform -ferment glucose -facultative anaerobes -usually gram negative bacilli |
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| Coliforms |
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| lactose fermenting enterics Ex: E. coli, citrobacter, Enterobacter, Klebsiella |
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| Non-Coliforms |
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| non-lactose fermenting enterics Ex: Salmonella, Shigella, serretia, proteus |
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| [image] |
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| mannitol salt agar |
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| [image] |
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| Alpha Hemolysis (Blood Agar) |
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| [image] |
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| Betta Hemolysis (Blood Agar) |
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| [image] |
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| Gamma Hemolysis (Blood Agar) |
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| [image] |
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| MacConkey Agar |
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| [image] |
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| Eosin Methylene Blue Agar (E. coli) |
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| [image] |
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| Eosin Methylene Blue Agar (Enterobacter Aerogenes) |
