MCB LAB Exam 4 Vocab

General purpose media

Media that has a wide variety of fuel supplies available & supports growth of most types of bacteria

Enriched media

Media that has been supplemented with highly nutritious materials

Selective media

Media that incorporates chemical substances that inhibit the growth of 1 type of bacteria while permitting the growth of another

Differential media

Media that incorporates chemical compounds that produce characteristic changes in appearance of bacterial colonies

Alpha hemolysis

• Shows a green / brown color in medium

• Partial hemolysis of RBCs

Beta hemolysis

• Area appears yellow / transparent

• Clear halo around colony

• Complete hemolysis of RBCs

Gamma hemolysis

• Does not break down RBCs

• Leaves RBCs intact

• Red color stays unchanged

• No color change on agar plate

Hemolysins

Toxins produced by bacteria to destroy RBCs

Streptolysins

Hemolysins produced by Streptococci

Inhibitor

Substance that prohibits growth of organisms (i.e. dyes, antibiotics, salts)

Indicators

• Color changes due to change in pH or presence of certain
  byproducts of the organism’s metabolism

• Used to identify bacteria

Staphylococcus Aureus

• Most pathogenic of Staphylococci

• Mannitol fermenter

Staphylococcus Epidermis

• Non-disease causing Staphylococci

• Grows but doesn’t change color of Mannitol Salt Agar

S. pyogens

• Bacteria that will cause beta-hemolysis on a blood plate

• Causes strep throat

S. pneumoniae

Bacteria that will cause alpha-hemolysis on a blood plate

E. faecalis

Bacteria that will cause gamma-hemolysis on a blood plate

Osmotic Pressure

Amount of force applied to a solution that prevents solvent from moving across a semipermeable membrane

Isotonic solution

• Solution that’s equal in solute concentration to the cell

• Water moves in & out of the cell at a similar rate

• Same osmotic pressure

Hypotonic solution

• Solution with lower solute concentration compared to cell

• Water moves into the cell where the concentration is higher

• Low osmotic pressure

Hypertonic solution

• Solution with higher solute concentration compared to cell

• Water leaves the cell toward higher concentration environment

• High osmotic pressure

pH

Degree of acidity or alkalinity of a solution

Obligate anaerobes

Microorganisms that lack enzymes for processing toxic oxygen & die in its presence

Obligate aerobe

Microorganism that can’t grow without oxygen

Microaerophiles

Microbes that are harmed by normal atmospheric concentrations of oxygen but require a small amount of it in metabolism

Facultative anaerobes

• Microbes that don’t require oxygen for metabolism but use it when present

• Can grow anaerobically

Aerotolerant anaerobes

Microbes that don’t use oxygen but can survive & grow to a limited extent in its presence

Fluid thioglycolate medium

Liquid medium that can be used to support the growth of aerobic & anaerobic organisms

Catalase

• Enzyme that detoxifies reactive oxygen species

• Converts hydrogen peroxide into water & oxygen