Microbial Growth Media and Bacterial Characteristics

Thymine Dimers

formed by dimers can destroy or distort DNA

Bacteria used in Lab 12 (UV radiation on bacterial growth)

-Deinococcus radiodurans: an extremophile that measures the effectiveness of ionizing radiation in food preservation. - -Ecoli

Coliform Bacteria

-Gram Negative

- Lactose Fermenting Bacilli (in the gastrointestinal tract of mammals)

Fecal Coliform

-Present in the gut and feces

-Indicates fecal contamination ( failure in water)

Selective Media

- Allows the growth of microorganisms while suppressing others

Differential Media

-Used to differentiate closely related microorganisms (based on colors and patterns)

Fastidious

-Species that require complex growth media for culture

Hemolytic

- Rbc incompletely erythrocytes and convert hemoglobin to methoglobin, called alpha and beta hemolysis

- Beta hemolysis is the destruction of red blood cells

Blood Agar (Apperance) Alpha and Beta

Appearence

- Alpha: Greenish grey or brownish discoloration

- Beta: Clear ( around the colonies)

-

Blood Agar ( What is it)

Identifies the organism (ie: hemolysis cau7sed by growing bacteria)

EMB Agar (Apperance)

Metallic Green= Lactose/ Sucrose

Brown/Pink= Slow fermenting Lactose

EMB Agar (Dye used)

Eosin and Methylene Blue

-The Dye is a differential indicator

-The dye inhibits the growth of many microorganism

EMB Agar (What is it)

- Lactose Fermenting

-Methylene Blue

-Gram Negative

-Selective and Differential

- Isolates Bacilli in foods

Mannitol Salt Agar (MSA) (Appearance)

Red AKA: "PHENOL RED", Stap E, Negative - Acid production

Yellow= "Coagulate"- Positive

Mannitol Salt Agar (MSA) (What is it)

-Used as selective and differential for the identification of Staphylococcus aureus and Staphylococcus epidermidis

- Only allows halophilic (salt-loving) and halotolerant ( salt-tolerant)

-supplies electrolytes

MacConkey Agar ( Appearance)

Red or Pink- Lactose Fermenting

Colorless- Non-Lactose fermenting

MacConkey Agar (What is it)

- Differentiation of Lactose Fermenting + Non-Lactose Fermenting

-Isolation of coliforms + intestinal pathogens in water and dairy

-Isolation of Gram-Negative Bacteria

Blood Agar: what are the two kinds of Agar

Alpha: Greenish-grey or Brownish

Beta: Clear

Names of the Agar done in class

Blood Agar

EMB

MacConkey Agar

Mannitol Salt Agar

Hemocytometer ( What is it for?)

-Used to make a direct count cells in a sample.

-Goes from small volume to Larger volume of 1 mL

Yeast cells are

fungus and unicellular

What is Methylene Blue used for?

Stains dead cells

Units for cell quantity

cells/cm3

or

cells/mL

and

1 cm3 = 1 mL

Turbidity

cloudiness of water

spectrophotometer

An instrument that measures the turbidity of a solution

and beam of light through a solution (measures absorbance)

Absorbance

Measures how much light is absorbed

Transmittance

Measures how much light passes through the solution

More Light goes through=

Higher Transmittance

ie: sterile water is high transmittance

because its clear and has no absorbance

More light blocked=

Higher Absorbance

ie: in a solution of yeast absorbance is high

Antibiotic Resistant Strains

Staphylococcus aureus

Neisseria gonorrhoeae

Mycobacterium tuberculosis

= infects the skin, genitourinary or respiratory tract and infections

Bacterial Lawn Steps

1) Label plate

2) Use antiseptic technique to obtain a bacterial sample from the liquid culture with sterile swab

3) Prepare a bacterial lawn on your Muller Hinton agar plate ( rotate the plate between streaks to cover the surface) Let it stand for 5 mins

4) Place four different antibiotic discs into the center of each quadrant

5) Incubate inverted plates for 18-24 hours at 35 Celsius

Disk Diffusion Test

Test how effective different antibiotics are against bacterial strain (like the antibiotic-resistant strains)

Direct Sandwich ELISA

Detects a specific antigen