Environmental Microbiology Flashcards
What Is Environmental Microbiology?
Studying Composition + Physiology of Microbial Communities
Examples:
- Soil, Water, Sediments
- Humans/Other Animals
- Artificial Environments
What Did John Snow Do?
- Disproved Miasma Theory
- Showed linkage Between Contaminated
Water and Cholera
Describe Vibrio Cholerae.
✓ Gram-
✓ Curved Rod
✓ Highly Motile
✓ Non-Spore Forming
✓ Oxidase positive (It produces Cytochrome C)
✓ Pili
Causes/Symptoms:
- Diarrhea
- Dehydration
- Vomiting
How Does a person become Infected with Cholera?
What does Cholera Do?
Infection: Contaminated Food/Water
Effect:
- Colonizes Epithelium Of Small Intestine
- Secretes enterotoxin
- Ion Transport Disrupted
- Water + Electrolytes Lost
Consequence: Diarrhea
How Is Cholera Diagnosed In A Laboratory?
Terms
Alkaline Peptone Water (APW)
Enriched Dipstick Test
- Faecal Sample needed in a cup
- Cotton Swab used to inoculate APW Tube
from faecal sample - After 6hrs of Incubation, APW Is Tested with
Crystal VC (Test for Cholera Antigen) - If Dipstick is Positive = Confirm sample with
TCBs - (Optional) Add 2 drops onto Protein Saver
Card, allow to Dry to save DNA from APW for
confirmation using PCR
What is TCBS? What Is The Purpose for Each Component?
Thiosulphate Citrate Bile-Salt Sucrose Agar
Thiosulphate + Sodium Citrate:
- Alkalinity of Media
- inhibit Enterobacteria Growth
Ox Bile + Sodium Cholate:
- Slow Enterococci Growth
- Inhibit Gram+
Bromothymol Blue + Thymol Blue:
- pH Indicators
Thiosulphate:
- Sulphur Source
Yeast Extract + Peptone:
- Growth
Sodium Chloride:
- Optimum for Halophilic Vibrio sp.
Agar:
- Solidifying Agent
What Are The Requirements For An Indicator Organism?
- Must Be Present when pathogen is Present
- Must Be Absent when Pathogen is Absent
- Conc must Correlate with Pathogen Conc,
but Indicator Conc should Always be Higher - Indicator should Survive Easier + Longer
than Pathogen in environment - Indicator Detection should be Easy, Safe +
Inexpensive - Indicator Must be Effective On All Water
Types
Describe Coliforms
Gram Negative Rod Shaped Bacteria that Act as Indicator Organisms. They Primarily Ferment Lactose.
They:
- Are Non-Spore Forming
- Are Motile/Non-Motile
- Produce Acid + Gas at 37°C
What Are the 2 Types Of Coliforms?
Total: Found In Soil, Water , Plants (Not all
Harmful)
Fecal: Subgroup That Live In Intestines of
Warm Blooded Organisms
What Is Most Probable Number Analysis (MPN)?
Statistical Method To Estimate Bacteria Concentration In a sample
Used when Bacteria are Present In Low Numbers + Need To Be Counted indirectly
Example uses:
- Testing Drinking Water For Fecal
Contamination - Checking Food Safety
- Detecting Pathogens
How Is MPN Carried out?
- Reagent Added To Sample
- Sample Added into Quanti-Tray
- Quanti-Tray sealed with Quanti-Tray Sealer
- Sample incubated for 24hrs at 35°C
- Sample Read under UV light
- Blue Fluorescent Wells counted + Referral to
MPN Table
What Are The Advantages and Disadvantages of MPN?
Advantages:
- Works For Low Bacterial Numbers
- Detects Live Bacteria
Disadvantages:
- Takes 24 hours (slower than PCR)
- Less precise than direct plating
What is The Catalase Test?
Bacterial Isolate is added to Hydrogen Peroxide
Catalase-Positive Bacteria Produce Oxygen Bubbles
What is The Oxidase Test?
Test that Identifies Bacteria that Produce Cytochrome C Oxidase (Enzyme from Bac ETC)
What are the 3 Steps of Drinking Water Treatment?
- Coagulation
- Filtration
- Chlorination
What Happens In Coagulation and Flocculation?
- iron/Aluminum Salts/+tive Charge added
- Binding to suspended particles
- Suspended Particles Neutralized
- Large Particles Settle (Sedimentation)
** Not All Viruses/Bacteria Are Removed **
What Happens In The Filtration Stage?
Water Forced Through Porous Media with
Varying Pore Sizes
Media: Made of Sand, Gravel + Charcoal
Slow Sand Filtration:
Removes bacteria, Protozoa + Viruses
Rapid Sand Filtration:
Removes Suspended particles
No Bacteria, Protozoa or Viruses Removed
What Happens In The Chlorination Stage?
Chemical Disinfection
Bacteria Inactivated By:
- Damaging Cell Membrane
- Disrupting Respiration
- DNA Activity Disrupted
What Are Compact Dry Plates?
A plate used for counting micro-organisms
- Sample Added to Plate diffuses evenly
Throughout media - Once grown, Colonies are Pigmented with
Different Colours
What is a RIDA®CHECK?
A Diagnostic Test to Detect harmful Substances in Food, Water + Clinical Samples
✓ Protein residues – independent of ATP
✓ React with indicator molecule
✓ Colour change from Yellow to Green
✓ Colour Intensity indicates level of
Contamination
What Is LuciPac PEN?
✓ Rapid detection of food and microbial
residues
✓ Detection of ATP and AMP
✓ Portable Luciferase assay
✓ Machine reads light intensity
